Fur t h e r
C o n ce r n i n g
R e s e a r ch e s
We ig h t
Ato m i c
s
of
Po t a s s i u
m
S i lv e r
,
N i t roge n
C hlo ri n e
,
B ro m i n e
S ul p h ur
and
,
,
B"
W I LL I A M
T H EO D O RE
IN C O
A RT H U R
ED
ST
LL
AE H L E R
A
,
R
B O RA T I O N W I TH
G E OR G E
WA R D M U E LL E R
,
A ND
,
s
e
P RI L
,
1 90 7
S H A NNO N
FO R B E S ,
G R I NNE LL J O NE S
WA S H I N G T O N D
P u bl i s h e d b y t h C a r n e g i e I n t i tut i
A
I C H A RD S
.
C
on
.
:
of
W a h i n gt o n
s
,
C A R NE G I E I N S T I T U T I O N O F W A S H I N G T O N
P U B L I C A T I O N NO 69
.
C O NT R I B U T I O NS
I
F ROM T H E C H E M C A L
OF HA R
V A R D CO L LE G E
3
P
uss
or
¢
B"
g 3
S
RO N
WA S H I N G T O N
,
A D AM S
.
D
.
c
.
L A B O R ATO R "
C O N T E NTS
A
R
T HE AT O M I C WE I GH T 0 F P OT A S S I U M ; T H E A N A LY S I S OF
C H L ORI D E B " T W R I C H A RD S A N D ART H U R S T A EH L E R
EV I S I ON
OF
SIC
In
.
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t du ti
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h g
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t i c Ch l o ri de
Th e D ry i n a n d W e i g i n o f t h e P o ass i c
i n o f Arg
ge n
Th e P re ci p i a i o n a n d We i
Th e R a i o o f P o ass i c t o Ar e n i c C l o r i d e
Th e R a i o o f P o ass i c C l o r i d e t o S i l v e rr
D i s c ss i o n o f F i n a l R e s l s
S mm a r y
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e
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c
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Po
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P OTA S
on
c
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T HE AT O M I C WE I GH T OF P OT A S S I U M ; T H E A N A LY S I S OF
B RO M I D E
B " T W R I C H A RD S A N D E DW A RD M U E LL E R
tr d u t i
Th P r p a ra t i
Th S u r
o
h
h
.
OF
SIC
In
t
t
gh g
g t
a id
0
c
Wa t r
C
e
L a b o ra t o ry
U tens i ls
Th e D r y i n g a n d W e i gh i n g o f P o t ass i c B r o m i d e
Th e P r e ci p i t a t i o n a n d W e i gh i n g o f Ar g e n t i c B r o m i d e
Th e R a t i o o f Arg e n t i c B ro m i d e to P o t ass i c B ro m i d e
Th e D e t e rm i n a t i o n of t h e S i l v e r Ne e d e d f o r P re c i p i t a t i o n
Th e R a t i o o f P o t ass i c B r om i d e to S i l v e r
Th e At o m i c W e i g ht o f P o t ass i u m
Th e
u
S mm a ry
TH E
Y N T H E S I S O A GE N T I C NI T T E
N
OGE N
B " T W RICH A DS
S I L VE
Q U A N T I T A T I VE
WE I GH T S
OF
NI T R
tr du ti
P r p a ra t i
f P ur
N i t ri A i d
In
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Ma t e r i a l s
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Th e S y n
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e
of
Arge n t i c
Ni
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.
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T H E AT O M I C
G S F ORB E S
A ND
A ND
.
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4
CO N
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Th e P r i y o f t h e F s e d A r e n i c N i r a
Te s s f o r D i ss o l ve d A i r
Te s s f o r R e a i n e d Wa e r
Te s s f o r n s o l b l e m p r i i e s
Te s s f o r A m m o n i c N i ra e
Te s s f o r N i r i e
Te s t s f o r F r e e A c i d
s R e l a i on s t o th e
Th e F i n a l R e s l a n d
t
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Valu s
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6 4-6 5
L E C U LA WE I GH T O A GE N T I C S U L P H AT E A N
B " T W RICH
DS N
S ULP H U
I t du ti
P l i m i a ry E x p r i m t s
f P u r Ma t r i a l s
Th P r p a a t i
A id
S u lp hu r i
Arg t i S u lp h a t
H yd
h l ri A i d
f A g ti
Th F u s i
S u l ph a t
f Ar g t i S u l ph a t i t C h l r i d
Th C v s i
Th F i a l R s u l t s
Th At m i W i ght f S u l p hu r
S u mma y
re
of
S il v e r
TH E MO
n ro
At o m i c We i ght s
o
c
e
n o
o
e
T H E AT O M I C WE I GH T
G R IN N E LL J O N E S
D
.
0F
A R EV I S I O N
O F TH E
A T O MI C
TH E A NA L "S I S
B"
T H EO D O R E WILLI A M
OF
WE I G H T
OF
P O TA S S I U M
P O TA S S I C C H L O R I D E
R I C HA R D S
AN D
C ON T RIBU T I ONS F RO M T HE CHEM I C A L L A B O RA T O RY
A R THU R
OF
H AR
S TA EH L E R
V A R D C O LL EGE
A
R EV I S I O N
O F TH E
WE I G H T
A TO M I C
OF
P O TA S S I U M
.
TH E A NA L "S IS O F P O TAS SI C C HL O RIDE
.
I NTRO DU CTI O N
.
The atom ic weight o f potas sium is a chem ical constant o f unu sual inter
est and s ignificance S tanding as it does in the middle o f t h e se ries o f
five ato m ic weight s o f the m ost ele ctro positive m etal s
substances
w hich exhibit in a highly m a rke d degree both s i m ilarity and progressive
change in properties
thi s numbe r mu st be o f u nu sual importance in the
search fo r that undiscove red mathematical relationship w hich u ndoubtedly
exists be t w een these constants M oreove r the atomic w eight o f p otassiu m
i s essentially bound up w ith the ato m ic w eights o f oxygen chl orine and
s il v e r thi s grou p f orming a f undamental basi s in the cal culation o f nearly
all the othe r atomi c w eights ; so that a change in th e ato m i c w eight o f
pota ss iu m has a w idely r a m i fie d e f fect on the whol e tabl e o f ato m i c
w eights I f any fu rthe r evidence o f this f act w e re needed th e recent
pape r o f R W G ray would f u rnish it
The recent investigation upon th e atomic weight o f sodium b y one o f
2
us in conj unction w ith D r R C Well s showe d conclu sively that S ta s s
wo rk upon which reste d earlier knowl edge w as somewhat at fault in
se v eral resp ects The m ost se riou s o f these e rro rs were first th e existence
o f impu rity in S tas s sil v er ; secondly the fact that in his wo rk sol id salt
w a s dropped into the argentic solution cau sing occlu sion o f salt ; and
thi rdly inadequate knowl edge concerning solutions o f a rgenti c chlo ride
In V ie w o f these e rrors it seemed not im po s sibl e that a simila r revision o f
p otassium might l ikewi se yiel d S l ightly lowe r re sults for potassium than
had been found by thi s master o f exact analysi s F o r this reason t he
p res ent investigation w a s undertaken
B e fore des cribin g the p resent work a brie f hi s to rical review o f pre viou s
investigation s may not be ou t o f place The determinations may b e
di v ided into t w o grou p s — the first group including all o f these dete r
m i n a t i on s in wh ich th e molecula r weight o f a pota ssi c halide w a s found
by decomposition O f a chlo rate b romate o r iodate and the secon d grou p
thos e in wh ich data f or determination o f th e relation o f potass ium to
.
,
,
-
.
,
,
,
,
.
,
1
.
.
.
’
.
.
.
,
,
.
,
,
’
,
,
.
,
.
.
.
,
W
ay J u C h em S oc
h a ds
s Car g i e I st
G r , o rn
R
2 Ri c
r
a n d We l l
S o c , 2 7 , 4 59
em
1
.
.
Ch
,
.
.
.
.
,
.
n
ne
Ze i ts
.
.
of
an o rg
.
Tra n s
89, 1 17 5
i n on P bl i c
e m , 4 7 , 56
,
Was h gt
Ch
,
,
u
at i o
n
28 ;
Jou r
n
.
Am
.
8
TH E A N A
LY S I S
P O T A S S I C C H L O R I DE
OF
.
chlorine bro m ine or iodine w ere obtained The second grou p alone i s
concern e d with the pr e sent work
The e a rly w ork o f B e rz e l iu s F e louz e a nd M a rign a c need s carc e ly b e
considered here
It d e al t f o r the m o s t part with the p reci p itation o f
argentic chloride f ro m a solution o f potassic chlo ride and gave very
w idely discrepant results E v en the l a ter w ork o f Marignac on chlo ride
bro m id e and iodide o f S il v er w as o f doubt f u l v alue especially the l ast ;
and accordingly until the pre sent resear ch w as unde rtaken the atomi c
w eight o f pota s siu m rested ch iefly on the a nalyses of potassic chloride
m a de by S tas by R ichards and Archibald and by A rchi b al d alone and
upon the analysis of potassic bromide made by S tas
A S in the case o f sodiu m S t a s made seve ral se ries o f d e ter m inations
o f the amount o f S il v e r needed to precipitate a kno w n a m ount o f p otass ic
chloride One of these se ries was m ade in 1 86 5 a late r one in 1 881 and
yet a nother S hortly be f ore his death The earliest series although in
some respects mo re care ful and tho rough than the later ones was greatly
at fault becau se in it he overlooked the solubil ity o f argentic chloride
Acco rdingly o f this w ork only the late r need be conside red The mean
o f seventeen analyses indicated that 1 0 0 parts o f S il v e r w ere equ ivalent
to
p arts o f potas sic chloride corresponding to an atomic weight
for potassium o f
i f silver i s taken as
and chlorine as
3
L ater R ichards and Archib a l d found as a S ide issu e o f a research upon
the a to m ic weight O f c ae sium that 1 0 0 parts o f S ilve r correspond to
parts o f potassic chlo ride and al so that 1 0 0 parts o f a rgentic chlori de
correspond to
parts o f potassi c chloride ; and still more recently
“
Archib a l d f ound results not v ery di ff erent With the values given a b ove
fo r sil v er and chlorine these results indicate a valu e fo r potas sium o f
and
respecti v ely in the case O f R i cha rds and Archi bal d
and
and
respectively in Archibal d s resea rch
In the case o f the b romide S tas found in an unu sually va rying seri es
o f experi m ents that 1 0 0 pa rt s o f silver neede d
parts o f p otassic
bro m ide f or c o m pl ete p recipit a tion a resul t not v e ry far f rom that o f the
l es s pr e cise e a rly w ork o f Marignac I f B a xte r s v alue f or bro m ine is
a ccepted
thi s co rre s ponds to an atom ic weight for potassium
Of
noticea b ly h ighe r than the results fro m the chloride At that
tim e the discrepancy di d not appear becau s e the ato m ic weight O f chlo rine
.
,
,
.
,
,
1
.
.
,
,
,
,
,
,
,
,
.
2
,
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,
,
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,
,
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,
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,
,
,
,
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,
,
’
.
,
,
’
.
.
,
1
a b i f d i s u ss i o
For
r e
c
n of
ut
th i s
w or
k C l a rk s
a l cu l a t i o
’
Re c
n
of
m ay b e c on s l e d
2
a l s o O e vr e s P os
S as Me m Acad R oy B e l g , 4 3
p 42
S e e C l a r e s R eca l c l a i o n
S p ri n
3
P ro c A m Acad 3 8 , 443
R i c a r ds a n d Arc i b a l d
C em 3 4 , 3 53 1 90 3
4 Arc i b a l d Tra n s R o
1 0 I I I , 47
y S oc C a n ada
5 B ax e r
J o rn Am C e m S oc , 2 8 1 3 22
,
( 1 89 7 ) p
t
.
41,
’
,
g
h
h
t
.
k
.
h
.
,
’
h
u
u
u t
.
.
.
.
,
,
.
.
.
.
.
.
.
h
.
.
,
.
,
.
.
,
th e
At o m i c W e i ght s
thu m s d i t d b y W
Z it
o g
e
,
e
e
e
.
an
r
.
.
I N T RO D U C TI O N
9
.
wa s not p roperly evaluated S tas b el ieving that his wo r k on the chloride
al s o indi cated an atomi c weight above
In vie w o f the fact that these resu lts diffe r among one anothe r to an
e xtent beyond a reasona b l e l imit o f experimental erro r it s eemed a d v i s
abl e to investigate once mo re the atomic weight o f p otass ium in o rder to
detect the cau se o f the dis crepancy Thi s appeared to be especially desi r
a b l e o n account o f the recent gain in kno w l edge conce rning the pecul iari
t ies o f arge ntic chlo ride in solution Acco rdingly th e p re s ent research
w a s begun and S imultaneou sly a nothe r concerning potass ic bro m ide A
des c ription o f the latt e r inve stigation follo w s i m mediately a f te r this one
An investigation u pon atom i c weights natu rally resolves itsel f into
seve ral di ff e rent portions — fi r s t the p reparation o f the pu re m aterial ;
second the m etho d o f d rying an d w eighing this mate rial ; third th e
de tail s o f the analysis and the calculation o f the results These w ill b e
conside red in o rde r in the fol lowing page s
,
,
.
.
,
.
,
.
,
,
,
.
1
.
I
P REPARAT O N O F THE
MATERIAL
PO T A S S I C C H L O RI DE
.
.
methods o f p reparing potas si c chlo ride we re tried the most
e fficaciou s b eing a dopted Th e p robl em of cou rse was to e f fect the
el imination o f othe r m etals and othe r acids especially thos e o f the same
groups B oth ends are most qu ickly and completely attained by inco r
po r a t i n g into the p ro cess o f pre p aration su ccess i ve crys t al l ization o f
d i ff erent salts in o rder to eliminate by th e crystall ization o f one sal t an
isomo rphou s su b stance which might ha v e b een retained du rin g the crys
t a l l i z a ti o n o f anot h e r sal t
Th e commonest salts o f p otas sium were
the r e fo re stu died in relation to thei r fitnes s for the el imination O f impu r
ities in thi s way
I n the first place on account o f the goo d results w hich R ichards an d
Well s h a d attaine d in preparing p u re sodic chloride from recrystallized
sodi c sulphate by p recipitation w ith g a seou s hydrochloric aci d sulphate
o f potass ium al so w a s early considered Thi s metho d was howeve r soon
abandoned b ecaus e the relative solu b il ities o f potas s ic sul p hate and
chloride are fa r l es s fa v orabl e fo r the p u r p os e than those o f the sodium
salt s Th e method o f A rchibal d who converted sulphate into chlo ride
th rough p recipitation with ba ric c hlo ride i s complicate d and involve s the
d oubl e work o f p reparing pu re bari c chlo ride as wel l a s p u re p otas si c
sulphate Mo reove r it i s not easy to el iminate the last trace o f b aric
sulphate from the resulting salt This al so w a s rej ected
S eve ral
.
,
,
,
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,
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,
,
,
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,
,
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,
,
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,
.
.
1
A
som
d e ut s ch
,
ew
ch
.
h a t l ss d t a i l d s t a t
e
G e s cl
.
e
,
e
3 9, 3611
emen
t
of
th i s
wo
rk h as a p p e are d
,
ht d
i n th e B e r i c
e
.
10
TH E A N A
LY S I S
OF
P O T A S S I C C H L O R I DE
.
w as s tu died — a salt w hich had al ready been
used by S tas for the preparation o f pu re potassiu m material B oth in
N ext potas si c chlo rate
.
crystall ine form and in solubility this salt is ve ry suitabl e fo r the separa
tion o f sodiu m f ro m potassiu m m aterial S odic chlorate crystall izes in
regu l a r crystal s w hich a r e S i x ti m es a s soluble in hot wa ter and sixteen
ti m e s a s solubl e in col d w ate r a s the m onoclini c cry s tal s o f potassi c
chlorate On the othe r hand the data concerning the crystalline f or m
and sol ubil ity o f the chlorates o f rubidium and c aesiu m a re not su fh
cient to enabl e one to m ake any certain prediction w ith regard to thei r
beha v ior and there f o re experi m ents were m ade in orde r to di s co v er
w hether o r not these salts coul d easily be separate d fro m potassic chlo rate
by recrystallization The f ou r salts o f sodiu m potassiu m rubidiu m and
c aesiu m we re m ixed together a nd qual itatively separat e d by f ractional
crystal liz a tion The s o dium w as e f fectively separated f ro m the crystal s ;
but a f te r th ree care f u l crystallization s the c ae s iu m l ine although stronge r
in the mother l iquor th a n at fir s t w as still not absent fro m the crystal s
Indeed neither rubidiu m nor c aesiu m l ines had conside rably diminish ed
therein Acco rdingly this method w a s a l so abandoned
P otassi c nitrate showed itsel f to be m u ch m ore sati s factory in its
beha v ior Its u se fulnes s did not seem at first s o ce rtain as to be a f ore
gone conclu sion especially as S tas had not su cceeded in p reparing a
pa r ticul a rly pu re m aterial f rom this sal t P robably this f ailu re w as du e
to the ci rcumstance th a t he ca rrie d out the c rystall ization in glass vessel s
w h ich o f cou r s e continually introdu ced sodiu m and sil ica The rather
in a dequ a te data conce r ning the f ou r nitrates may be wel l put togethe r
a s follows :
.
.
,
,
.
,
,
,
.
,
.
,
,
,
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.
.
,
.
,
.
So
Co
T e m p e tu
ra
r
e
.
l u b ili t i n
ld
y
1 00
p a ts
r
of
w
a te
r.
W a me
r
.
Pa t
r s
.
T e m p e a tu
r
60
10
1 14
114
r
e
C ry s
r.
P a ts
r
.
Ve
ry
20 0
a
or
m
.
.
m a ny
43
337
t lli n e f
a
Ne e d l e s
Te t r go n a l
.
h d al
h om b i
h d al
Rh o m b o
an d r
R om b o
h
.
e
r
c
e
r
.
.
B e c a use this s eries o f re s u lts i s not enti rely conclu si v e although
pro m ising a S e ries o f c rystall izations w as carried out he re al so
Thi s
series s ho w ed that an ad m ixtu re o f the three other nitrates with a
large excess o f potas s i c nitrate w as nearly al l el iminated by a s few a s
t w o crystall izations The s ep a ration o f the sodium wa s es pecially marked
,
.
,
.
P RE P A RA TI O N
M A T E RI A L
O F TH E
11
.
in the s p e ct r o s c0 p i c tests Th is m ethod there fo re appeare d v ery wel l
su ited fo r the p reparation o f pu re potass iu m mate rial which m ight easily
be con v erted into chl o ride a fte r the ot h e r metals had been el i m inated
P u re potas si c nitrate o f co m m e rce obtained fro m G e rm a ny wa s dis
sol v e d i n a little wate r freed fro m sol id substance s by filtration and
crystal lize d t w i ce in Jena gla s s fl a sks
The sal t was each time freed
1
from the m othe r l iquor in a po rcel ain centri f uge
Th e resulting m aterial
w a s fou r times su b sequently rec r y s tall ized in platinu m ve s sel s and w hirle d
in a platinum centri f uge The pu re c ry stal s w e re now di v ided into t w o
parts ; one part w a s d ried in a v acuu m des iccato r w hil e the other part
w as s u bj ected to yet s i x m o re c rystal lization s and w hi rl ing s in platinum
v essel s
It no w became a qu e s tion ho w thi s nitrate coul d best be conve rted into
chloride The metho d recommende d by S tas o f h eating the sal t with
pu re am m oniu m chl o ri de involves not only the p repa ration o f thi s latte r
salt in a pu re state but also great dange r o f contamination fro m the
vessel whethe r o f platinu m o r porcelain P latinum i s especially attacked
be cause O f the a ction o f the o x y ch l o r i d e s o f nitrogen and o f chlorine Th e
mo re favorabl e metho d appeared to be to con v e rt the nitrate into chlo ride
by repeated evapo ration with hydrochl ori c acid in quartz d i sih e s Thi s
metho d wa s found to have two obj ections In the first place dishe s
large enough f or the ra w m ate rial were not to be had M oreove r the
tendency o f the b ranching crystals to grow ove r the edge o f the dish
cau sed se riou s lo ss O f material and danger o f im pu rity Ne ither coul d
p otass ic nitrate b e heate d to a high tempe ratu re with ammonic chloride
or in the steam o f hydro chlo ric acid in quartz dishes ; fo r there i s
2 K S i 0 3 + 4 NO 2
0
always dange r that the reaction 4 K NO 3 + 2 S i 0
2
woul d o ccu r
B ecaus e S tas ha d ne v er been a b l e to obtain a sal t f ree from S il ica when
w o rking in glas s v es sels w e desi red to a v oid compl etely the us e o f glas s
There fo re only one way remained namely to con v e rt the potass ic nitrate
into chlo ride by p re cipitation with hyd ro ch l o ri c acid in a platinum dish
The resultin g a q u a regia mu st natu rally attack the p latinum but we p re
fe rre d this i m pu rity to that o f S il ica and found m o reover that the amount
o f p latinu m dissolve d i s very smal l In the p re sence o f large m ass es
o f po t a s s i c salts
a q ua regia espe cially in th e cold di ssolves platinum
bu t l ittl e F o r exam pl e in one experi m ent in whi ch about hal f a kilo
gram o f potassi c nitrate was treated with hydrochloric aci d ga s onl y
th ree tenths o f a gram o f platinum w a s conve rted into the form o f
p otassi c oh l o r pl a t i n a te I n subsequ ent c rystallizations th e amount w a s
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2
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2
2
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‘
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-
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h a ds J u r A m C h m
h a rds d Ar h i ba l d l
Ric
2
Ri c
1
r
,
o
an
n
.
e
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c
.
-
,
oc
.
S oc , 2 7 , 1 0 5
.
ci t
.
12
TH E A N A
LY S I S O F PO T A S S I C
C
H LO RI DE
.
ve ry m u ch less bec a use the great mas s of the nitri c aci d was el i m inate d
by the first crystallization A f te r the thi rd recrystall ization the d i ph e
n y l a m i n reaction f ail ed to re v eal the pres e nce o f any retained nitrate
The p recipit a tion was c arried out in the follo w ing manner : The often
recrystallized ve ry pu re pot a ssi c nitr a te w as dissol v e d in the least possibl e
qu a ntity o f col d w ate r contained in a platinu m di s h packed in ice
S lo w ly in orde r to pre v ent w a rm in g hydrochloric acid gas was run into
this solution The gas w as sup p l ied by w arming a pu re concentr a ted
solu tion and was passed into the nitrate solution through an inverted
platinu m funnel The potassic chloride which appeared so m e w hat yello w
from its sl ight platinic i m pu rity was whirl ed in the p latinum centri f uge
and dis sol v ed in pu re s t w ate r P ota s si c oh l o r pl a ti n a t e i s p ractically insol
uble in a concentrated solution o f the chl oride as the law o f co n ce n
t r a ti o n e ff ect and the theory o f ionization p redicts ; hence the impu rity
was eas ily se p arated upon a small pure filter Th e cl ear col orl e s s S olution
w as again satu rated with h y drochlori c acid and th e sa m e round o f oper
a t i o n s repeated
U pon a third repetition o f thi s proce ss the nitri c acid
w a s el iminated and the salt a s a rule was wholly colorle ss in consequence
On no occasion e v en w ith l arge a m ounts o f materials did perc e ptible
colo r re m ain a f ter fi v e tre a tm ents No specimen w as subj ect e d to les s
th a n seven su ch recrystal lizations while so m e was passed yet five ti m es
mo re through the p recipitation and centri fugal drying Assu m ing that
e a ch ti m e about th ree qua rters o f the o rdinarily adhe ring mothe r liquor
w as remo v ed by the centri fugal separation these crystal s m ust ha v e been
as free f rom hete ro m orphous sub s t a nces as i f they had been r e c r y s t a l
l i z e d m any thousand times in the o rdinary fashion
It w ill be sho w n that
a ll the s a m pl es ga v e the same results u pon analysi s hence fu rthe r pu ri
fi ca t i o n a cco rding to this method was needl ess
The s a lt was found to
be w holly f ree from sodiu m by a sensitive s pe ct r os c0 pi c test It was in
e v ery case freed fro m aci d by a s ingl e recrystalliz a tion from the pu rest
w ate r and by fu s ion in the manne r to be describe d late r
S even di f fe rent sa m pl e s were prepared after this f ashion from varying
ra w m aterial Thes e are given in the l ist b e lo w
“
”
( a ) The pu re potassi c material ( C P o f G erman p reparation ) was
recry s tall ized as nitrate six times and p recipitate d as chl oride se v en times
Thi s sal t a f te r the final recrystallization f ro m pure water w a s dried in a
platinum dish at 1 2 0 in an el e ctri c oven The salt was sno w white and
w as a s clear as wate r w hen fu sed as indeed w e re all the other sample s
This
sa
m
ple
w
as
s
i
m
ilar
to
a
but
obtained
by
the
e
v
aporation
o
f
I
?
( )
the final aqu eou s mother l iquor decante d f rom a Th e mothe r l iquor from
b w as rej ected
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P RE P A RA TI O N
M A T E RI A L
O F TH E
13
.
( 6 ) F i v e extra p reci p it a tions w ith hydrochlo ric gas ( o r t w elve in all )
yi el ded this salt which was p repared fo r analysis in the s a m e wa y as a
This
salt
bore
the
same
relation
to
c
that
b
bo
re
to
a
being
essen
d
( )
t i a l l y identical with c
( e ) F o r this sampl e and the next one th e nitrate wa s recry stallized
twelve times and the chloride p recipitated s even ti m es
( f ) F rom th e final mother l iquo r of e f was prepa red as I) f ollow e d
a fte r a
m
This
sampl
e
was
exactly
l
ike
except
that
the
ra
w
material
ca
e
a
2
( )
from an enti rely di f ferent sou rc e
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A RG E N
TI C
N
IT RA T E
.
The nitrate o f silve r u sed fo r precipitating chlorine in the analy sis w a s
c rystall ize d th ree times from pu re dilute nitri c acid solution and each
time centri fugally freed from mothe r l iquo r B e fo re each a n a l v s i s the
a q u eou s sol ution o f the salt was teste d in the neph elometer for a possible
trace o f argenti c chlo ride and no m aterial was e v er u sed which showed
to this excee dingly sens iti v e test the least trace o f i m pu rity F o r preser
vation in a pu re state it w as kept in a tight desiccato r o v e r potash
.
1
,
.
.
S
IL V E R
.
The metall i c s ilve r u sed i n the rese a rch was made fro m a rgentic nitrate
whi ch had been S i x times recrystall ized The metal w as p recipitated a s
fine po w de r by ammoni c for m ate m el te d on pu re l ime and fu rth e r
3
pu rified by el ectrolys is
Th e beau ti ful c rystal s thus p repared were fused
in a strea m o f pu re ele ctrolyti c hyd rogen and final ly in a va cuum o f
mm The metal was supp orted on a boat o f the pu rest l i m e p repared
f ro m cal ci c carbona te p re cipitate d f ro m th e nitrate for thi s pu rpose
Th e boat wa s p rovided w ith seve r a l com pa rt m ent s e ach o f whi ch hel d
c
enough S ilver for one analysi s in orde r to a void the poss ibl e i n t ro d u
tion o f impu rity into the metal by sub sequ e nt cutting I t was inclosed
in a stou t po rcelain tube p ro v i ded w ith H empel w ater c ool ed stoppers
4
and was heated el ect rically in a H e r a e us tube fu rnace
The vacuu m
driven G e r yk oil ai r pu m p E xcept fo r these
w a s maintained by a mo tor —
m ino r impro v ement s the p repa ration w as es sentially s i m ila r to the best
methods e m ploye d by R ichard s and W ell s in thei r o ften —
cited w o rk to
w hich the reader i s re f erred fo r f u rthe r detail s
.
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i h a r ds P ro c A m Acad 3 0 3 85
2
R i ch a r ds a n d W e ll s J o u rn A m C h e m
L H o s ky n s A b r a h a l l J o u r n C h e m
1R c
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ad
P r o c A m Ac
4
H e ra e u
s, Ze i
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2 8, 22
t f
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E le
kt r h
oc
Ze it
,
i
em e,
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8, 20 1
S oc , 2 7
S o c Tr
.
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a n o rg
.
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Ch em
.
,
8 , 26 9
47 5
,
a s
n
.
6 60 ;
al so
h a rds
Ric
.
14
TH E A N A
N
IT R I C
LY S I S
A ND
OF
P O T A S S I C C H L O R I DE
H YDRO C H LOR I C
I
A C DS
.
.
care fully tested preparations o f com m e rce w ere u sed as the raw
m ateri a l s in the p reparation o f these acids
They w ere redistill ed with
platinu m condenser s u ntil they w e re f ully pu re e nough f or the purposes
fo r which they w e re needed The h y drochlori c aci d had been S ho w n
in the rese a r ch on sodium to be free fro m bro m ine o r iodine
V ery
.
.
.
WA T E R
.
This sub s tance becaus e it is u sed in larger quantities than any other
mu st be especially pu re All the water u sed either f or p re p aration o r
analysis was t w ice distill ed once with alkal ine p ermanganate and once
alone F o r the bes t work a platinu m condenser was u sed All that w as
needed fo r analysis w a s tested in the nephelo m eter im m ediately be fore u se
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.
THE DR" NG A ND
I
WEI G H I NG
O F THE P O TAS S
I C C H LO RI DE
.
final p reparation o f the salt for analy s is i s given a special chapter
to itsel f because the p roper execution o f thi s f eatu re i s o f ve ry great
import a nce not l es s than the p u rification o f th e m aterial I t is clearly
useless to separate
per cent o f a metalli c i m purity i f
p e r cent
o f w a ter i s allowed to re m ain in the salt
Ob v iou sly superficial drying can not remove the I mpr i soned m oistu re
in the crystal s hence they m u s t be f used
E xcept in a f e w prel i m inary
expe ri m ents where a co m m on platinum cru cibl e was u s ed this f usion
w as conducted in a pl a tinu m boat o r open bottle contained in a porcel a in
tube th rough w hich a cu rrent o f nitrogen was p as sing The experience
in a nu m be r o f si m ilar cas e s that the simult a neou s p resence o f oxygen
and traces o f hydrochloric a cid inclosed in the crystal s i s l ikely to cau se
pe rce p tible corros ion o f the p latinu m boat w as confirmed in this case ;
hence an inert gas w as needed The nitrogen w a s p repared by the w ell
kno w n m e thod o f Wa n k l y n by pa ss ing ai r charged w ith a mm onia
o v er red hot coppe r The exces s o f a mm onia w as c a re f ully el i m in a ted
by washing the ga s with m uch dilute aci d B ecause fu sed sodic chloride
was found to be e ssentially free f ro m dissol v ed nitrogen w e did not think
it n e cessary to f us e this v ery sim ilar potassiu m salt in a vacuu m
P otassi c chloride al though not s o hygros copi c a s som e othe r salts
used in si m il ar researches is neve rtheless fa r too hygro s copi c to weigh
sa fely w hen directly ex p ose d to the ai r o f the bal ance roo m Its ten
d e n cy to attract w ate r w as s een in perceptibl e c rackling wh en th e tube
Th e
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1
h a r ds Z i t p h ys C h
Ric
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e
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em
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,
4 6 , 1 89
TH E DR
YI N G
A ND
WE I G H I N G
O F TH E
P O T A S S I C C H L O R I DE
15
.
containing fu sed salt was opened in th e moist at m o s p he re o f th e beake r to
be u sed fo r the solution of the salt
At first the bottl ing apparatu s s o o ften u sed i n the C hemical L a boratory
o f H a rvard C ollege was em p loye d to p rotect the fu sed chlo ride from mois
tu re du ring the determination o f its wei gh t the chloride being contained in
a pl atinum boat p rotected by a glas s stoppe red weighing b ottl e B ecau se
however the w eighin g room w a s not wholly constant in te m peratu re o r
in m oistu re time and trouble we re needed to obtain exact weigh ings even
al though the a pp a ratu s was always weighed by substitution aga inst a
s i m ilar e m pty boat and bottle The u se o f quartz w eigh ing bottl es proved
to be no advantage indeed i f anything a di sadvantage In eithe r case
i f ti m e enough were taken satis f acto ry w eighings coul d be m a de ; but
a s ti m e was especially p reciou s another devi ce w a s u sed which wholly
ove rcame t h e trou b le
Thi s e f fective and satis facto ry devi ce consisted i n the u se o f small
weighin g bottles o f platinu m S ha p ed l ike the long L aw rence S mith
cru cibl e which w ere closed by smal l platinum capsul es fittin g into the
bottles l ike ground stoppers One o f thes e bottl es containing the p otassi c
chlori de w a s sup p orted by a loop o f platinu m wi re in an incl ined po r ce
lain tube and above it in the tube was p l aced i t s platinum stoppe r G l ass
stoppe rs fitted into each en d of the porcel ain tube whi ch was enci rcled
by a su itabl e f u rnace A fte r the p otassi c chlo ride had b een dried for
a long ti m e at a high te m peratu re j ust b a rely f use d in nitrogen and
coole d in a cu rrent o f p u re dry ai r the stopper w as S haken into p lace
and the platinum bottl e q uickly remove d and place d in a desi c cato r
This arrangem ent i s e ssentially S imilar to the bottl ing arrangement o f
R i chards and P a rke r except for the additional advant a ges that gl ass
i s wholly el i min a ted and that the inclo sed ai r volu m e in the tube i s mu ch
small e r
P ro b ably the b u rni s hed pl a tinu m j oint i s not a s tight as the
ground glass j oint ; but it is amply tight enough to p revent any a ppr e
c i a b l e di ff u s ion o f m oistu re du ring the very b rie f ex p osu re o f th e tube
This w a s evi dent from the constancy o f the weigh ings which were made
by substitution against a simila r em p ty p l atinum b ottl e kept in a S i m ilar
des iccato r The weighings were ve ry q u ickly p e rformed and were tru st
worthy B e fore b eing u sed the p latinum b ottles we re re p eatedly i g nited
w ith pu re subl i m e d ammo n i c chloride in o rder to remove i ron ; they
remained satis factorily constant in w eight du rin g su b s equ ent exp eriments
the one u sed fo r the fusion losing only
m g in fou rteen experiments
o r on the ave rage
m g in a singl e e xpe riment In one experim ent
whe re oxygen w a s p res ent du ring t he fus ion as m uch a s
m g was
taken f rom the boat the platinum being plainly visibl e on solution Thi s
was o f cou rse not us e d fo r analysis
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16
TH E A N A
LY S I S
P OT A S S I C C H L ORI DE
OF
.
Al l w e ighings w hether o f thi s s alt o r o f s il v er o r argentic chl oride
w e re m ade by s ub s titu t ion in the m anner al ready described in other
papers
The balance was a short a r m ed instru m ent made by Tr o e m n e r
o f the type adopted in othe r S imilar investigations ; it w as u sed only fo r
this w o rk and t h at to b e described a f ter w ard The weights w e re o f
pl a tinized brass care f ully standardized according to th e u sual H a r v a rd
m ethod
Al l w eighings we re redu ced to the v acuum standard Thu s f rom e v e r y
a p parent gra m o f sil v e r
gra m wa s subt racted and to ev e ry
a pparent gra m o f a f ge n ti c chloride
wa s added i f the tem per a
tu re was 2 0 and the pres sure normal Assuming the density of potassi c
chlo ride to b e
the similar co rrection for this salt was
C h a nges in te m peratu re and p ressure o ccasional ly cau se d S light bu t
3
u sually inessenti a l changes in these co rrections
The w holly colo rles s t ransparent f u sed s alt w as di s s olved in the pu rest
w ater in a cove r e d beake r o f Jena glas s under a tightly fitting bell j ar
The solution was al w ays perfectly cl ea r except in the rej ected case already
cited an d one oth er S i m ilar one A f te r this solution had been very thor
oughly washed a w ay and u s ed fo r analysi s th e platinu m w e ighing bottl e
w as heated fo r a short time in anothe r crucible a nd w e ighed in prepara
tion for anoth e r analy s i s The constancy o f the s e w eighings has a l r e a d v
be e n discu s s ed
The det a ils o f preparation ha v ing been d e scribed the analytical methods
th e m s elves mu st b e indicated The p robl e m w as as in the case o f s od iu m
to deter m ine the a m ount o f chlo rine present the weight o f potas s iu m
being found by di ff erence Both o f the p re v iou sly u s ed m ethod s f or
finding the a m ount of chlo rine w e re u sed and th e d e tail s a re so mu ch
li k e those di scu ssed by R ichard s and Well s that mu ch may be a ssu m ed
as u nder s tood F o r a f ull under s tanding o f the present w ork that upon
sodium shoul d be read in connection w ith it
The t w o m ethod s f o r th e dete r m ination o f chlo rine na m ely the weigh
ing o f the pre cipit a ted argenti c chlo ride on the one hand and the di s
a re discu ss e d
co v e r y o f the equi va l ent a m ount o f sil v er on t h e oth e r
bel o w in o rde r
,
,
1
-
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4
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h a ds d R g rs Z i t
g Ch
2 7 465
A m Ch m S
d W l ls J u r
Ri h a ds
2 2 1 44
Am Ch m S
Th s
R i h a ds J u r
d si ty f
Am Ch m S
2 7 465
d W l ls J u
R i h a ds
1
F or
c
2
4
e
r
,
o
Ric
see
e
an
r
c
en
3
xam p l
e
n
,
n
o
.
o
e
.
e
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an
r
.
oc
.
,
e
e
,
oc
.
.
a nor
.
L oc
an
r
.
ci t
.
e
,
o
rn
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e
,
e
.
oc
e
,
,
o
c
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,
,
e
m
.
,
wei
a l so
1 0 , 19
gh t s h ad
an
av rage
e
18
TH E A N A
LY S I S
OF
P O T A S S I C C H L O R I DE
.
a bly b e cause o f lo s s o f p r e v iously adsorbed water Moreove r w hen a
dilute solution o f arge ntic nitrate potassi c nitrate and nitric acid such as
re m a ins a f ter an a n a ly s i s w as p a ssed through the filte r and this was five
ti m es w a s hed w ith w ate r and dried at
yet
mo re was gained
p rob a bly d ue to adsorb e d salts
V e ry tho rough wa s hing a f te r this
b rought the cru cibl e ba c k to its original w e ight a f ter drying at
The s e e x peri m ents sho w ed that the w ashing o f th e platinu m sponge
mu st be ve ry thorough and that a definite te m peratu re m u s t a l w ays be
u s ed for drying Ot h e r experi m ents s ho w ed that constant w eight cou ld
.
,
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-
.
,
.
always be obtained i f these conditions were fulfilled
It is wel l kno w n that argenti c chlorid e sometim es cl ings to a platinum
su rface and always sh rinks m uch on drying On this account the
so m e w hat delicate uppe r s u r f ace o f the sponge w as protecte d by a closely
fitting disk o r di a ph ragm o f pl atinu m punched w ith many fine holes
This di a phr a gm m e rely lai d upon the top O f the sponge at the base o f the
c ru cibl e wa s easily loo s ened w ith the p recipitate and f orme d an e f fectual
p rotection f o r the sponge A f te r thi s w as done no platinu m was e v er
lo s t fro m the uppe r su r f ace ; and none w a s e v er carried a w ay m echanically
fro m belo w in the w ash w ate r
I n spite of the p resence o f the disk small parti c les o f argentic chloride
al w ays clung here and there to the sponge A S a p os sible means o f
re m oving th e se w hen prepa ring f o r a ne w analysis potassi c cyanide was
tested It w as f ound ho w e v e r that not only w a s this salt adsorbed by
the sponge but th a t in the p resen c e o f ai r platinu m w a s di s sol v ed e v en
to th e extent o f a milligra m
a fact not ne w but none the l e ss pertinent
Thiosulph a te was not tried becau s e sulphu r w a s an i m pu rity l ittl e wi shed
F inally w hile a m m onia f or a S hort time w as ine f ficient th is l iqu id when
con c entrat e d and a ppl ied f o r t w elve hou rs or m ore dissolved every trace
o f t h e s ilv e r s alt without harm ing the c ru cible
Th e techniqu e o f the G ooch M unroe cru cibl e having thu s been mas
t e r e d thi s utens il w as us ed w ith satis faction as a m ean s o f collecting
and w eighing the pre c ipit a te in hand The latte r w as fir s t w ashed o ften
by d e cantation a s i s recounted b e lo w and finally on the filtering crucibl e
w hich was dried to con s tant w eight by a te m p e ratu re gradu a lly ri sing to
A fte r c a re f u l weigh ing the main m as s w as separated from the
clinging platinu m disk and w as c a re f ul ly fu sed in porcel ain as h a s O ften
been described The accu rately dete r m ined loss on f usion amounting
so m eti m e s to a milligram w as c a l cul ated f ro m the part to th e w hol e
and appl ied as a correction to the total weight o f the p recipitate
Thi s w eight e v en as thus co rrected did not howeve r exactly represent
t h e total in w e ight of the chlorine as s o m e o f the arg e nti c chlo ri de was
d i s sol v ed by the w ash w ate r
Th e a blution had been condu cted in th ree
.
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TH E
P RE C I P ITA TI O N
WE I G H I N G
A ND
O F A RG E N
TIC
C
H L O R I DE
19
.
stages j ust as in the o ften cite d inve stigation o f sodiu m The first stage
inclu ded the mothe r liquo r a nd first fi v e w a s h w aters cont a ining i n t e n
t i on a l l y as m u ch argentic nitr a te as the mothe r l iqu o r and added to re m o v e
th e greater part o f the potassi c nitrate Thi s first quantity o f l iqui d wa s
enti rely f ree from chlorine in eve ry accepted analys is as was shown by
care f ul testing in the nephelo m ete r and so w as at once cast aside
The second stage o f washing wa s condu cted with very dilute nitri c
acid and yiel ded
or
l ite r o f a v e ry d ilute solution o f m ixed nitri c
a cid and argentic chlo ri de and nitrate The trace s o f chlo ride wh ich it
contained we re careful ly estimated in the nephelo m ete r a f ter addition
o f excess o f argentic nitrate
The thi rd stage o f th e washing also condu cted w ith pu re wate r a cidifi e d
with nitri c a cid to p revent colloidal i rregul ariti e s yiel ded a l ite r o r mo re
o f li q u i d containin g much argentic chloride The analysis o f this l iqu id
constituted a ve ry important p a rt o f the w o rk and ga v e mu ch t rou ble
In orde r to b e as certain a s p o ssibl e o f the weight o f chlorine it con
t a i n e d th i s l i q ui d was te sted in fi v e cases acco rding to two ve ry di ff e rent
methods The first o f these consisted in e v aporation o f the solution
under di m ini shed p res su re and actual w eighing o f the p recipit a te and
the second consisted i n a new modification o f th e nephelo m ete r test
Al though the l atte r e v idently gave th e more satis f actory resul t s th e
fo r m e r i s wo r thy o f b rie f dis cu ssion becau s e its outco m e certainl y r e p r e
sents the m axi m u m v alu e
In o rder to carry out th ese t w o pa rallel quantitative tests the collected
wash wate r wa s divided into two pa rt s ; and th e large r pa rt about 9 0
p e r cent o f the whole was evapo rate d unde r lo w p res su re at 50 in a
specially m ade Jena glas s 2 liter flask w ith a gl as s stopper In the cou rse
o f this e v aporation the a rgentic chlo ride began to s epar a te out when the
v olu m e ha d been re du ced to about
l ite r i f 2 m g o f th e s a lt w ere
present
a f act agreeing w e ll w ith the re cent obse rvations conce rning this
solubil ity
The d ri ed res idu e was di ssolved in a v e ry l ittl e a m m onia
freshly distil led in pl a tinum and w ashed into a s m al l p recipitating flask
where it was r e p r e ci pi ta te d with exces s o f a rgenti c nitrate and nitric acid
This t ra ce o f p reci p itate wa s coll ected and weighed on a fresh G oo ch
Munro e c ru ci b le in the same w ay as the la rger ma s s The results are
given b elow in compari son w ith those obtained from the same solutions
by the nephelometer
An important modification was int rodu ce d into the nephelometri c dete r
mination One o f u s has repeatedly pointe d ou t that in o rder to obtain
satis factory results w ith thi s instrum e nt th e solution to be tested and
that u se d a s th e standa rd o f co m parison mu st b e treated in exactly the
-
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-
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°
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-
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'
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1
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1
S e e f or
e
xa m p l e
ttg r
Bo
e
,
Z e i t s ch r
.
ph ys C h
.
em
.
,
5 6 , 93
20
TH E A N A
LY S I S
P O T A S S I C C H L O R I DE
OF
.
same way
H ence the u se o f a ground glass plat e as a standard o f
com pa rison is a very qu e stionable proceeding I t appears that the p r e ci pi
ta t i o n o f a rgenti c chlo rid e fro m solutions o f thi s s al t di ff er perceptibly
in m e ch a ni s m f ro m the p re c ipitation o f the s a m e substance f rom other
chloride solution s e v en w h e n argenti c nitrat e in great excess i s u s ed
in each c a se
Accordingly in o rder to s ecu re a per f ectly s atisfacto ry
co m parison both p recipitates m u s t be dissol v e d in a m m onia a nd r e p r e
ci p i ta t e d
Th e precipitate then appea rs in each c a se in p reci sely the same
condition and yiel ds tru s tworthy re s ults
Th e pres e nt t e sts were carried out in the f ollo w ing manner : Two
test tubes o f precisely the sa m e v olu m e
l ite r ) we re provided Into
o n e o f the s e wa s pl a c ed
l iter o f the wash w ater a nd into the other
s er v ing a s the standa rd O f co m p a rison a l ike volu m e o f w ate r containing
about as mu ch car e fully m e a sured chlorine ( in the form o f potas s ic
chloride ) as w as p resent in th e fi rst Into each w as no w ru n 5 m l o f a
three hundredth no rm al solution o f a rgentic nitr a te Th e solutions w ere
s tirred w ith a pl atinu m stirre r p re v iou s ly cl e a nsed with a mm onia and the
pu re s t w ate r A f te r fi v e m inutes the p recipitate s w e re w ell f o r m e d ; they
w e re then both dissol v ed with th e help o f a m ill iliter of freshly distilled
am m oni a and r e p r e ci pi ta te d with a sl ight exces s o f nitric acid being filled
to si m il ar mark s near th e top o f the tu b es The two clou dy solutions
thoroughly sti rred we re allo w ed to stand and compared optically in the
nephelo m et e r in the u sual way
The following tabl e co m pares the results O bt a ine d by the t w o methods
The va rying solub ility o f the hal ide in the wa sh —
w ater w as m ainly due to
di f ference in te m pe ratu re at the ti m e o f the abl ution
1
2
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,
3
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-
,
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-
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,
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,
,
,
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,
.
.
.
Th e C o mpa r i s on
o
We i g h ts
f
o
f A r g e n ti c C h l or i d e f o un d N e ph e l o m e tr i ca l l y
by E v a por a ti o n
E p e i me n t
x
r
No
V l u me
o
.
By
L
t tcr s
.
We i g h t
.
eva p
ora
ti n
o
.
s
of
By
ar
ge n ti c c h l i d e
or
n e p h e l me te
o
r
.
D i ff e e n ce
r
.
3 96
.
0 84
.
.
3 22
1 97
.
.
2 59
.
0 62
.
.
0 90
—O
.
.
h
J u
Am C em
o rn , 3 1 , 2 4 2
2 ‘
VVe l l s , A m C e m
99
o rn , 3 5
3
Ric
r
and
e l l , C rn e i e I n
2 7 , 4 85
.
h a ds
.
.
h
J u
W s a
g
,
29
3 5 , 50 9
.
.
.
.
1 45
1 88
1
and
st
.
Pu
b
.
28
Jou r
n
.
Am
.
Ch e m
.
S oc
.
,
TH E
P RE C I P IT A T I O N
A N D \V E I G H I N G O F A RG E N
TI C C H L O RI DE
.
Thu s the nephel o m ete r al w ays indic a ted l e s s a rgenti c chloride th a n
the gra v i m et ric p rocess At fi r s t the neph elo m ete r w as su s pected but
the steadily diminishing di ff erence between the t w o S e ries o f results indi
ca t e d that they w e re app roaching the point w he re they w oul d indicate
the s a me values A S the nephelo m et ric tre a t m ent w as inva riabl e bu t
on the other hand the e v aporating fl a s k m ight ea s ily be attacked it
s eem ed p robable that th e decreasing di f fe rence exhibited by the figu res
was du e to something adde d to th e weight o f the p recipitate f rom t h e
latter sou rce Apparently a s is reasonabl e the flask wa s les s a nd les s
attacked as it continued in u s e
F o r thi s reason the gra v i m etric results w e re whol ly rej e cted and the
nephelo m etric ones a lone us ed in the cal cul ation o f the final results
.
,
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-
,
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,
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,
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I
TH E RA T O O F P O TASS
IC
ARGENTI C C H LO RI DE
TO
.
The final results o f th e se ries o f analyse s dis cu ssed above are reco rded
in the fol l ow ing table A nu m be r o f p relim inary e x p eri ments are
omitted from thi s table since it is cl ea r that no doubt f ul o r imperfectly
executed expe ri m ent S houl d find a place in su ch a tabl e o f fin a l data
The list is nearly con s ecuti v e ho w ever as bu t fe w expe ri m ents m e t w ith
m i s fortune a fter the p roce sses had been maste red
The original nu m ber
ing o f the expe ri m ents is retaine d ; they w ere reco rde d in the notebook in
ch ronological o rde r All the a rgenti c chloride re fe rred to i n thi s tabl e
was cl ear an d colorl es s ; a f act wh ich i s one o f th e best proo fs that it
was free fro m argentic nitrate o r from o rgani c du st
.
,
.
,
,
.
.
.
F i n a l S e r i es
N
f
P
o
“
55i93 1
’
f D e te r m i n a ti on s
We i g h t
G m
ra
13
14
15
20
31
A
4
5
6
3
4
a
a
a
b
b
v e r a ge
.
.
.
.
.
of
s
.
3 6 82 5
56 7 3 7
41 4 2 4
2 7 21 5
830 2 8
o
f
th e R a ti o K C Z: A g C l
We i g h t
G m
ra
8
10
12
6
9
.
.
.
.
.
s
o
f
A Cl
KC I
=
o-ooo x
t
.
A
.
t mic
o
t re aty:
.
3 9 86
7 03 8
3 3 23
29 1 3
2 87 0
1 14
1 15
1 14
112
52 012
5 2 OH
39
39
39
39
52 0 1 1 8
39 1 134
52 0 l 2
.
.
.
.
.
.
.
.
.
Thi s result will b e dis cu s sed a f te r the next se ries h a s been presented
It ha s a p roba b le e rro r cal culate d by th e m e thod o f l east squa res o f onl y
about
acco rdingly fu rthe r repetition w as deem ed unn e cessary
.
,
,
.
22
TH E A N A
LY S I S
P OT A S S I C C H L O R I DE
OF
I
TH E RA T O OF P O TASS
I C C H LO RI DE
.
TO S
I LVER
.
I n thi s serie s o f exp e ri m e nts weight s o f the pu rest s ilver e qui v alent to
enti r e ly n e w portion s o f f u s ed potassic chloride a s cal cu lated f ro m th e pre
c e ding t a bl e w e re dissol v ed in nitric a c id and the t w o equi v alent solutions
we re m ix e d G r e a t c are w as u s e d Th e presence o f an exce s s o f s ilve r
o r o f chlorine w a s then d e ter m in e d w ith t h e neph e lo m e ter e x a c tly a cco rd
ing to the d e tails o f m anipul ation adopted by R ichards and Wells w hose
l t e d f or particul a rs
accounts shoul d be c on s ulted
Th e tabl e belo w contains
n iinary
n
th e final re s ult s ; the preli m
y ppracti ce experi m ents are o m itted f or the
sa m e rea s on as be f or e
,
,
,
,
.
.
,
,
.
.
F i na l S e r i e s
A
iiiil
P
of
ys i s
.
i
di KCl
r
p ar
o
on
f D e te r m i n a ti o n s
30
32
33
In this c a se the
b e ing under
i h
G m
G m
3
7
5
5
8
i
e
n
s
v
a
c
e
e
d
p robabl e
m
s
i
—
at )
l
.
A
A
00 0 00
.
t mi c
o
.
.
.
.
.
.
.
.
.
.
.
.
.
.
”
1
.
5 6 1 53 6
1 0 7 7 1 56
7 24 5 1 4
7 30515
1 1 854 12
7 23 2 3 0
7 4 70 42
.
.
f
Ag
c i
ra
.
880 7 4
4 4 3 88
0 0 681
0 4 83 3
1922 5
4 9 9 795
5 1 6 26 2
I
th e R a ti o A g : K C l
xgi u
Kg l
g
a
a
“
f
iii i gi u
e
ra
19
21
24
27
o
e rror is even S o m e w hat l ess than before
I
I
D S C US S O N O F F NAL RES U LTS
,
.
Thu s t w o resul ts ha v e been obt a ined gi v ing f o r the ato m ic w eight o f
potas s iu m the va lu e
by re f e rence to a rgentic chlo ride and the
v a lu e
by reference to pu re m etallic silve r The close agree m ent
o f the s e result s i s an i m portant e v iden c e o f th e ir v erity a nd a striking
confir m ation o f t h e n e w ato m i c w e ight of c hlorine f ound by R ich a rd s and
We ll s The ato m i c w e ight o f chlorine i s v ery s i m ply cal culated f rom the
r e s ult s o f the t w o se ries a bo v e a s f ol lo w s : C l
v ery ne a r the m o s t l ikely va lue
S uch di ff erenc e as e xists i s probably d u
e to the S l ight re m aining t race
o f o cclu s ion o f f oreign sa lts by the argentic chlorid e In t h e pres e nt c a se
this s ou r c e o f erro r wa s el i m inated mo re suc c es s f ully th a n e v er be f or e
h e nc e th e a gr e e m e nt b e t w een the t w o v a l ues o f the ato m ic w eight o f
pot ass iu m was clo s e r th a n u sual
,
,
.
,
.
:
,
.
,
.
I
D SC
US S ION
OF
FI NAL
RES
ULTS
23
.
be noted th a t the di ff e rence be t w een the new v al ue a nd th e
O l d value o f S t a s i s so m e w hat l e s s than in the case o f so diu m
S tas s
results w ith potas si c chl ori de led h i m to the valu e
about
higher than th e new r e sul t w hile w ith so dic chloride the di f fe rence w as
A la rge part o f th is di f fe rence in each case i s du e to S tas s erro r
in the ato m i c w eight o f chlo rine ; co rrected f o r this erro r the di ff e rences
beco m e
and
re s pectively The di ff e rences a re to be re ferre d
to the sa m e cau se s in thi s cas e a s in the othe rs
na m e ly to S tas s i n com
pl e t e kno w ledge conce rning solutions o f argentic chloride to his p ractice
o f dropping sol id salt into the precipitating solution a nd to the p re s ence
in hi s p reparations o f trace s o f i m pu rity t a k e n f ro m containing vess els
In th e ca s e o f potassiu m one o r m o re o f these errors mu st h av e been
les s than in the case o f sodium
Th e re sults o f R i chards and A rchibal d although ve ry fe w in nu m ber
a nd not intended to figu re in a dis cu s sion O f thi s kind were somewh a t
bette r — p robably becau se soli d salt was neve r u sed di rectly in p recipita
tion As s u m ing the p re sent research to yiel d the true v alu e thei r e rrors
i n the two se ri es w e re respecti v ely
and
The resul t o f
Archibal d al one fo r th e ratio o f S ilve r to potassiu m oh l o r i d e was about
th e sa m e a m ount
di f ferent fro m the p resent v alu e ; but his resu lt
fo r the othe r ratio was l es s satis factory ha v ing an error o f
e v en
greate r than S tas s Thes e d i f ferences a re not su rp rising b e cause le ss
w a s kno w n at that ti m e than at present conce rning the behavio r o f
a rgenti c chlo ride in solution
Although the pre sent pape r p re sents st rong evidence that the ato m ic
w eight o f potassiu m i s reall y as lo w as
m ore re m ains to be done
It w oul d have been de s i rabl e to ha v e u se d al so some othe r w holly di ff e rent
method o f p repa ring pot a ss ic chloride and mo reo v e r to have evaporated
la rge sa m ples o f the s a lt in nit rogen in o rde r to di sco v e r a po s sibl e non
vol a til e residu e I t is v ery doubt f ul i f these additional experi m ents w oul d
have alte re d the present result especi a lly cons ide ring t h e p recautions
taken in the w ork and the re s ult o f the following res earch ; bu t never
th e l e s s it i s planned to pu rsu e the se m att e rs fu rthe r
E ven when every concei v able p recaution i s taken a S ingle salt is not
an adequate basis fo r t h e certain deci s ion o f an ato m i c w eight F o r
thi s rea s on a pa ral l el investigation on potassi c bromi de w as s i m ultaneously
in p rogress at the C hem ical L abo rato ry o f H a rva rd C olleg e The next
co mm unication desc ribing th is othe r r e s ear c h mu st be c onsidered in
connection with th e w o rk w hi c h has j u s t b e en de s cribed A S w ill be seen
excellent confi rmation o f t h e p r e s ent w ork i s a ff orded by the wo rk w ith
the bro m ide
It
m ay
’
.
,
’
,
.
’
,
,
,
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.
,
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,
,
,
i
,
’
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,
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,
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,
,
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.
,
24
TH E A N A
LY S I S
OF
P O T A S S I C C H L O R I DE
.
S U MMAR"
.
This in v estigation conc e rning t h e quantit a ti v e c o m position o f pot a ss ic
chloride rese m bled in m a ny r e spe cts the recent in v e stigation o f R icha rds
and We lls on sodiu m
In s e v e r a l det a il s ho w e v e r i m pro v e m ents w er e introdu c ed w hich
e f f ected a conside rable sa v ing o f ti m e a nd a pe r ce ptible gain in accu r a cy
The precautions necessary f o r the a c cu r a te u se o f th e G ooch —
M u n roe
perforated crucibl e we re a s certain e d ; its e m ploy m e nt w a s f ound to be
ad va ntageou s
P latinum weighing bottl es with conic a l ground platinu m stoppers were
u sed instead o f bo a t s and glas s tubes f o r w eighing the pot a s s iu m salt
O cclu s ion o f argentic nitrate by th e p recipitated chloride wa s di m in
i s h e d by all o w ing the l a tter to s tand f or a long ti m e in a solution contain
in g n e ither exces s o f sil v er no r e xces s of sol uble chlori de a nd by adding
mo re a rgentic nitrate only a f ter th e p recipitate had as su m e d a fa irly pe r
m a n e nt condition o f aggreg a tion
The nephelo m et ri c esti m a tion o f s m a ll a m ounts o f s u s pended a rgenti c
chlo ride w as increased in accu ra cy by redis sol v ing in a mm onia both o f the
opalescent p recipitates to be compared and r e p r e ci pi ta t i n g in o rder to
equalize the conditions
As fin a l results th e outcome o f t w el v e experi m ents
parts o f
sil v er we re fou nd to corr e spond to
parts o f potass ic chloride and
p a rts o f argentic c hlorid e w e re f ound to co rr e spon d to
o f this sal t
Th e corre s ponding v alues for the ato m ic w eight o f pot ass ium ( i f s ilve r
i s assu m ed to be
and chlorine
are
and
in
unusually close agree m ent
.
,
,
.
.
-
.
,
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,
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,
,
,
.
.
A R EV I S I O N
O F TH E
A TO M I C
WE I G H T
P O TA S S I U M
or
TH E A NA L "SIS O F P OTAS SI C BRO MIDE
.
.
I NTRO DU CTI O N
.
The foregoing quantitati v e stu dy o f potassi c chloride by D r Arthu r
S taehl e r and one o f the p resent autho rs a f fo rds strong e v idence that
the ato m ic w eight o f pota s sium is abou t
sl ightly lower than the
v alu e ba s ed upon the wo rk o f S tas The authors fully appreciated ho w
eve r that the investigation o f a s ingle compound is not enough to
establ ish a chemi cal const a nt so i m po rtant as this and acco rdingly the
present in v estigation was p ros ecuted s imultaneou sly It w as expected
that the two investi gations m ight e ithe r support one anothe r o r el s e b y
a f fo rding inco m patibl e re s ul t s lead to the di s cove ry o f a constant error in
one or th e other and thu s pave the way for fu rthe r advance in kno w l e dge
A s will be seen the work on the chl oride w as sati s f a c torily confirm ed by
th e wo rk on the b romi de
I n the p resent cas e the care f ul s tu dy o f potas s ic bromide w as p a r t i cu
l a r l y neces s a ry becau se the re al ready exist t w o conco rdant se ries of
expe riment s upon this sub s tanc e pe rformed by the O l d m aste rs Marignac
and S tas p ointin g to a valu e in the neighbo rhood o f
in s tead o f the
be fo re —
mentione d ne w val u e
In thi s case the highe r v alu e f o r
potass ium is not diminished as in the case o f the chlori de by an additive
co rrection in the atomi c w eight o f the h a l ogen because B axte r has
sho w n S ta s s esti m ate f o r bro m ine to ha v e been nearly co rrect
H ence
th e dis cr e pan c y re m ain s one too se riou s to b e tolerated
The ca re ful stu dy o f thi s w o rk o f S tas and Marign a c a ff o rds coh v i n ci n g
e v idence that the potassic bromide u se d by them fo r analy s i s w a s not
su f fici e ntly pu re for the purpo se S tas a dm itted that some o f h is p repar a
tions w e re not e v en w holly solubl e in w ate r and hi s m ethod o f procedu re
was su ch that so m e o f them p robabl y contained platinum and hydroxide
B ecau se S pe cu l a tions o f this kind c oncerning w ork so long past a re o f
b ut l ittle v alue it w as clearly necessary to repeat thi s w ork w ith modern
care ; and the following pages recount the det a il s o f the repetition
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1
A bri ef
ul a t i o n s
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c
1 90 6 ;
P
hil
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re
”
J ur
o
S oc
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,
n
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vi
of
ew
Am
p
.
4 3 , 1 16
.
S
t as s
an d
M a r i gn a c s
’
ax t s
k s
B
er
i
wor
em
S oc , 2 8, 1 3 22
47
Ch
’
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’
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wo
to
rk
be
a k s R al
f u di P
ad 4 2 2 0 1
S e a l s o R i h a r ds T a s A m
m ay b e
o
n
n
e
f u d
o
n
r oc
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in Cl r
Am A c
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c
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e
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ec
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7
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28
TH E A N A
LY S I S
PO T A S S I C
OF
B RO
M I DE
.
In co mm on w ith others o f the sa m e type the inv e stigation easily resolves
itsel f into s eve ral sections and will be discu s s ed under the f ol lowing
heads : The pr e par a tion o f m aterial s ; the drying a nd w eighing o f po ta s
sic b ro m id e ; t h e dete rm in a tion o f the r a tio o f a rgentic to pot as sic bro
m id e ; the det e r m ination o f the r a tio o f sil v er to pota ss i c bro m ide ; and
the discu s sion o f the results O f the l a bor a tory tasks the p r e p a r a tion
o f the m a teri a l s w as by f a r th e most laboriou s and pu zzl ing w hil e the
analyti cal wo r k w as co m parati v ely S imple
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I
MATERIAL S
THE P RE PARAT O N O F
TH E SO
U RC E
O F TH E
POTA S S I U M
.
.
task o f p reparing pu re potassic b rom ide s i m ple a s it m a y appear
i s by no means a n easy one In vie w o f ou r expe rience it seems probable
that neith e r M arignac nor S tas eve r prepa red sampl es pu re enough to
co rrespond with the othe r precaution s w hich th e y took A s in th e case
1
o f sodic b ro m i de the s a lt itsel f wh e n on c e m a de c a n not b e e f fecti v ely
pu rifi e d In this re s pect it di f f ers w idely from the chloride We f ound
a fte r due trial that t h e potas s iu m and bromine m u st b e pu rifi e d sepa
r a t e l y in su ch f or m s as to intro duce no f oreign matte r
Accordingly
th e t w o substance s al ready adequately pu rified wer e cau sed a f ter w ards
to yiel d potassic bromide ; and this salt when recrystall ized gave the final
substance for analys is The pu rification o f the potas sium material s w ill
be discu s s ed first
It w as nece s sary to provide potass iu m mat e rial w hich s houl d be free
fro m the su spicion o f introducing any i m pu rity w ith the met a l desi red
either basi c o r acid P otassic nitrate w hich had se rved so well in the case
o f the chloride w as not suitabl e fo r the present pu rpose becau se the
d e struction o f the nitri c aci d in v ol v es too great a sacrifice of laboriously
prepar e d hydrobro m i c acid A fte r due conside ration potassi c oxalate
w a s tentativel y chosen It was nece s sary to p rove that this sal t can be
e as ily a nd cert a inly pu rified by recrystall ization and especial ly to S how
that the o ther alkal i m et a l s can thu s be separated The following tests
acco m pl ished this p roo f
A satu r a ted solution of potassic oxalate containing a pu rposely a dded
ad m i x tu re o f 1 0 per cent o f sodic ox a l a te w as c ryst a llized and th e crystals
dr a ined centri fugally By the flame te s t a pronounced di ff e rence was
notic e abl e between th e amount o f sodium present in t h e mothe r liquor
and th a t in the c ry s tal s A se cond recrystallization and whi rling was
still more s a tis f actory ; the c ry s tals g a ve no sodiu m test to the eye while
Th e
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h a ds
Ri c
3 48
r
an d
We l l s
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P ro c
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Am
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Acad
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4 1 , 43 5
Z e i t p h ys C h e m
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56,
TH E
P RE P A RA T I O N
OF
M AT E RI AL S
29
.
the mothe r l iquors gave a distinct yellow This indicates that sodium
h a s a decided tendency into th e mothe r l iquors and hence can b e sepa
rated by fractional c rystallization
Again 1 pe r cent o f l ithium salt was added to p otassic oxalate with
si m ila r ou tco m e R u bidium an d c aesiu m w ere tested like w ise A sat
ura te d solution o f potassic oxalate and a salt o f each o f these metal s w a s
m ade o f su ch strength that the rubidiu m o r c aes ium coul d eas ily be found
b y m e a n s o f the spectroscope
E ach solution w a s e v aporated until satu
rated and cooled ; and th e crystals were whirled The mothe r l iquor gave
a test for th e impu rity the c ryst a l s g a ve none
N0 othe r oxalate s w e re seriou sly to be f eare d becau se the insoluble ones
woul d ap p ear at once and demand filtration and solubl e doubl e ox a lat e s
coul d hardly be isomorphou s and w oul d the re fore tend into the mothe r
l i q uo rs Traces o f cal ci c oxalate in fact appeared in the fo rme r fashion
and traces o f i ron in th e latte r
In v iew o f these satis factory resu lt s it w as e v idently only necessary
to c ry stal lize the potas sic oxalate o f ten enough to make the s eparation
com p lete ; and since p otass i c oxalate has a fairly con v enient change in
solubil ity w ith the tem p e ratu re the yiel d after a consi derabl e number o f
c rystall izations i s good e s pec ial ly i f p ain s are taken to carry out the p ro
ce s s syste m atical ly
Two ve ry pu re sa m pl es o f oxalate we re made from two di ff e rent sou rces
As one sou rce o f mate rial a co mm e rcial sam p l e p repared by M e rck wa s
”
“
u sed It had b een la b eled P otassium oxalate neutral highest p u rity
and contained a s a matte r o f fact only the traces o f cal cium and i ron
al ready re f erred to but no lead o r othe r di scove ra b l e impu rity A large
q uantity o f a solution o f this salt w as filte red hot into a platinu m dish
where it was five ti m e s s y s te m atical ly rec rystall ized the c rystal s b eing
centri fugally whi rl ed each time
C a re ful s crutiny in the spe ctroscope reveal ed in the produ ct no othe r
s p ectro sco p ic line s than thos e o f potas sium and ca re ful qual itative tests
proved the a b sence o f lead and i ron The sal t dissolved without a t race
o f res idu e i n wate r and w a s qu ite p u re enough to se rve a s a starting
“
p oint fo r fu rthe r ope rations to be des cribed under the heading P otassi c
”
b romide
A second sampl e o f potassic m aterial w a s o b tained fro m M erck in the
“
fo rm o f th e hydroxid e being marke d P otass iu m H ydrate C hem i cal ly
P u re R eagent ; C on f orms to the standa rds o f D r K rauch
It w a s in
fact ve ry pu re giving a p erfe ctly cl ear solution both b e fore and a fter
neut ralizatio n It w a s neutralized w ith a s p ecimen o f oxal i c aci d which
had been ca r e f ul l y pur i fi e d by Mr G E B eh r j r for othe r wo rk This
acid contained no halogen s and l e ft no residu e on volatil ization in plati
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30
TH E A N A
LY S I S
PO TA S S I C
OF
B RO
M I DE
.
num S lightly mo re than the equival ent quantity o f aci d w as added and
the oxalat e obtained w a s there f ore slightly acid A S w ill be sho w n the
a cidity wa s l a t e r t h e cau se o f m uch inconvenience and had better ha v e
b e en av oi d e d The o xa l a t e w a s f ou r ti m e s systematical ly recrystallized in
platinu m w ith centri f ugal draining each ti m e The final produ ct l ike the
p re v iou s o n e ga v e no tests fo r i m pu riti es except a S light excess o f acid ;
it was u sed as the sou rce o f pota s sium fo r one preparation of potass ium
bro m ide
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B RO
MINE
.
Although the methods pre v iously used at H ar v ard ha d a f forded a
1
s a tis factory yiel d o f v e ry pu re b ro m ine it was desired to add to the
kno w l edge on the su b j ect by testing another method Through the gener
L ou is M i ssou ri and
o s i ty o f the M a l l i n ck r o d t C hemical Works o f S t
al so o f the D ow C h e mic a l Works o f M idland M ichigan a large quantit y
o f potas si c bro m ate wa s pl a ced at ou r di s posal R epeated c ryst a llization
v e ry kindly carried out for u s on a large sc a l e by these firm s had been
th e method u sed in its p u rification
This m aterial w hich se rve d as ou r starting point was al ready v e r v
pu re a fa ct wh ich was indicated by th ree syntheses o f argentic bromide
f ro m pu rest s ilver and potassic bro m ide obtained by decom p os ing the
Ma l l i n ck r o d t b romate Th e se synthe s es ca rried out with all necessary
p recautions ga v e respecti v ely
as th e percentage o f
Accord ing to B axte r the true amount is
S ilver in argentic b romide
The S l ight di ff erence indicates a trace o f iodine rather than
chlorine ; but this impu rity can b e easily expelled wh il e chlo rine i s fa r
more t roubl esome
It having b een demonstrated that recrystall ization i s an e ff ective means
o f pu ri f ying the s a lt f ro m chlorate and chloride a large quantity o f
potas sic bromate w a s th ree ti m e s recrystall ized i n porcelain the c rystals
being centri fugally whi rl ed each time and al l mother l iquo rs disca rded
Th is gave an e x ceedingly pu re b ro m ate mu ch p u re r than S tas coul d have
3
obtained because th e centri fu gal draining makes s o great a di ff erence
"
in the rate o f pu rification
A l a rge quantity o f the salt w a s decompose d into the b romide in a
platinum dish by the heat of an al cohol l a mp The p otass ic b ro m ate in
deco m posing attacked the platinum and the mass of b romide was sl ightly
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S e e P r oc A m P i l S o c , 4 3 1 1 9
f or
B el iq e 4 3 II, 3 8
2B
e r,
Am C e m
o rn
S oc , 2 8 , 1 3 3 2
Am P i l S o c 4 3 1 1 9
1
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g u
ax t J u
h
U t rs u hu g
R i h a r ds J u
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3
4
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rn
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1 60
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Am
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Ch e m
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S oc
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,
27
,
1 04
r e f e r e n ce s
S ee
an d
also
S
t as
,
Mem Acad
h a rds
Ri c
.
,
Tran s
.
.
P R E P A RA T I O N
TH E
OF
M A T ERI A LS
31
.
b ro w nish in colo r but this cau sed no inconvenience in the p res ent case
as the b romine was to b e su b se q u ently distille d I n o rder to li b erate the
halogen th e bromide w as t reate d in strong so l u tion w ith l ess than the
cal culated quantity of b romate and an exces s of p u re sul phu ri c acid The
a c id w a s added drop by d rop to the mixed solution o f salts in an appa ratus
m ade enti rely o f Jena gl ass which w as kept su rrounded by ice wate r
The bromine which v olatilize d on account o f the heat o f the reaction was
caught in a condense r under w ate r ; to thi s w a s added the re m ainin g
bro m ine which had been sepa rated from the su p ernatant solution b y
m eans o f a separating f unnel
Th e b ro m ine thu s obtained wa s twice distill ed b y steam heat into wate r
in a Jena glass condenser packed in i ce It w a s ke p t in a wel l seasoned
bottle with double ground —glas s sto p p ers
The produ ct was certainly free from non vo l atil e mater i als and coul d
have contained only iodine and perhaps a trace o f sulphu ri c acid a s
impu rity It w ill b e seen that these w e re el i m inated in the subsequ ent
wo rk Thi s was th e only sam p l e o f b romine p repared ; it was us ed in all
the p repa rations o f b romide a s the q uantitative results indicated that
it was very pu re
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P OT A S S I C
B RO
M I DE
.
Th e p roblem o f o b taining potas sic b romide from the oxalate and b ro
mine had been care fully cons idere d b e fo re these su b stances had b een
p r e pa red Only t w o methods reco mm ende d themselves f o r th e pres ent
pu rpose although the b romi de can be o b tained from these two mate rial s
by a v a riety o f reactions w hich w oul d ordinarily b e acce p t a bl e H ere
ho w eve r s impl icity completeness and theo retical co rre ctnes s mu st all be
fulfill ed ; that th e methods adopte d really possess ed th ese advantages in
thei r f a vor mu s t b e admitted after ca re ful p e ru sal o f the following d e s cr i p
tion o f the detail s
In some p rel imina ry expe riments it was S ho w n that by adding an exces s
o f b rom ine to the oxalate and evapo rating o ff the exce s s a v e ry p u re
b romide qu ite free from oxalate is o b taine d Acco rdingly a quantity of
t h e fi rst sa m pl e o f fi v e ti m e s crystal lize d potas si c oxalate w as t reated with
an excess o f b romine the bromine being added in small quantities from a
d ropping funnel The solution w as h e l d in a quartz di sh whi ch wa s
care f ully hoode d to p revent entrance o f du st When the a ction had
ceased the solution w a s heated on a steam b ath until any traces o f iodine
and al l excess o f bromine ha d b een ex p ell ed Th e solution was fou nd
to b e enti r e ly free from oxalic acid upon testing with ca l ci c n i trate in a
so l ution faintly aci d wi th nitri c acid Although it w as w hol ly colorl es s
w hile in th e qua rtz dish a fter being concentrated in platinum it devel oped
a v e r v faint yello w tinge U p on recrystall izing three times thi s colo r wa s
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TH E
ANA
LY S I S
POT A S S I C
OF
B RO
M I DE
.
finally concentrated i n the extreme mother liquor and was found to b e
du e to a trace o f platinum ; no i ron w a s p res ent E ven th e first crystal s
were p e r f e c tly w hit e the second and third mothe r l iquors al s o showed
no t race o f colo r and only the first of the moth er l iquors gave a test
fo r platinum
The m aterial thu s p repared a f te r being three times recrystallized in
pl a tinu m with centri fugal draining w as call ed sam p l e I and served for
analyses 1 to 1 1
The second sampl e o f p otassic bro m ide w a s p repared from the second
sampl e o f fou r ti m es recrystallized potassic oxalate Th e method wa s the
sa m e a s with the previou s sampl e An excess o f b romine was added t o
the ox a late in qu a rtz ; w hen action ceased the bro m ine w as d riven O ff by
heating on a s team bath H oweve r on testing for oxalate a perceptibl e
quantity w a s f ound still u ndecom p osed Th is was unexpected in view o f
the fact that the first preparation o f b romide had given no troubl e in thi s
respect The di f ficulty w a s traced to the presence o f a small percent a ge
o f a c id salt in the ox a late ; the p re s ence o f acid has an inhibito ry e f fect on
the reaction o f bromine on the oxal ate ion O bviou sly the si m pl est
remedy woul d have been to add pu re potas si c hydroxide ; but this was not
added becau se at that moment th ere wa s none at hand Moreo v er
b ecau se the reaction was being perfo rmed in quartz i t was thought best
not to u se a cau stic alkal i fo r f ear that the di sh might be S l ightly attacked
The addition o f a small amou nt o f very pu re recrystall ized bromate to
thi s slightly acid solution ser v e d b e tte r becau se its u se w as unattend e d
with dange r Its e m ployment w as enti rely e f fecti v e ; th e ionized hydrogen
was re m oved a n d a fter adding more bromine and heating a solution o f
bro m ide w a s obtained w hich contained no t race o f oxalate
This speci m en w as recrystalliz ed entirely in quartz in o rder to pre v ent
a r e cu rren ce o f the troubl e expe rienced with sa m pl e I as well as to see
i f the variatio n o f conditions a ff ected the atomi c weight Two cr y s t a l l i
z a ti o n s were m ade with centri fu gal draining
and every precaution ; an d
ther e w a s obt a ined finally a v ery pu r e colorl ess p rodu ct w ith w hi ch w ere
m ade t w o analyses No s 1 2 and 1 3
That a u ni form ly pu re material had
been made is shown by the close agreement of these two analyses with
the mean of all
A s a fu rther p recaution against accidental e rror it was thought best
to develop a method es sentially di ff erent fro m that j u st discu ssed and
to p repa re therewith a third speci m en o f bromide In brie f thi s method
consisted in the separate preparation o f pu re a mm onic bro m ide and
pot a s s ic hydroxide and the p roduction o f pot a ssic bro m ide by th e e v a po r
ation o f the m ixed solu tions o f these substances Thu s can be obt a ined
a salt contaminated only with exces s o f v olatil e a m moni c bromide
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TH E A N A
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PO T A S S I C
B RO
M I DE
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su r ro unded it in the tu be so that no certain quantitati v e evi dence coul d
be obtained T w o m i nute black spots were visible in th e boat ; no th i n g
els e coul d be seen upon v e ry care f ul sc r uti ny I f th ere w e re a n y silica
p r e s e n t the a m oun t m u st ha v e be e n too small to ha v e h a d an y app reciabl e
T ime and materi al w e re lacking
i n fl uence on th e fi nal a tomic weights
hence t h e expe ri m ent w a s not repeated
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S
IL VE R
.
The essential detail s o f th e preparati on o f pu re s il v er a s develo p ed by
R ichards and \Vell s w e re follo w ed in detail and the reader is re ferred
to t h e i r paper as w ell a s to the p rece ding paper o f R ichards and S taehle r
for the pa rti cular s T w o samples of sil v er w ere made ; the y w ere found
to b e i dentical in quan t itati v e beha v i or
The sou rce o f th e mate ri al u s ed f or the fi rst preparati on w a s the pu re
p recipi t ate d argenti c chlori de rem aining from the w o rk of R ich a rds and
m
It w as reduce d to m etalli c s il v er w i th in v e r t su ga r in
\V e ll s on s odi u
a strong solution o f so di c hy droxi de The sil v e r thus obta ined w as
w ashed f ree from soluble matt e r and di ssol v ed i n nitri c aci d ; the argenti c
ni tra t e a f t er c rystalliz ation and w hi rl i ng was redu ced w ith amm onic
fo rmate yiel ding a b eau ti ful c rystal l ine mass o f m etal
Thi s pu re s il v er a fte r v er y thorough wa s h i ng w as fu sed on l im e by
means of a bla s t lam p w ho s e tip had been c a re fully cl eaned The butt ons
w hich w e re thus ob t a ined w ere cool e d in the redu cing fl am e washed free
fro m l ime s c r ubbed w i t h cl eaned s ea sand etched with strong ni tri c acid
and w ashed w i t h th e p u rest water to se rve as anodes in th e electrol y ti c
pu r ifi cation w hich w as th e next step The el ectrol y sis w a s carri ed on
a s a l read y d e scribed in pre v iou s si m ilar H a rvard researches and e v e ry
step o f th e su b sequ ent w ork may be foun d in deta il in the p receding papers
on s odic and po t as si c chlori de
The m etal w a s finall y f u s ed as u sual on
a boat o f th e pur e s t l i me in an atmos p here o f hydrogen un der a tens ion o f
5 0 mm
The larger piece s a fter etching w ith nitri c acid w e re cut into
s m all e r ones o f con v enient siz e w i th a C l ean col d chisel They w e re again
2
etched in orde r to di s sol v e al l traces o f iron sc rubbed w ith cl ean sand
w ashed w i t h a j et o f w ater and etch ed yet again w ith aci d p a y ing par
ti cu
l a r a ttenti on to the cut edges
F inally the p iece s w ere dried o v er an
al cohol l am p and kept in a desic cato r o v er po ta ssic hydroxide for us e
This s il v er w as u sed bo t h in most o f the titrations again s t pot a s s i c
bromi de and as the sou rce o f ar g entic ni trate u sed in the preci p itation o f
argen tic b romi de to be w eighed
,
,
,
,
,
.
.
.
.
.
,
,
,
.
-
,
-
,
,
,
,
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,
1
.
.
.
,
,
-
.
,
,
,
,
.
.
.
S e e P r oc A m A ca d
C e S oc 2 7 4 7 3
2 Ri c
r
a n d A rc i b l
C e m S oc , 2 8 , 1 3 2 9
1
hm
h a ds
h
.
,
.
.
.
.
,
3 8 4 50
Ri c r
,
h ad
,
,
h a ds
P r oc
.
and
S
d Ric
ae
e r,
t hl
Am e r Aca d
.
We l l s J o u r n
p r e ce d i n g p ap e r
450
B ax t e r J o u rn
an
.
,
3 8,
h a ds
r
and
'
,
.
Am
.
Am
.
.
,
.
P RE P A R ATI O N
TH E
M A T ERI A L S
or
35
.
A s econd sampl e o f sil v e r p re p a red from some w hat l es s p ure ini ti al
material w as put through a mo re el abora t e and exh au sti v e rou nd o f
p u rifi cation w hich nee d not be de ta il ed T he p repa ration i nclu d e d fi v e
c rys tal lizations a s nitrate and t w o su cces si v e p recipi tations a s meta l by
fo rm ate Thi s sil v e r w a s fu sed into buttons o f a size sui tabl e fo r i mm e
diate u se withou t cu tt ing They w e re cl eane d by etchi ng and w a s hin g
dried and p res e r ved free from i mpu ri ty as u sual and w ere u sed in anal y s es
and 9
N IT RI C A C I D
,
,
.
‘
.
.
,
,
N
'
.
p rel i m inar y w o rk o rdina ry
che m ically pu re ni tri c acid w as
distill ed once u s i ng a plat i num condenser a n d J e n a glas s recei v e r th e
fi rst thi rd o f th e aci d bei ng di scarded F o r t he fin al analyses thi s re di s
tilled p roduct al rea d y v e rv pu re w a s once aga in di still ed as be fore th e
fi rst th ird be i ng rej ected Thi s di s ti llate ga v e no test w i t h th e ne p he l
a fter d i lu ti on
o m e te r
W A T ER
F or
“
”
,
'
,
,
.
,
,
,
,
.
.
,
As u sual in su ch work al l the w ater u sed had b een ca re fully p u ri fi e d b y
doubl e di stillation once from a fai rly s trong solu ti on o f alkali n e po ta ss i c
pe rm anganate and t hen alone Th e di s t i l late w a s ca ught i n Je n a gl a ss
receivin g flasks w hi ch were pro v i ded w i t h special adapters to p re v en t
the acces s O f du st The fi rst an d la st fra cti ons w e re al w ay s rej ected onl y
th e mi ddl e p o r tion bein g u sed The co n necti on o f th e Jena glass bo i li n g
1
fla s k w ith the pu re ti n condense r w a s made w i t hout rubber o r cork
S u ch w ate r ga v e eve ry e yi d e n ce of su ff i cient p u ri ty as ha s b ee n frequen t l y
t
po m t e d o u
TH E L A B O R AT ORY
,
,
.
,
.
,
.
.
,
.
A ve r y essenti al precau ti on i n eve r y s ta ge o f th is w o r k w a s to e fl ectua ll v
exclu de hyd rochl o ri c acid Accordingl y all th e p reparati ons o f th e b ro
m i de w ere c a rri ed out in a p r i v ate l abo rato r y u se d es p eciall y and onl y
for t hi s w o rk and who l ly free from th e inte r ference ca u sed b y la r ge
cla s ses o r o ther research es G rea t ca re w as ta k en not to all o w an y
h y drochlo ri c aci d in th e room ; in deed not a dro p was u se d th ere du ri n g
th e entire resea rch
A s epa rate v enti lati n g fan p revented fum es from
o ther labo ra to ri es from i nter fering w i th th e wo rk
.
,
,
,
.
,
.
.
U T E N S ILS
.
A s u sual great ca re was ta k en to avoid th e u s e o f an v vess el s w hich
under th e gi v en conditions might be atta c k ed an d t hus po l lute the su b
stan ce i n hand Wh en glass an d po rcela i n w ere not ha r m ful a s i n th e
ea rl y stage s o f the p repa ra t ion o f s il v er such receptacl es were em p l oyed ;
bu t in the pu r i ficati on o f t h e subs tance fo r anal y si s p lati n u
m an d qua rtz
w e re al w a y s u sed
,
,
.
,
,
.
1
h a r ds
Ri c
,
P ro c Am
.
.
Acad
.
,
30
,
3 80
36
TH E A N A
LY S I S
or
P OT A S S I C
WEI G H I NG
THE DR"I NG A ND
B RO
M I DE
O F PO TASS
.
IC
I
BRO M DE
.
reasons al ready mentioned in the pape r on p otassi c chlor i de th e
salt unde r investigation must be fu sed b e f o re weigh ing U nfo rtunately
p otas si c bromide when fu sed in air in a platinum vessel atta cks the p lati
num to a considerabl e extent Although it i s sho w n l a ter th a t this a ction
does not s eriously a ff ect the weight o f silver needed to precipitate th e
b romine in the salt it wa s nevertheles s desira b l e to avoi d al l such i r r e gu
l a r i ti e s
N0 such action i s o b served when the fu sion takes p lace in an
atmos p here o f p u re dry nitro g en Accordin gly in al l work to be r e
counted the potass ic b romide w a s p rotected i n thi s way du ring its fu sion
i n a well seasoned p latinu m b oat and wa s fi nally b y means o f the H arvard
“
”
bottling a p paratu s S hut u p in a tight weighin g b ottl e in an atmos p he r e
of pu re dry a ir The detail s h ave already been adequately given in several
p laces es p ecially i n th e account o f the recent work on the atom i c weight
o f c aesium
The only di f ference in the present p rocedure w a s demanded
b y the high fu sin g p oint o f p otas sic b romide
on account o f this
a p orcelain ignition tu b e was su b stituted fo r one o f gla ss a s in the cas e
2
o f cal ci c chlor i de
E ven w i th all pos si b l e care howeve r the p latinum b oat w a s d i st i nctly
attacked almost always losin g in weight du ring the fu s i on I n two o f th e
cases — analyses 1 and 1 4 — where th e potassic b romide was fused f or
s om e time in th e b oat the corrosive action was very conside ra b l e causin g
l osse s o f weight o f
and
gram res p ectivel y One woul d b e di s
p osed to rej ect th ese dete rm i nat i ons entire l y exce p t for th e fact that the i r
F or
,
,
.
.
,
.
.
,
,
-
,
,
,
.
,
1
.
-
,
-
,
.
,
,
.
,
,
,
.
,
,
a
v e ra g e resu l t
KB r
,
is
As
the ave ra g e o f result s
al l namely
,
5
and
almost exactly identical w ith that o f
i n wh i ch th e b oat
6,
wa s
s carce l y a ttac k ed
at
Instead o f b e i n g rej ected thes e result s
,
,
a re there fore reta i ned and u sed a s ev i dence that even a cons i dera bl e
amount o f dis solved platinum h a s no perceptibl e e ff ect on the weight o f
S ilver p recipitated by the sal t
In a maj ority o f the othe r cases the change
in w eight o f the boat du ring the fusion was l ess than
gram The
ave rage l oss in analyses 1 0 1 1 1 2 and 1 6 i n wh ich the argenti c b romide
w a s weighed was l es s than
gram ; hence even i f plat i num had
been p resent in the p otas sic b romide in a state o f fin e division i t coul d not
have exerted any e ssential e ff ect u p on the resul t o f this series o f analyses
.
,
.
,
,
,
,
,
.
1
R i ch
3 4 , 3 62
2 Ri
c
a r ds
an d
Arch i ba l d
,
.
h a rds J u r Am r Ch em
,
o
n
.
e
.
Am e r Acad
P r oc
.
.
.
,
S oc , 2 4 , 3 7 4
.
3 8, 4 5 1
Ze i t
.
an o rg
.
Ch em
.
,
YI N G
TH E DR
WE I G H I N G
A ND
OF
PO T AS S I C
B RO
M I DE
37
.
matter o f fact th e p otas s i c b romide a l ways gave a p erfectly c l e a r
a q ueou s solu tion exce p t once namely in analys i s 1 4
In this case seve ral
s mall fla k es o f p l atinum were noti ced i n the sa l t bo th b e fore and a fte r th e
s al t w a s diss olve d in wate r
Th e so l utions we re a l ways p er fectly neutral to p heno l phthalei n a fact
w h i ch i s ade q uate p roo f o f the retent i on o f a ll th e b rom i ne du rin g fu s i on
a n d a l so of th e a b sence o f oxa l ate from the p otassi c b rom i de c rystals
The thi rd sampl e of p otassi c b rom i de had conta i ne d ammoni c b rom i de
wh i ch w a s ex p e l led du rin g th e fus i on D u rin g the ex p ul sion o f this sa l t
t h e b oat w a s p laced near the exit end o f the p o rcelain tu b e and th e r e
g ra dually heated to redness in a cu rrent o f nitro g en D u r i n g th e entir e
o p eration the mi ddle p o rtion o f th e p o rce l ain tu b e was k ept red hot in
o rde r to p revent b ac k ward di ff u sion o f the ammoni c b rom i de
wh i ch b y
c ondensin g might late r cau s e a contamination o f the p otass i c b rom i de
A l l the ammoni c b rom i de havin g b een su bli med the b o a t was p u shed i nt o
the m iddl e o f th e tu b e and the p otassic b rom i de fused as des cri b ed a bov e
There b ein g a p ossi bi l i ty that even at the fu s i n g p oint o f p otassi c b rom i de
s ome ammon i c b romi de m i g ht stil l b e retained another p ortion o f th e sam e
th i rd sam p l e o f b rom i de w a s fused unde r a pp rox i mately the same cond i
t i ons a s in th e analys es
The solution o f the b rom i de thu s o b ta i ne d w a s
s u b m i tted to th e N es s l e r test b e i n g com p ared with a tu b e o f p u re wate r
c ontainin g the same amount o f reagent
No co l o r w a s v i s ib l e i n e i the r
tu b e hence no a pp recia b l e amount o f ammon i c b rom i de rema i ned to con
t am i n a te the p otass iu m s a lt
Th e sa l t thu s pre p a red fo r ana l ys i s was wei g hed i n i ts glas s sto pp e re d
weighin g b ottl e b y su b st i tut i on u sin g a s the su b stitutin g ta re a p rec i sely
s i mila r w e i ghing b ottl e S u ccessive wei g h i n g s o f the sam e S p ecimen were
Th e b alance and weights w ere s i m i la r to
a l way s p ract i ca ll y i dent i ca l
thos e u sed w ith sodic and p otas si c chlo rides and al l the p recautions we r e
the same At each we i gh i n g th e h e i ghts o f the b aromete r the tem p eratu re
o f th e b alance room and the hum idity a s indicate d b y a hygromete r were
recorded The density o f th e d i s p l ace d a i r coul d thu s b e determined fo r
each case The var i at i ons from the ave ra g e we re howeve r not enough to
a ff ect essent i a ll y any o f the resu l ts a s we i g h i n g s we re not made unde r
any a b no rm al atmos p h er i c cond i tions Th e weights w e re o f cou rse stand
a r d i z e d b y the u sual H arva rd metho d
The s p eci fi c g rav i ty o f p otass i c b rom i de must b e k nown to w i th in fiv e
nit i n o rde r to correct th e we i gh ings to the vacuu m
o n e hu nd redth s o f a u
1
Its dete r m i nat i on ha s b een unde rta k e n
s tandard w i th su ff i c i ent accu racy
with a var i ety o f metho ds w i th a var i ety o f results ran g i n g from
to
As
a
,
,
,
.
.
,
,
.
,
.
,
,
.
-
,
.
,
,
.
-
,
.
,
.
,
.
-
-
,
-
.
.
,
,
.
-
,
.
.
,
,
,
.
.
-
.
,
,
1
F o r th e
l i t e ra tu r e
h e Tab e l l e
i sc
n
L an d o l t u B Or n s t e i n ( Me y e rh o ff e r )
a n d C l a rk e C o n s t an t s of Na tu re ( p a r t
s ee
.
,
.
P h ys i k a l i s ch
Ma cm i ll a n
-
C h em
38
P RE P A RA TI O N
TH E
M A T E RI A L S
OF
.
The more recent resul ts all tend towards the highest value found
b y K r i ch m ey e r
This appeare d to be the most probable becaus e
the u sual e rro rs cause low results ; b ut a s thi s determination was mad e
with only a s ingle crystal and a s the salt weighed in the p resent research
had been fu sed it was thought be s t to investigate fu rthe r Acco rd
i n gl y a pu re sa m pl e o f potassi c b ro m id e w a s fu rther pu rified b y c ing
three times recrystall ized with centri fugal draining when it gave no flam e
2
test fo r sodium
This p roduct w a s f us ed in platinum and coar s ely
p ul v e rized ; its S p ecific gravity was dete rm ined in an O stwal d pycnomete r
modified fo r u s e with solids u sing toluol a s the flu id to b e dis p laced The
toluol had been redi s tilled and poss es sed a density
at
re fe rre d
to water at
grams o f potassi c b romide displaced
grams
of the toluol at
a resul t which indicates a density o f
Time was
l acking fo r a re p etition o f the experi m ent but th is p rel iminary result wa s
enough to S how that the fu se d sal t i s es sentially in the same state as th e
crystallized salt The di f f erence b etween the two values i s too smal l to
a ff ect the vacuum co rrection ; the average valu e
was us ed
,
1
,
,
,
.
,
,
.
,
.
,
,
.
.
I I
WEI GH I NG
I
THE PREC P TAT O N A ND
ARGENTI C
OF
I
BRO M DE
.
In orde r to determine the weight o f argenti c b romide o b taina b le from
the b rom ine in potassi c bromi de the latter sal t was precipitate d by a very
sl ight excess o f a rgentic nitrate both substances being dis solved in l arge
q uantities o f the p u rest wate r The m ethod di f fere d b ut slightly from
that which had b een u sed re cently i n s o many other cases o f the same
k i nd Th e argentic nitrate was p repared from a weighed amount o f
p u re s ilver but no attempt was made in this series to determine the exact
amount o f silve r requi red as it was desired not to compl icate the proc e s s
b e fo re weighing the a rgentic b romide C are was taken to have an exces s
b ut only a sl ight exces s The silver was dissolved in nitric acid with al l
the u sual pr ecautions and the preci p itation was carried out in orange red
li ght in the dark room devote d to accurate wor k o f this kind The po ta s
s i c b romide had b een dissolved out of th e b oat b y digestion in a large
platinum dish and been t rans ferred to a 2 liter gl ass stoppere d Jena
E rlenm eye r flas k with care ful rinsing and every precaution to p revent
any gain o r l oss A fter being w ell shaken the flask containing the S ilve r
b rom i de was allowed to stand until the mother l iquor had b ecome cl ear
The solution was filtered through a platinum G ooch Mu nroe crucibl e
and the precipitate was washed by decantation first with an extremely
dilute acid solution o f S ilver nitrate and finally with exceedingly dilute
,
,
.
.
,
,
,
.
.
-
,
-
.
-
-
,
,
,
.
.
-
,
,
,
h
K r i ch m e y e r , Z p h y s ik a l C e m , 2 1 , 8 1
2
5 e e K r i ch m e y e r s e p e r i e n ce l o c ci t
1
.
’
x
.
.
,
.
.
TH E
P RE C I P IT A TI O N
A ND
WE I G H I N G
G
OF AR E N
TI C
B RO
M I DE
39
.
nitric acid to p revent colloi dal solution
W ith th is latte r faintly acid
l i q uid the p reci p itate w a s t rans ferred to th e c ru ci b l e The silve r b romide
w a s drie d at l east twe l ve hou rs in the filterin g cru ci b l e at 1 3 0 in an elec
t ri c oven " and w eighed It w a s then fused in a po rcelain cru cible in a
fu rnace where it was e ff ect i vely p rotected from flam e gases i n o rde r to
determine the trace o f moistu re always retained The wash wate rs and
th e solution o b taine d on neutral iz i n g the ammoniaca l rinsin g s o f the flas k
gave no i ndication o f the p resence o f b romine on care ful testin g in th e
ne p he l omete r
In u sing th e G ooch Munroe cru ci b l e al l the p recautions pointe d ou t
i n the p recedin g p a p e r were care ful l y hee ded A p erfo rated p late was
always p lace d on top o f th e fria bl e s p on g e to p revent ru p tu re A fter each
dete rm ination any b romide clingin g to it w a s leached out with potassi c
cyan i de which w a s then washe d away with nitric ac i d and finally ve ry
thorou ghly w ith wate r Th e solvent act i on o f the cyanide occas i onal ly
l oo sened p ortions o f the s p ongy fi l m b ut there was no d iffi cu l ty in re p a i r
i ng the i nj u ry U p on dry i n g in th e e l ectri c oven the cruc ib l e was ready
fo r anothe r ana l ys i s
In addition to the los s o f wei g ht on fu s ion two oth e r ve ry smal l and
somewhat uncertain corrections we re a pp l ied to th e weight o f the a rgenti c
b romide b u t b ecau se they we re o f a b out th e same ma gn i tu de and o f
o pp osite S ign thei r e ff ect was p ractically ne gl igi b l e Thes e we re a cor
rection fo r p latinum corro de d from th e b oat du rin g th e fus i on o f p otass i c
b rom i de and a co rrect i on fo r ar g enti c b rom i de disso l ve d in th e wate r u sed
B ecaus e thes e correct i ons have not b een considere d in most
f o r wash in g
wor k of thi s k i nd a word a b out them may not b e am i ss
I n the seri e s under discus sion the average loss o f th e b oat i n each dete r
mination was l es s than
g ram All o f thi s trace o f p latinum may
have been p resent as invisibl e du st in the solution and thu s may have b een
wei gh ed w ith the argentic b rom ide o r all o f it may have b een i n a so l u b l e
form an d may have remained in solution B ecau se o f this uncertainty
a com p romi se w a s made and hal f o f the l os s of w e i ght o f th e b oat ( in the
mean
g ram ) wa s su b tracted from each weight o f argenti c b ro
mide As th e average total we ight o f a r g entic b romide wa s over 4 gram s
th is com p romi s e cou l d not have introdu ced an erro r a s g reat as 1 p art i n
i n e i the r di rection
2
According to S tas ar g enti c b romide i s wholly insolubl e in wate r b ut
l e n t fo rm it i s un q u estiona bl y
recent expe riments show that in the fl o ccu
8
solu b le to a s l ight extent
A s in the case o f the chlor i de its solu b i lity i s
.
.
°
.
,
,
-
.
.
-
,
.
.
,
,
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,
.
,
.
,
,
.
,
,
.
.
,
.
,
,
.
,
,
,
.
.
,
,
,
.
h a ds A m C h m J o u r 2 2 4 5
t as u vr s I 89
Z f ii ph ys k C h m 4 6 6 0 2
ph ys C h em 1 2 23 4 ( 1 893 ) a l so R i h a r ds P ro
Ri c r
2
S
Oe
3 B 6tt e r
g ,
1
e
,
.
,
,
,
r
.
.
e
.
,
,
n
.
,
,
e
i e,
.
.
i
.
,
Ko
,
c
,
c
.
Am
.
h l ra u s h
Acad
c
.
,
un d
3 0 , 3 85
Ro
s e Z ei t
,
.
40
TH E A N A
L YS I S
PO TA S S I C
OF
B RO
M I DE
.
greatly d i m i n i shed b y the addit i on o f an excess o f either p reci p i tant ; b ut
whethe r o r not any i s dissolved b y a very dilute acid solution o f argentic
nitrate such a s that u sed in washin g i t i s p ractically im p ossible to discove r
I t i s not unlikely however that a b ou t a s mu ch wa s dissolved b y this so l u
tion as b y the dilute hydrob ro m ic acid u sed by B axter in his admi rable
1
wo rk on the atom i c weight o f b romine ; and in th is solution it is easy to
find th e amount o f dissolve d su b stance B axte r found as a m atte r o f fact
in his last s even most exact syn the s es an a v erage o f
gram of
argentic b rom i de i n each o f the wash waters
a figu re which was adde d
to each o f ou r weights o f argentic b romide becau se the othe r ci rcumstance s
o f th e analys i s were S i mila r i n th e two cases
O n the average th i s cor
rect i on exactly e l iminates the other ; and exce p t for the sa k e o f com p lete
nes s they might b oth have b een whol l y ne gl ected
O f cou rse al l the weighings we re corrected to the vacuum standard b y
adding
gram to eve ry a pp a rent g ram o f argent i c b rom i de and
gram to every ap p arent gram o f potass ic b romide as calcul ated
from the fi gu res
and
for the dens i ties o f a rgenti c b ro
mide " p otass i c b romide and the b ra ss weights respectively A ll the
dete rm i nat i ons made are given in the ta bl e b elo w
.
,
,
,
,
.
-
,
,
.
,
.
,
,
.
,
.
Th e R a ti o
Ex
i
n
wc
i m i nt
mb e
i
a
i
.
o
'
gh
f A r g en ti c B r om i d e
f KB r
C o r e cte
i i i um
i
v
i
ci
G m
ra
of
.
s
n
A
r
d
“
in
v ac i
76
P a ts f K
f
lo
‘
f g
gj
g
gh
i ui
ri
ra
“
.
.
s
63
63
63
63
.
.
.
.
To t a l
1 7 4 1 99 7
1 1 0 395
.
an s
'
r
.
A
t m i c W e i gh t
‘
B fg g
gg
gs
o
of
a sl
o
o
.
.
.
Br
o
r
3 45 6 1 7
6 6 2 2 85
3 2620 6
4 0 7 889
2 1 90 2 7
4 1 970 5
2 0 67 23
B r omi d e
o ta s s i c
o
G m
.
to P
.
.
.
.
3 7 28
3 7 23
3 7 19
3 73 6
63 3 7 2 7
0 0003
.
.
.
39
39
39
39
.
.
.
.
114
1 13
1 12
1 15
39 1 135
0 0 004
.
.
The extreme deviation from the mean co rres p onds to an e rro r o f wei gh
i n g the potassi c b rom i de o f
gram a reasona b l e quanti t y The
”
“
p ro b able error i ndicates that the re i s b u t l ittl e chance that the atomic
we i ght o f p otass ium i s mu ch b elow
o r much a b ove
i f con
stant chemical e rrors we re su cces s fully exclu ded S tas found in a s in gl e
experi m ent the nu m be r
instead o f
W i th u nlimited time mo re dete r minat i ons might wel l have b een made
b ut th e agreement o f these fou r results i s s o good that fu rthe r re p etition
seemed to b e not very u r g ent
.
,
.
,
.
B
2B
3S
1
ax t r J o u r Ame r C h m S o c 2 8 1 3 22
ax t e r d H i e s Am r C h em J o u
31
t as U t e rs u chu g e ( Tra s Aron s t e i
e
n
,
an
,
n
.
e
.
n
e
,
n
n
.
.
.
.
n
.
,
,
rn
.
,
n
,
22 0
p ag
e
3 40
.
42
TH E A N A
LY S I S
P OT A S S I C
OF
B RO
M I DE
.
o f silve r we re ap p lied Most o f these ex p eriments we re made b e fo r e
those given in the p recedin g table a fact which may account for the
sl ightly l ess satis factory agre ement o f th e individual results B ecau se the
deviations coul d not be trace d to any definite cause o f distu rbance they
mu st b e ascribed to accident
.
,
.
,
.
Th e R a ti o
E p e i me n t
x
n
W e i gh t
i Wc
u mbe
r
.
P r o b a bl e
e r r or
W e i gh t f S i l ve
in v cu um
o
mm
u
“
n
G m
ra
f P o ta s s i c B r o m i d e
KB r
of
r
o
s
In
.
a
Th e
o
ffggfid f i
t
r
co
.
s
o
.
Ato 'l c
’
t0
p a ts A g
r
if
.
gt
0
B
w ff i gh t
0
f
8 55 mm
r
.
. .
ave g e
i s ca l c u l t e d f m th e ve g e
t h e a t m i c e i g h ts i n th e c l u m n a v e T h d if e e n ce i s c
1
to S i l v e r
ra
a
w
o
bo
ro
.
a
e
f
of
r
f m the ave a g e
u s e ve s li gh t
no t
ra
o
r
ro
ry
r
of
the i n d i v i du l
a
v lues
a
of
.
The p roba b l e error i s as small a s b e f o re b ecause o f the g reate r
num b er o f dete r minations ; and the mean deviation from the avera g e valu e
It will b e o b s erved that these results
i s only one in the last decimal p l ace
p oint to th e l imits
and
as th e extreme values b etween wh ich
the ato m i c weight o f p otassium m ust fall in es sential agreement with t h e
p reviou s results
Ma r i gn a c s s e v e n experi m ents on thi s ratio give values ranging from
to
whi l e S tas s fou r teen results ranged from
to
”
“
.
,
.
’
’
Obviou sly the results fu rn ish a means o f cal cu lating the atomi c weight
o f bromine when taken in connection with the foregoing series entirely
i ndependent o f any othe r work Thu s B r
a valu e almost i dentical with Baxter s valu e
Thi s
i s excellent proo f that the b romine u sed in the present research was pu re
and that the o cclu sion o f electrolytes b y argentic b rom i de was small
,
,
.
2
’
,
,
.
TH E A
WE I G H T
TO M I C
ATO MI C WEIG HT
TH E
PO T A S S I U M
OF
O F PO TAS S
43
.
I UM
.
Th e p recedin g p a p e r and th e p resent one to g eth e r yiel d fou r ratio s
determine d with mode rn p recision which togethe r fix the atomi c we i ght
o f p otassium as definitely as cou l d b e ex p ected The res p ective values are
a s fol low s :
,
”
.
F r o m th e
F ro m t h e
F r om t h e
F ro m t h e
ra t i o
ra t i o
ra t i o
ra t i o
a rge t i c t o p o t ass i c ch l o r i d e
m e t a ll i c s i l v e r t o p o t ass i c h l o r i d e
a rg e n t i c to p o t ass i c b rom i d e
m e t a ll i c s i l ve r t o p o t ass i c b rom i d e
of
n
of
c
of
of
Av e r age a t om i c
w ei g
ht
of
p t ass i u m i f
o
,
Ag :
10 7 93 0
.
.
K
:
39 1134
K
:
39 l l 45
K
:
K
:
39 1 143
K
:
3 9 1 13 9
.
.
.
.
Thes e figu res a re intere sting and S ignificant The maximum departu re
from the me a n i s only 1 pa rt in
and such di f fe rences as exist in the
fi g ures a re ex p l icab l e It i s l i k ely that the S l i ghtly lowe r valu e given b y
the first mem b e r o f each p ai r o f s eries was du e to a t race o f occl us ion o f
p otassi c nitrate b y each o f the p reci p itates
a ci rcum stance whi ch can not
be a b so l utely p revented There fore th e highe r value s ave ragin g
a re m o re p ro b abl e Th e d i ff erences a re howeve r who l ly negl igi b l e at
p resent
In this connection it i s interest i n g to note that C l arke in 1 89 7 from a
miscellaneou s coll ection o f p a rtly unce r tain results o b tained b y others
deci de d u p on the almost i dentica l valu e
although at th e sa m e tim e
from sim ila r re sul ts he o b taine d values mu ch too l ow fo r ch l o rine and
iodine somewhat too l ow for b romine an d mu ch too high for sod i um
The ve ry c l ose mu tua l agreement o f the new results o b tained from two
di ff e rent com p ounds i s a satis facto r y ve rification o f the relative valu es
2
y i el ded b y the recent wo r k on the atomi c we i ghts of ch l orine and b romine
The va l u e o f ch l o rine found from the wo rk on p otas sium chlo ride w a s
and that o f b romine from the p resent wo rk i s
The rati o
o f chlo rine to b rom i ne is thu s found to b e
whe reas th e ratio com
te d from the wo rk o f R ich ards and W ell s and of B axte r i s
pu
Against su ch an accumulation o f concordant data a s that j u st presented
th e ol der figu res can have no im p ortant weight W hateve r may have b een
th e cau se o f the i rre gu l arity and i nterna l i ncons i stency o f S tas s results
w ith p otassic ch l oride and b rom i de th ere s eem s to b e l ittl e reason to
dou b t that the outcom e o f the p res ent i nvesti gat i on
really r epr e
sents the atomi c weigh t o f p otas s i um
It i s needles s to p oint out that this change in th e atomi c weight o f pota s
sium w ill a ff ect m any othe r atomi c weights
.
.
.
,
.
,
,
.
,
,
,
,
.
,
.
"
,
.
’
,
,
.
.
a l cu l a t i o s p 5 7
R i h a r ds a d W e ll s l oc
B ax t e r l oc ci t
1
2
Re c
n
n
c
,
.
,
.
.
,
.
.
ci t
.
h a rds
Ri c
,
Tra n s
.
Am e r
.
P h i l S oc 4 3
.
.
,
,
1 16
( 1 90 4 )
44
TH E A N A
L YS I S
S
OF
P OT A S S I C
B RO
M I DE
.
UMMAR"
.
Th i s i nvesti gation u p on the atom i c weight o f p otas sium p resents amon g
the follow i n g additions to the k now l e d ge o f th e
o the r cons i de rations
s ubj ect
( 1 ) The p ro bl em o f p re p arin g p u re p otas sic b ro m i d e w a s so l ved i n
t wo ways
( 2 ) An unusua l ly sat i s factory metho d for p re p ar i n g p u re p otass i um
hydroxide wa s develo p ed This method i s a pp lica b l e to othe r alkalies and
w i l l b e des cr ib ed e l sewhe re i n g reater detail
nd
s
m
a
The
rat
i
o
o
f
s
ilver
to
p
otassic
b
rom
i
d
redeter
i
ned
3
e
a
w
( )
found to b e
The atomic weight o f p otass i um w a s thu s
found to be
i f s ilver i s
and b rom ine
( 4 ) The ratio o f a rg entic b romide to p otass i c b romide w a s found to b e
This determination yielded an essentially equal va l ue
,
,
‘
.
.
,
.
,
,
K
( 5 ) These valu es con fi rm in a str i k in g manner the s i mu l taneou sly
e xecuted wor k u p on p otas sic chlo ride
and unite w i th them i n show in g
that the atom i c wei ght o f p otass i um 1 5
( 6 ) B y thu s agreein g these fou r va l ues su pp o r t th e new va l u e f or th e
a tomic weight o f chlo rine in rel ation to s ilve r and b romine
,
,
.
III
TH E Q U ANTI TATIV E S "NTH ES I S
A ND TH E
A TO MI C
WEI G H TS
A ND
B " TH EO D O R E
WILLI A M
C O NT R IBU T I ONS F RO M
THE
OF
A RG ENTI C N I TRAT E
or
N I TRO G EN
S I L V ER
RI C HAR D S
A ND
G EO R G E SH ANNON F O R BES
CHEM I C A L L A B O RA T O RY
OF
H AR
V A RD C O LL EGE
THE QUAN T I T AT I VE S"N T HE SI S OF AR GE N T I C N I T RAT E AND THE
AT OMI C WE I GHT S DE NI T R OGE N AND SI LVE R
,
.
I NTRO DU CTI O N
.
The com p os ition o f a r g enti c nitrate is one o f the qu estiona b le p remises
i n the l ively ar g ument wh ich has recently taken p lace conce rning th e
1
atomi c w eights o f nitrogen and silve r
Although S tas s synthes es o f this
salt were ca rried out on a la rge scale and fa r mo re ca re fully than thos e o f
anyone b e fo re him s eve ral p oints concerning th e detail s o f the work we re
not inve stigated with th e care which modern p hysicochemical knowledge
demands Acco rdingly a repetition o f thi s wor k o f S tas s seeme d to b e
worth the trou b l e invol v e d ; and the follo w ing page s contain a b rie f
a ccount o f nine month s thought and la b or u p on it
The method ap p ears at fi rst sight to b e extreme l y sim p le consistin g
merely in the w ei ghing o f p u re s ilve r the dissolving o f thi s S ilve r in nit ri c
acid and the weighing o f the resulting nitrate The p reparation o f p u re
s ilve r havin g b een al ready solved the great di ffi cu lty consisted i n the
p rocu r i n g o f satis fa cto ry evidence that the nitrate was free from i m p u rity
and in ma k ing su re that none o f the silve r wa s lo st du rin g the p ro cess
The main emphasi s o f the subsequent discu ss ion will there fore b e laid on
these points th e o the r detail s being often indicated with but f e w wo rds
b ecaus e they s o close l y res em b l e the details o f p rev i ou s investi gations
carried ou t in th e C hemical L a b oratory o f H a rva rd C ol l ege
The res ea rch natu rally di v ide d itsel f into fou r s ections namely fi rst
th e p re p aration o f pu re mate rial s ; second the quant i tative synthesis ;
thi rd th e determ ination o f the pu rity o f the product ; and fou rth the final
resul t and i t s re l ations to the ta b l e o f atomic wei ghts Thes e will b e con
s i d e r e d in o rder
’
.
,
,
’
.
,
’
.
,
,
.
,
,
,
.
,
,
.
,
,
,
,
,
,
.
.
PREPARA TI O N O F P URE MATERI AL S
.
Al l the su b stances u sed i n the research were pu r i fi ed w ith very g reat
ca re Nitri c acid an d s ilve r w ere the two mos t im p o rtant
Ni tr i c ac i d wa s su pp l ied b y two fi rm s
E ach sampl e was wa rrante d
b y th e manu factu re rs to b e o f a ve ry high grade o f p u rity E ach w a s
redistilled twice j u st b e fore addin g to th e silve r u s i ng o nly th e m i dd l e
.
.
.
.
,
s p i a ll y G u y e No u v l l R e ch s l P o i ds At o m d e l a o t e S oc Ch P a r i s
Th r e ad e r i s r e fe rre d f o a o v i e t é s u m é t o t h e R p rt o f t h e I t e r a
1 90 5
a d
A m C h e m S oc 2 8 1
t i o a l C o m m i tt e e on At o m i c W e i g ht s J o u r
m a n y o th r p l a ce s ; a l s o t o C l a rk e J o u rn A m C h e m S oc 2 8 2 9 3
G ray
Tra n s C h e m S o c ( L on d o n ) 8 9 1 1 7 3
1
S ee
e
ec
,
e
e
.
.
r
e
.
’
c
n
n
.
en
.
,
.
.
,
,
n
n
,
e
.
.
r
.
e
.
.
.
.
z
.
.
,
,
,
.
o
.
,
n
,
n
n
,
,
,
,
47
48
TH E Q U A N TI TA V E S
G
YN T H ES I S
OF A R E N
TI C
N
IT RATE
,
E TC
.
p o rtion o f each distillate None o f the sam p les l eft a trace o f nonvolatil e
residue on eva p oration No di ff erence coul d b e detected in the results
.
.
b ecau se o f the diff erence o f sou rce o f the acid no r was th e constancy
,
destroye d when a singl e distillation only was made ( E xperiment
H ence littl e anxiety w a s felt concerning th e p urity o f this material
S i l v e r —The researches o f R i chards and Well s have S hown how to
p re p are S ilve r o f unquest i oned p urity P rel imina ry dete rminations 1 2
3 4 5 7 and 8 we re made on a sample ( A ) l e ft over from the above
mentioned res earch crystall i zed fi fteen times w i th nitr i c acid p reci p itate d
w ith formate and fused on p u rest charcoal b ut not el ectrolyz ed or f u sed
in hyd rogen
No 9 wa s made with a sampl e p re p ared b y P ro fessor
B axte r for h is final wo rk on b romine It had b een through the chlorid e
and fo rmate treatment electrolyzed fu sed in hydrogen cut with a s a w
etched with nitric acid boil ed with wate r dried at dull rednes s i n vacuo
and given u s ready to weigh We a re mu ch i nde b ted to him fo r fu rnishin g
th is check on ou r S ilver The fina l dete rm i nations were made w i th si l ve r
de r i ve d from several p re p arations The fi rst o f thes e ( C ) w a s r e cr y s ta l
li z e d sixteen times as nitrate from water and redistilled nitri c aci d and
then p reci p itated twice in su ccession with formate A p art o f the fi na l
fo rmate p ro duct w a s fu sed on the b est l ime in care fully p u ri fi ed hydrogen
made from aluminum and sodic hydroxide S am p l e D had b een p r e ci pi
t a t e d a s chlor i de reduced with b est alkal ine su g a r washed free fro m
ch l or i d e d i s s o l ved i n n i tr i c acid fi lte red and crystall i z ed a s n i trat e i n
m s i x t i me s from n i tric a cid d i st i lled i n a p latinum condenser
pl a ti n u
C entr i fu gal treatment e l im i nated the mothe r li quor The last c ro p o f
crystal s w a s p reci p i tated w i th fo rm ate in a si l ve r dish washe d free from
ammonia and fu sed in a cu p o f p u re l ime S am p l e F was o b tained b y
th e e l ectroly s i s o f a b utton o f very p u re s il ver from C o l orado wh i ch h a d
b een fi fteen times recry stall i z e d a s nit rate p reci p i tated w ith formate and
fu se d on l i me S ample s C D and F were al l cleaned b y etching and the n
p u ri fi ed b y electrolysi s th rou gh a n i trate solut i on m ade from some o f th e
s ame s il ve r and the p u rest n i tr i c aci d
They were then fused se p ara te l y
on a wel l seasoned l ime boat i n a new porcel ain tu b e in an atm os p here
o f pu re electrolytic hyd rogen Th e H empel stoppers fi tted s o well that
th e p ressu re coul d easily b e reduced to a fract i on o f a mill i mete r b y a
The heat i ng wa s a ccom p l i she d b y a l arge
G e r y k oil p um p when desired
H e ra e u
s e l ect ri c fu rnace wh i ch fu sed the silver w ithout overheat i ng any
p art o f th e tu b e In a ll cases the in i tial fu s i on w a s com p l ete d in hydro g e n
at atmos p heri c p ressu re b ut i n ha l f the fu s i ons th e tu b e wa s evacuated
b e fore the temperatu re was lowered No S p u rting o r b oil in g cou l d b e
o b served th ro ugh the glass window wh en the pressu re wa s redu ced and
.
.
.
.
,
,
,
,
,
,
,
,
,
,
.
.
.
,
,
,
,
,
,
,
.
.
.
,
.
.
,
,
,
,
'
.
.
,
.
,
,
,
,
.
,
,
,
.
-
,
,
.
-
.
.
,
.
,
50
TH E
Q U A N TIT A TI V E
S
YN T H ES I S
TH E S "NTHES I S O F
G
OF A R E N
ARGENTI C
TI C
N
IT RA T E
,
E TC
.
NI TRATE
.
The m aterials having been prepared the next step wa s to com b ine them
Thi s com bination mu st take place in a vessel wholly f ree f rom a s us
p i ci o n o f solubility on the one hand and arranged s o as to p revent los s o f
material on the other hand At the same ti m e it w as important to be abl e
to evaporate and to w eigh the a rgentic nitrate in the same v e s sel A f ter
a ca reful consi deration o f the some w hat confl icting clai m s o f these requ ire
ments it wa s decided to carry out the process in small round b ottome d
flasks o f fu se d qu a rtz o f from
to
l ite r capacity ; with necks
C oll a rs o f platinum
1 1 cm in len gt h and 6 to 9 m m in inte rnal dia m ete r
wi re p rovi ded with loops per m itted th e suspension o f thes e flasks from
th e hook o f the Tr oe m n e r balance B efo re weigh ing they we re heated i n
the oven to be presently described to 2 50 fo r at least hal f an hou r a
m oderate ai r cu rrent sweeping th rough the m all the ti m e
The cover
ings were then l i fted and each flask was re m o v ed by a hook o f platinum
wire seal ed into a glass rod and trans ferred to a large desiccato r p ro
Two flasks s imilar in weight and su rface
v i d e d with a su ita b l e su pp ort
were t reated in the same w ay and kept in the sa m e desiccato r A f te r
two hou rs nea r th e balance the fi rst flask was weighe d against a tare its
wei g ht b eing determined b y substitution o f the fi rst by the second fl ask
and a few s m al l w eights U pon re m oval from the desiccator both flasks
absor b ed moi stu re from the ai r o ften to the extent o f
gram b ut
they soon reached constancy with respect to one anothe r which was al l
that wa s needed No final weighings were made when the hygrometer
i n the weighin g—
room stood abo v e 4 0 and unde r thes e ci rcu m stances
flasks coul d b e weighed on successive days with variations not exceedin g
gram
A new Tr o e m n e r balance sensitive to
m g was availa b l e fo r the
res earch Th e b ras s weights w ere ca re fully standa rdized at the b e gin
ning o f the year and aga i n upon startin g the fina l ser i es ; and the ride r
also was cali b rated and the necessary co rrection employed
F o r co r
rection to the vacuum standard
w a s adde d to e a ch apparent
gra m of a rg e nti c nitrate and
was subtracted from each apparent
g ram o f S ilve r Thi s was on th e assum p tion that the t w o s p ecific gravities
concerned w ere respectively
and
that o f the b rass weights
b e i ng
The sil v er was now weighed by substitution and carefully pushed
down the nec k o f the flask wh ich wa s hel d meanwhile in a ho rizonta l
position to avoi d breakage Next the who l e was trans fe rre d to a large
clean empty desiccator whose sides had b een moistened ; and the flas k w a s
laid on a su itabl e su p po rt o f gl ass and platinum tilted 4 5 from the ve r
.
,
,
.
,
.
-
.
.
.
,
.
°
,
-
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,
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,
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,
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,
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,
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,
,
,
.
,
,
°
TH E S
Y N T H ES I S
O F A RG E N
TIC
N
I T RA T E
51
.
tical A su f ficient quantity o f p u rest nitric acid m ixed with hal f its
volume o f distill e d wate r was p ou re d in from the platinum cru cibl e into
which i t had j ust been distilled The cover o f the desiccator wa s re p laced
but its stoppe r w a s first removed and covered with a watchglas s and a
clean be a ke r The appa ratu s w as now k e pt all night in a warm place
between 4 0 and 5 0 C ; thu s the s ilve r when dissolved remained in solu
tion though the volume was re stricte d to 2 cm o f solution p e r gra m o f
nitrate I n the mo rning th e p ro ces s was found to b e com p l ete A fter
washing down the neck with a f ew d rops o f fre s hly distille d w ater th e
fl a s k was place d in t h e oven as be fore Th e de s iccato r w a s washed with a
l ittl e wate r the w ash ings being tested fo r S il v e r in the neph elo m eter ; i f
any had b een found it might have b een feared that more had esca p ed b ut
as no t race w a s e v e r found it was in ferred that the
long incl ined neck had caught al l the s p ray
Attention is no w called to the ap p aratu s for e v a po
ration
The main featu re o f this w a s the com b ined
del i v e ry tu b e fo r the ai r cu rrent and hood for the
p rote ction o f the contents o f th e flas k This hoo d H
with its ingre ss and egres s tubes I and E i s shown
i n the diagram ( figu re
The d ry ai r used to
swe ep out the aqu eou s and nitrou s va p ors entered
f rom the p u r i fying train at G where connection was
made b y a well —
ground j oint ; p as s in g th rough the
tube 1 it escape d into th e body o f th e flas k and out
th rou gh its neck A s ide tube E wa s attached to
H for connection with a wate r pum p
Th e flas k
rested on a triangl e o f p latinum wi re attached to a
glass tripod a n d the whol e was p laced in a
l iter
beake r which se rved a s the oven A sand b ath e n
a b le d this to b e k ept at any desired tem pe ratu re
The cover o f the b eake r was o f sh eet coppe r p ierced
w ith th ree holes fo r the tu b es I and E and for the
thermomete r A s no nit rou s fum es esca p ed into
A pp a a t us f
E p
the oven thi s cove r remained intact In th e p re l i m i Fi g I —
a ti ng A q u e u S l u ti
S e c ti
a b u t half c t u a l i e
nary trial s the extra tu b e Q was l ackin g th e tu b e
F 11 k f f
d
t
I b e i ng extended to take I t s p l ace
Th e p a rt wh i ch
ly
f ‘b
had p roj ected into the b o dy o f the fl ask w a s treated Q au f é iufié hi g i d d
b
1 t
”
W i th hot d i lute n i tr i c ac i d and I nvest i gated for S i lve r
,3;
.
.
,
,
,
.
°
°
.
.
,
.
.
,
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,
,
,
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1
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.
,
,
,
,
.
,
,
-
.
-
,
-
.
.
,
,
,
.
,
r
.
.
o
r
va
o
ons .
o
3
o
on
,
or
s z
a
.
.
e
o
a
s
er
s
a
e
'
56
1
p ass i
In
t
n
g
p ra t i
m e n f o r e va
A cad , 2 6 2 5 8
.
,
i t mi g
o
ht
n
b e,
t d th a t
no e
g s o l ut i on s
of
on e
sod i c
u s u s d a som wh a t s i mi l a r a rra ge
s u l ph a t fi f t e n y a rs ago ( P roc Am
of
e
e
e
e
e
n
.
.
52
TH E Q
U A N TIT A TI V E S Y N T H E S I S
i n the nephelomete r
G
OF A R E N
TI C
N
IT RAT E
E TC
,
.
Occasionally some w a s fou nd b ut the correction s
requ ire d w ere not large Neverthel ess the p ossi b i l ity that the fu se d
nitrate had attacked the glass was always distu r b ing and the i n con v e n
i e n ce and uncertainty o f this correction ma de its el imination desira b l e
Accordingly in th e final determ inations a section o f quartz tu b in g Q
3 mm in diamete r and 1 5 mm lon g was firmly attached to a platinum
w ire and lowered till it b arely p roj ecte d into the body o f th e flask Th i s
su p porting wire hoo k ed i nto the collar s o that the quartz tu b e coul d b e
remove d whil e the s ilve r w a s dissolvi n g D u r i n g th e eva p oration how
eve r i t was i n p lace and th e end o f the gl ass delivery tub e w a s S ho r tened
and drawn down to fit into i t The glas s tu b e w a s still tested as b e fore
b ut no silver w a s ever recove red from it H ence the flask and th e quart z
tu b e mu st have retained all the silver ori g inally weighed out
The eva p o ration o f the l iqu id wa s easily and q uick l y condu cted in th i s
a pp aratu s I f th e flask wa s not more than hal f full and th e air p assed
through the dryin g t rain no faster than two b u bbl es p e r s econd i t w as
p ossibl e to maintain the tem p eratu re o f th e oven at 1 2 5 without ris k o f
e b ull it i on The va p ors drawn out a s b efo re descri b ed p assed fi rst th rou gh
a U tu b e fill ed with mo ist gl as s b eads and j ust seal ed with water a fter
wards th rough a tower o f cau st i c al k al i to take out nitric a cid which mi g ht
attac k th e water p ump W hen the li q u id b ecame coated w i th a fi l m o f
c rystal s the tem p eratu re was lowered to
b u bb les o f va p o r n ow
f ormed g radua ll y unde r the c rysta l l ayer and the s li ght s p atterin g cau se d
b y thei r ru p ture coul d b e s een on the ins i de wal ls o f th e flask The oven
was now su ddenly cool ed s o that the va p ors from the hot l iqui d condens
in g on the walls o f the flask washed down the crust wh i ch had forme d
du ring eva p oration U p on continu ing the heatin g a porous c ru st w a s
s oon fo rm ed
unde r which the formation o f steam cau sed no s p atter i n g
F i na l ly the tem p erature was rai sed g radually wh il e th e last t race o f
li q u id w a s disap p earin g Th e sol i d w a s dr i ed for a quarte r o f an hou r
t o insu re com p lete fu s i on
at 1 50 in the dark and then heated to
not only o f the ma i n po r t i on b ut al so o f any p o r tions p roj ected on th e
u pp er walls o f the flask Th e tem p e ratu re was soon lowere d to
w hich su f ficed to kee p the mass in fus i on and the ai r cu rrent was con
ti n u
Then i n su b du ed li gh t the flas k w a s l i fted out
e d fo r an hou r
b y a loop o f p latinum wi re p assed through i ts collar p lace d on a net
wo rk o f p l atinum w ire and ti l ted i n all directions to cause the n i trate to
so l idi fy in a thi n laye r on the wall s Once this p recaution w a s ne gl ected
and th e flas k was cracked b y th e contraction o f the nitrate on coo l in g
.
,
,
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,
,
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,
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,
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,
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,
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,
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,
°
.
-
,
-
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,
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,
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,
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,
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,
,
.
°
.
,
,
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,
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,
,
,
,
.
.
1
Th i s
th e
e
t
em
p e ratu re
x p os d s t e am
e
.
an d
th e o
h y
T
e
do
th rs
e
n ot
t
b
e
o
i n d i ca t e
re co r d e d l a t e r h av e
th e e
xa ct
m ee
t
in
g
-
n ot
p
oin
t
b e en
of
co
th e
rre ct e d
sa l t
.
f or
TH E S
Y N T H ES I S
G
AR E N
OF
TI C
N
IT RAT E
53
.
b ut still hot the flas k w ith i ts con
tents was trans fe rred to its su pp ort o f p latinum wire i n a l a rge ti g ht
desiccato r whi ch w a s w ra pp ed in a b lac k cloth and le ft near the b al
ance ove r night Then the weight o f the flas k w a s determine d a s b e fo re
Thu s in th e enti re cycl e o f ope rations noth in g b u t p latinum clean glass
W hen the nitrate was wholly sol i d
,
,
,
.
.
,
,
pu re ai r tou ched the outside o f the flas k
It remains to b e p roved that no silve r was ca rried ou t b y the ai r cu r
rent This w a s in fe rred b e cau s e no trace o f S ilve r was eve r found i n the
U tu b e th rough wh ich all the vapo rs pass ed ; bu t more definite ev i dence
w a s ob t ai n e d by re dis sol v ing two finished determinations and e v a por a t
i n g them a gain with the cu stoma r y p recau tions
a nd
.
.
-
,
.
D e te mi n ti n
n u mbe
r
a
r
A gNO S
o
o
n ce
eva p a te d
or
.
th i c e
e va p a ted
t w i ce
e va p a t e d
A gN0 3
or
.
1 0 6893 3
1 4 20 1 1 4
A gNOa
or
.
1 0 689 28
14 20 122
.
To“ "
.
0 000 1 3
0 0 00 1 3
1 0 689 20
1 4 20 1 2 7
.
.
r
.
.
.
.
.
0 00 00 0
i
.
The fi rst residue in the case o f No 1 5 w a s sl i ght l y dark ene d b y pr o
longed heating ; stil l no fi xed tendency towa rd eithe r loss o r ga i n i s shown
b y thes e figu res an d th e rel ia bi l ity o f the method i s demonstrate d
Two p relim ina ry ex p e r i m ents we re not fi nished and one w as rej e cted
b ecau se o f k nown e rro r S i x p rel iminary determ i nations carr i ed ou t i n
the way j ust des c ri b ed gave results va ryin g from
to
p arts o f nitrate from
p arts o f S ilve r in th e m ean
Th i s
i s ve r y nearl y the sam e a s the fi nal se ries gi ven l ate r b ut b ecau s e
o f sundry i rre gula rities t he s e determ inations a re i ndividually mu ch l es s
t ru stworthy than the latte r One o f th e p rel iminary dete r m inations w a s
made w ith a p ie ce o f s ilve r k i ndly gi ven us b y P ro fes so r B axte r fo r
It gav e
t he sake o f com p arison and fo r wh i ch we are mu ch i ndebted
a resul t p erha p s highe r than the avera g e b ut not b y an amount greate r
than the l im i t o f erro r o f the ex p er i m entation at that time It i s g reatly
to b e regretted that thi s p ie ce w a s not examined a fter every detai l o f the
p roces s ha d b een pe r fected b ecau se the com p arison woul d have been i n
t e r e s ti n g although not at all ess ential fo r the com p l etenes s o f ou r work
{
When it a p peared im p ossib l e to imp rove u p on the detail s o f th e e xpe r i
m entation a final se rie s o f s i x consecutive determ inations w a s carr i e d
ou
In each case exce p t No s 1 4 and 1 5 the ar g en
t w i th all p oss i bl e care
ti c nitrate was maintained fo r an hou r in a fu sed condit i on whi l e d ry a i r
swe p t ove r it I n No 1 4 only one q ua rte r o f an hou r w a s al l owed
whereas i n No 1 5 the fu sion wa s p rol onged fo r three hou rs S am p l e D
.
.
,
,
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,
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,
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,
-
.
,
.
.
.
54
TH E Q
U A N TITA TI V E S Y N T H E S I S
s il ve r was u s ed i n syntheses
other th ree
of
O F A RG E N
and
1 0, 1 1,
TI C
N
IT RA T E
E TC
,
and sam p l e
1 2,
.
F i n th e
.
Th e S y n th es i s
No
n
to
ro
r ro r o
ec
r
ra
r
a
ro
r
.
G m
ra
.
ar
s
o
r.
.
p b ab le e
f th i s ave a g e c m p u t e d f m th e e su l ts w h e n
th e n e xt d i m l p l ce i s n l y
w h ll y n e g li g i b l e q u a n t i t y
ep et i t i n f th e p ce ss w u nn ece ss a y
Th e
ed
He n ce
s
o
ar
i"n
1
ra
ri
o
’
.
.
W e i gh t f W e i g h t f g e n
f u s e d g e n t i c t i c ni t t e m d e
ni t a t e
f m
p a ts f s i l v e
( i n vac u u m )
O
G m
1
f A r ge n ti c Ni tr a te
we i gh " f
s 'l ve
f
( u s evac
d u um)
of
s y thes i s
.
o
o
a
o
r
a
,
,
o
o
a
as
ro
r
car
r
ro
o
.
.
th i s ratio j u st found to b e
S tas obtained an ave r
a ge o f
from n i ne dete rm inations which ranged from
to
B ette r agreement than that exhi bi ted b y the above ta b l e coul d hardly
b e des ired or expected a s the g reatest deviation co rres p onded to l es s
than
m g in the weight o f th e a rgenti c nitrate Thi s s eries demon
s t r a t e d that it i s not neces sary to u se very la rge amounts o f mater i a l
i n o rder to attain a ve ry high o rde r o f p recision i f only the detail s o f
ex p e rimentation are fi tti ngl y a rran g ed
S atis factory a s t hi s se ri es o f results appears to b e it i s b y no mean s
to b e accepted withou t fu rthe r question a s re p resentin g the t r u e w ei ght
o f a r g enti c nitrate to b e o b taine d from p u re silve r
E ven in this fu se d
sal t p re p are d unde r such favo rable conditions seve ral impu rities might
exist ; and b e cau se in each case th e method o f treatment was the same
these impu ritie s might b e constant in amount and there fo re not pe r ce i v
a b l e in the results Accordingly attention was now directed to the search
fo r these i m p uriti es ; and t h is part o f the investigation was found to b e
the most a rduou s and time consuming part o f it The fol l ow i n g section
dis cusse s this matte r
F or
,
,
.
.
,
.
,
.
,
,
,
.
,
-
.
.
TH E
P U RITY
G
FU S E D
O F TH E
AR E N
THE P URI T" O F THE F U SED
TI C
N
IT RAT E
ARGENTI C
55
.
NITRATE
.
The first i m pu rity fo r which search was made wa s ai r W hi l e c rysta l s
o b taine d from solution a l thou g h a l way s contain i n g solvent may b e s u
p
p osed to b e free from a i r th e fu sed mate ria l can not w i thou t q u est i on
be assu me d to be free from this im p u r i ty The only manner o f a pp roach
in g this q u estion seems to b e to fu se the sal t a se cond time i n a vacuu m
in orde r to detect a p ossi b l e los s o f we i ght This S tas di d i n a s ingl e case
w ith a negat i ve result
Neverthel ess a s ingl e ex p er i ment even o f
S tas s does not car ry with it mu ch weight ; the re fo re the test deserves
repetition
This w a s carr i ed out i n th e p resent ca se w i thou t gre at di f ficulty on
fi ve o f the p rel im inary dete rminat i ons Th e flas k s containin g the argen
tic nitrate wh i ch had b een fus ed fo r an hou r i n ai r we re lowe red into
mammoth test tu b es —lon g tu b e s o f so ft glass
cm in d i amete r
s ea l ed at the lowe r en d and s c ru p ul ou sly cl ean A hood was p laced ove r
th e mouth o f the fla s k to p revent fra gments o f gl as s from enter i n g and
the tu b e w a s drawn down i n two large conve r g in g b last flames A glas s
tu b e w a s fu se d on and connected w ith an e ffi c i ent mechanical hand
p um p ; s everal exhau stions followe d b y admiss ion o f dry ai r excluded
al l mo i s tu re F i na ll y the system w a s reduced to 2 mm and s eal ed an d
h eated to
A fte r having b een maintaine d i n a state o f fu sion in the
da r k for hal f an hou r the salt w a s cool ed in the u su al caut i ou s fash i on
and ai r w a s admi tted ve r y s l ow l y
The flas k wa s p l ace d i n a desiccato r
over night and weighe d Th e p roduct w a s a l ways S li ghtl y d i scolo red
i ndicatin g decom p os i tion b u t show ed no s er i ou s l oss in wei ght
.
,
,
,
.
,
,
.
.
,
,
’
,
.
.
-
.
.
,
.
,
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,
.
,
,
,
,
.
.
,
,
.
Th e E ff e ct
mi n i n
O ri
G
8
8
8
9
10
.
.
.
.
.
ra
o
f
Fu
s i on i n V a cu
um
i n al
ms
.
0 4489
7 5 81 3
54 1 70
87 850
7 6 3 81
We i h
G m
ra
8
8
8
9
10
.
.
.
.
.
f
s
.
er
.
0 44 7 7
7 581 0
54 1 7 0
8783 7
7 63 74
i
0
0
0
0
0
.
.
.
.
.
0 00 1 2
00 0 03
00 0 00
0 00 1 3
000 0 7
gram s o f sal t l o st in all
g ram This is l ess than 1
i
p art in
and may sa fely b e re ferre d to the trace o f de com p os i
t i on ind i cated by the p al e b rownish coloration Not only i s i t reasona bl e
to su pp os e that bu t l ittl e ai r i s dissolve d ( fo r acco rdin g to the l aw o f
H enry nearl y all o f i t shoul d have b een ex p ell ed b y this treatment ) b ut
al s o one i s l e d to infe r that ve ry l ittl e water remains to b e ex p elled This
F o rty - fi v e
.
-
-
.
.
56
TH E
G
Q U A N TIT A TI V E S Y N T H E S I S O F
AR E N
TI C
N
IT RA T E
,
E TC
.
matte r i s not ho w eve r s o simply settled ; the final testing o f it cost mu ch
l a b or
I t has been o rdinarily assume d that water is enti rely expell ed from crys
t a ll i z e d o r eva p orated salts upon fusion
This is in all p roba b il ity the
case with sodi c and potassic chlorides and othe r salts w hich fu se at high
tem p e ratu res and S how l ittl e a f finity for water Whether o r not this was
the case w ith argentic nitrate which at 2 1 0 is m isci b l e with wate r in al l
p roportions was a q u estion whi ch re q u i red experimental investigation
B es ides the conservation o f we ight on fusion in a vacuu m another argu
ment may b e addu ced to S how that most o f the wate r h a s been driven out
The com b ining weight o f a rgenti c nitrate seems to b e nearly i n d e pe n d
ent o f the time o f its fu sion in a cu rrent o f d ry ai r as is shown by the
followin g ta b l e
,
,
.
.
,
.
°
,
,
.
.
,
.
D
et e
r
m nat
i
1
i on
“
l
m
i i ggf
f
.
k
m
W e i gh t
of
Ag N0
3
s
15
r
1 h ou
3
o rs
h u
1 5 7 480
.
It shoul d b e stated that th e l ast residu e was slightly disco l ored and
i ncreas ed
gram u p on a su b se q uent evaporation with wate r and
nitr i c acid ; hence a rea l loss of weight durin g the extra period o f fus ion is
indicated ; b u t this was p roba b ly du e to decom p osition o f the salt rathe r
than to escape o f wate r ; the refore the ta b l e b ears out the content i on stated
above In any case this loss amounts to much l es s than a unit in th e last
deci m a l p lace
O rdinarily in the p ast t h e investigato r has b een satisfied w i th su ch an
outco m e and has gone no fu rther B ut in this case we were anxiou s to
l eave no ston e untu rned ; and acco rdingly a drasti c metho d of treatm ent
w a s ado p te d which p ermitted n o trace o f wate r to escape b eing weighed
This was to decom p ose completely th e ar g enti c nitrate by heat and to p ass
the gaseou s pro du ct o f the decomposition th rough a weighed tu b e contain
i n g phospho ric oxide
A ha rd glass co m bu stion tu b e was b ent and drawn out in t he manner
shown in figure 2 the space b etween C and D being packed w i th glas s
wool Into the space bet w een B and C w as then intro duced abou t 50
grams o f argentic nitrate which had been c rystallized from nitri c acid
barely fu se d in po rcelain cooled and pounded in a m ortar The tube
was heated to 220 in an ai r b ath fo r an hou r i n a s tream o f dry air passed
in th rough A The a rgentic nitrate S houl d now be in a condition some
what comparabl e to that o f the quantitative determination F inally a
,
.
.
,
,
.
.
,
,
.
,
.
,
°
.
,
,
-
.
.
,
T H E Q U A N T I T A T I V E S YN T H E SIS O F A RGEN T I C N I T RA T E
58
,
E TC
.
be fore p ass i n g o v er t h e copper ; it ha d b ee n he a te d i n the d r y a i r to re m o v e
m oi s t u re
To eli m i na te t h e po s s ibilit y o f wa te r i n t h e copper gau ze and to te s t t h e
a pp a ra t u s a bl ank r un w a s mad e re m o v i ng t h e d eco m po s itio n t u be and
o x i d izi ng t h e copper w it h d r y a i r H ere the pe n to x i d e t u be lo s t
g r am a re su lt wh ich i nd ic a te d n o error i n t ha t p a rt o f t h e proce s s
I t i s n ot w ort h wh ile to recor d t h e i nd i v i dua l e x peri m e n t s b y wh ic h t h e
gr adua l i m pro v e m e n t s i n a pp a r a t u s and man ip u l a tio n w ere te s te d tire
s o m e and ti m e co nsum i n g a s t h e s e w ere i n e x ec u tio n B y t h e ti m e s e v e n
e x peri m e n t s had bee n per fo r m e d it was cle a r t ha t the fu s e d a rge ntic n itra te
co u l d n ot co n t a i n o v er
per ce n t o f wa ter E v e n o f t h i s sma ll am o un t
a p a rt w a s u nd o u bte d l y du e to n itric pero x i d e ; f or t h e copper gau ze was
n ot e n o ugh to e f f ect a co m plete d ecom po s itio n o f t he gas e s P ass i ng c a r
bo n m o n o x i d e t h r o ugh t h e a pp a r a t us wh ile t h e d eco m po s itio n was i n pro g
re ss le ngt he n e d t h e e ff ecti v e li f e o f t h e re du ce d copper b u t i n tro du ce d
ot h er co m plic a tio ns ; and t h e add itio n o f a s eco nd t u be o f h ot gau ze a
m eter lo n g w a s s till i nad e q ua te
Th e n e x t s tep was to s ec u re a copper su r fa ce s o l a r g e t ha t a ll th e n itro
ge n o x i d e re su lti n g f ro m t h e co m plete d eco m po s itio n o f 5 0 gr ams o f
a rg e n tic n itr a te co u l d be re m ov e d and t h i s w it h o u t i n cre as i ng t h e co m pli
c a tio ns o f t h e a pp a r a t u s P o wd ere d copper o x i d e loo k e d pro m i s i n g a s a
s o u rce o f t hi s m et a l b u t it mus t be mad e f ro m p u re ma teri a l s to av oi d
t h e p re s e n ce o f d etri me n t a l i m p u ritie s P u re electr o l y tic copper ( Merc k )
w a s d i ss ol v e d i n n itric a ci d e va por a te d to d r yn e s s i n porcel a i n and v e r y
g r adua ll y i gn ite d w ith co ns t an t s tirri ng to po wd er y o x i d e A h a r d g l ass
t u be 3 0 cm lo ng and 3 c m i n ter na l d i am eter w a s u s e d to co n t a i n it ; t h e
e nds w ere d r awn d o wn co nv e n ie n tl y and t h e o x i d e w a s re du ce d a t a v er y
m o d era te he a t w it h c a rbo n m o n o x i d e prep a re d a s u sua l e x cept t ha t it
N e a rl y 3 0 0 gr am s o f copper o x i d e w ere
w a s fina ll y d rie d w ith pe n to x i d e
pre s e n t ; t h eref ore t h e proce s s was v er y te d io u s S i n ce the gas h ad to p ass
thro ugh i ts p u ri fy i ng tr a i n a t a m o d er a te r a te o f s pee d W ith t h i s l a r g e
mass o f fin el y d i v i d e d copper t h e gl a ss w ool ( f ro m C to D i n t h e d i a
g ram ) was n o l o ng er n ece ssa r y t h ere fo re i t was n o lo ng er u s e d N o tra ce
o f po wd ere d n itr a te e v er a ppe a re d be y o nd t h e copper
A cle an pe n to x i d e t u be w it h g l as s s topcoc ks w a s re fi lle d w it h r e s u
b
li m e d pe n to x i d e and g l ass w ool ; d r y a ir was p ass e d thro u g h f or te n m i n
u te s to assu re co ns t an c y A du plic a te t u be was a l s o prep a re d f or a co un
t e r po i s e and e x tr a o r d i na r y prec au tio ns w ere t ak e n i n protecti n g a n d
w ei gh i ng t h e s e t u be s A s an o t h er prec au tio n it s ee m e d a l s o e x pe d ie n t to
prep a re a r ge n tic n itra te n e a rl y a s p u re as t ha t us e d i n the d eterm i na tio ns
f or f e a r o f hyg ro s c o pic n itr a te s S ilicic a ci d and amm o n i um sa lt s w hic h
w o u l d y iel d wa ter wh e n d eco m po s e d A m o d era tel y p u re sa lt was r e cr y s
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T H E P U RI T Y O F T H E FU S E D AR GEN T I C N I T RA T E
59
.
.
f ro m n itric a ci d fi ltere d p recipit a te d w ith f or ma te wash e d f ree
f ro m amm o n i um sa lt s and fu s e d o n li m e i n the b l as t T he b u tto ns w ere
ta l li z e d
,
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,
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etc h e d and d i s s ol v e d i n f re s hl y d i s tille d n itri c a ci d i n J e na gl a s s and
t h e sa lt w a s cr ys t a llize d w i th am ple p rotectio n aga i ns t amm o n i a d rie d
ce n tri fuga ll y and k ept i n a cle an ti gh t d e s icc a tor T here w a s n o amm o n i a
i n t h i s pro du ct B e f ore u s i n g it was fus e d i n pl a ti num
In the fi r s t d eter m i na tio n o f t h i s s erie s t h e a r g e n tic n itr a te was h e a te d
too hot
and the gas e s c am e o v er s o fas t th a t t h e re du ce d copper
w a s o n l y su per fi ci a ll y a tt a cke d ; e v e n s o it wa s vas tl y m ore e f fi cie n t t han th e
gau ze B ec aus e ho w e v er s o m e n itri c pero x i d e s till e s c a pe d thi s e xpe r i
m e n t a l s o had to be re j ecte d a p a rt o f t h e
per ce n t i m p u rit y w hich
it i nd ic a te d bei n g u nd o u b te d l y du e to n itro u s fum e s
T he a pp a r a t u s w a s n o w im pro v e d b y s e a li ng o f"
?the e nd ( A ) o f the t u be
a f ter t h e a rge n tic n itr a te had bee n fu s e d f or a lo n g ti m e i n a c u rre n t o f d r y
a ir Moreo v er t h e l as t tr a ce o f r u bb er e x po s e d to n itro u s fum e s w a s
eli m i na te d b y p ro v i d i n g an a cc u r a tel y g ro und j oi n t b et w ee n the d e com
po s itio n t u b e and the copper o x i d e T he p roce s s w a s co ndu cte d s o s lo w l y
a t 4 90 th a t t h e a r g e n tic n itr a te co u l d be e n ti rel y d eco m po s e d to p u re
s po n gy s il v er w itho u t e x h aus ti n g a ll t h e copper C a re w a s t a ke n to h av e
t h e v e ry p u re a r g e n tic n itr a te i n a s t a te co m p a r a ble to th a t u s e d i n the
d ete rm i na tio ns T he sa lt a fter i ts preli m i na r y tre a tm e n t i n pl a ti num s til l
co n t a i n e d a f e w cr ys t a l s o f un fu s e d n itr a te ; a ccor d i n gl y i n the t u b e it w a s
he a te d e v e n l y a t 2 2 0 w it h shak i n g to d i s lo dg e s te am b u b ble s e xa ctl y a s
the d eterm i na tio ns h a d b ee n U nd er the s e co nd itio ns reli a ble re su lt s
w ere o b t a i n e d In N o 2 5 a s eco nd w ei gh e d pe n to x i d e t u b e pl a ce d i n
t and e m w ith the fi r s t s ho w e d n o ga i n i n w ei ght ; he n ce the fi r s t t u b e
c au ght a ll the wa ter va por T he re ma i n i n g n itroge n w a s d ri v e n o u t b y
p u re d ry a i r be fore w ei ghi n g T h a t wa te r va por w a s a ct ua ll y pre s e n t
was s ho wn b y t h e m elti n g o f pho s phoric pe n to x i d e i n the fi r s t t u be
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“
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Wa te r
O b ta i n e d b y D e compos i ti on
p eri me n t
Ex
n u mb e r
.
We i g h t
A g NO s
25
26
27
of
.
o
f A r g e n ti c N i tr a te
a i n i n we i g h t
of d ry i n g tu b es
G
.
Gr a m
Gra m
53
2
44
0 00 1 5
0 00 1 1
0 00 1 4
50
0 00 1 3
.
.
.
.
er e n ta g e o f
at e r fou n
P
w
c
d
P er
ce n
.
t
0 00 2 8
0 00 20
0 0 03 3
.
.
.
.
Thu s it i s cle a r t ha t le s s t han
per ce n t o f wa ter was hel d b y the
a r g e n tic n itr a te a f te r fu s io n Th ere w a s o n l y o n e ot h er s o u rce f ro m
wh ich thi s m illi g r am or s o o f wa ter m i ght h av e co m e nam el y f ro m t h e
.
,
,
T H E Q U A N T I TAT I VE
60
S"
N T HE S I S O F AR GE N T I C N I T RA T E
,
E TC
.
copper u s e d f or t h e re du ctio n o f t h e n itro us fume s L e s s t han
g r am o f hyd ro ge n ret a i n e d b y 3 0 0 g r ams o f copper or le ss t han o n e p a rt
i n a m illio n w o u l d hav e bee n e n o ugh to c au s e t h i s e ff ect h e n ce it s ee m e d
r ash to assum e t ha t t h e wa ter d i d n ot co m e f ro m t h i s s o u rce A S mu ch
hyd ro g e n as t h i s m i gh t hav e co m e f ro m a tr a ce o f m oi s t u re i n t h e hun
d re d liter s o f c a rb o n m o n o x i d e u s e d f or t h e re du ctio n o f t h e copper
Th e q u e s tio n t hu s r a i s e d was c a p a ble o f bei ng i nv e s ti ga te d F o r t h i s
p u rpo s e t h e mass o f copper re du ce d j u s t a s it w o u l d hav e bee n f or o n e o f
the p rece d i n g e x peri m e n t s w a s t w ice o x i d ize d b y a v er y l a r g e v o l um e o f
p u re i gn ite d a i r d rie d w it h t h e u sua l p o t ash to w er s and fina ll y w it h p h o s
T h i s a i r hav i ng bee n a lre ady p ass e d o v er re d h ot
ph o r i c pe n to x i d e
c u pric o x i d e i n a ha r d gl as s t u be and t h oro ugh l y d rie d b y pe n t o x i d e co u l d
ha r d l y bri n g w it h it any wa ter wh ich co u l d be t ak e n u p b y t h e f ollo w i n g
t u be o f t h e sam e ma teri a l On o n e o f t h e s e occ as i o ns
g r am o f
wa ter was fo und and o n an ot h er
g r am P o ss ibl y s o m e o f th i s may
hav e co m e f ro m t h e a t m o s p h ere du ri ng t h e man ip u l a tio n o f t h e t u be s ; b u t
a s i m il a r am o un t mu s t be su ppo s e d to hav e bee n t ak e n du ri ng e a c h o f t h e
pre v io us d eter m i na tio ns H e n ce it s ee ms to be per m i ss ible to su btr a ct
t h e av er ag e
g r am f ro m t h e av er ag e re su lt o f e x peri m e n t s 2 5 2 6
and 2 7 nam el y
g r am T hi s le av e s o n l y
gr am as t h e max i
mu
m am o un t o f wa ter h el d b y 50 gr am s o f c a re fu ll y fu s e d a r g e n tic n itr a te
i n tro du ci n g an error o f o n l y 1 p a rt i n
A S t h e av er a ge o f
t h e fina l s erie s le d to a va l u e a t ri fl e o v er
g rams as the w ei gh t o f
n itra te o bt a i na ble f ro m
g r ams o f s il v er t h e correcti o n to be a pplie d
f or wa ter re du ce s t h e re su lt o n l y to 1 5 7 4 7 9
P o ss i b l y n o t e v e n as mu ch
wa ter a s thi s was pre s e n t i n t h e quan tit a ti v el y mad e a r g e n tic n itra te
b ec aus e t h e rel a ti v e su r fa ce e x po s e d f or d ry i n g was n o t s o g re a t i n the
l o n g na rr o w t u be j u s t u s e d as it was i n t h e qua rtz flask e m plo y e d f or
e x peri m e n t s 1 0 to 1 5
to
Th i s un i m p ort an t c hang e i n t h e syn t h etic re su lt f ro m
was t h e o n l y a pp a re n t o u tco m e o f t he s e te d io u s and o f te n e xas per a ti n g
e x peri m e n t s o n t h e d ecom po s itio n o f t h e n itr a te ; b u t i n re a lit y m ore was
Sh o wn b y t h e m Th e e x perie n ce fu r n i sh e d to t h e e x peri m e n ter s a s tri k
i n g e xam ple o f t h e e ss e n ti a l i m port an ce o f t ak i ng as mu c h c a re i n d eter
m i n i ng a s m a ll c o rrecti o n as i n d eter m i n i ng t h e quan tit y to be correcte d
I t m o reo v er c o nfi r m e d t h e i m pre s s io n t ha t e x cept i n c as e s li k e t h e c h lori d e
o f zi n c wh e n wa ter a ct s c h e m ic a ll y u p o n t h e su b s t an ce l ittle or n o wa ter
i s ret a i n e d b y m o s t fus e d sa lt s I f a r g e n tic n itr a te wh ic h a t 2 0 0 i s mi s ci
ble w it h wa ter i n a ll pro portio ns s et s f ree s o n e a rl y a ll t ha t it po ss e ss e s
i n a c u rre n t o f d r y a ir a t t h i s te m per a t u re it i s mu ch m o re li k el y t ha t
ot h er sa lt s fu s i ng a t a h i gh er te m per a t u re and po ss e s s i ng a le ss a ttr a ctio n
f or wa ter sh o u l d be f ree f ro m it af t e r fu s io n Th i s i s a re assu ri ng co n
v i ct i o n w ell w orth t h e tro u ble s pe n t u po n t h e p o i n t
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T H E P U RI T Y O F T H E F U S E D A RGEN T I C N I T R A T E
61
.
A tte n tio n was n o w d irecte d to ot h er f orei gn su b s t an ce s be s i d e s wa ter
and a i r wh ic h m i gh t be pre s e n t i n t h e syn t h etic a r g e n tic n itr a te F u rt h er
c a re fu l i nve s ti ga tio n was n ee d e d to sh o w t ha t a ll t h e s il v er wa s co m bi n e d
as n itr a te and t ha t n o ot h er i m p u ritie s w ere co n ce a le d i n t h e sa lt Th e
p u re pe a rl y wh ite n e s s o f t h e col d fu s e d ma teri a l p recl u d e d t h e po ss ibilit y
o f t h ere hav i n g bee n a tr a ce o f re du ctio n to m et a llic s il v er Th e sa lt w a s
s ol u ble i n p u re wa ter w it h o u t re s i du e or t u rbi d it y and ma i n t a i n e d i ts
cle a r n e s s wh e n d il u te d to ha l f or qua rter n or ma l ; h e n ce o x i d e and ha lo g e n
sa lt s mu s t hav e bee n a b s e n t Th e o n l y ot h er li k el y i m p u rit y s ee m e d t o be
amm o n i um sa lt s n itrite and e x ce ss o f n itric a ci d O f t h e s e po ss ibilitie s
S t as t h o ugh t o n l y o f t h e likeli h oo d o f t h e pre s e n ce o f f ree a ci d ; b u t e a ch
w a s c a re fu ll y co ns i d ere d i n the pre s e n t w or k
I t i s kn o wn t ha t copper d i ss ol v i n g i n n itric a ci d f or ms percepti b le quan
titie s o f amm o n ic n itr a te A pp a re n tl y n o s i m il a r re a ctio n h a s b ee n n ote d
w ith s il v er and f ro m an electroche m ic a l s t and poi n t it s ee m e d un likel y
m oreo v er amm o n i c n itr a te i f pre s e n t w o u l d prob a bl y be f or the m o s t p a r t
d eco m po s e d b y the ho u r s fu s io n o f the s il v er sa lt N e v ert h ele ss t h or
N e s s ler s ol u tio n i s the m o s t
ou
gh n es s d e mand e d e v i d e n ce o n thi s poi n t
co nv e n ie n t f or thi s te s t b u t s il v er mu s t fi r s t b e precipit a te d f ro m s ol u tio n
i n the da rk L i gh t ge n er a te s chlori n e wh ich i n ter f ere s w ith the te s t
In or d er to prep a re f or thi s s e a rc h f or amm o n i a t h e syn t h eti c n itr a t e
o f s il v er re su lti n g f ro m s e v er a l e x peri m e n t s w a s sha ke n w ith a s li gh t e x
ce ss o f s t anda r d p u re s o d ic chlori d e un til the su per na t an t li qu i d w a s cle a r ;
an d pl a ce d i n a co m p a ri s o n
th e l a tter w a s d ec an te d mad e u p to 5 0 cc
c y li nd er T h e s o d ic chlori d e g av e n o te s t w ith N e ss ler s ol u tio n
T h e c y li nd er fu ll o f li qu i d prep a re d f ro m t h e a r g e n tic n itr a te w a s fina lly
te s te d b y co m p a ri s o n w ith other c y li nd er s co n t a i n i n g kn o wn tr a ce s o f a m
m o n i c n itr a te m i x e d w ith s o d ic n itr a te i n co n ce n tr a tio n e qua l to th a t e x i s t
i n g i n the a ct ua l d eter m i na tio n T h e s o d ic n itr a te h ad b ee n s e v er a l ti m e s
recr ys t a llize d w ith ce n tri fu ga l d r a i n i n g and w a s S h o wn to b e f ree f ro m
am m o n i a I n thi s w ay the f ollo w i n g re su lt s w ere a tt a i n e d : S yn the s i s 1 2
m g o f amm o n ic n itr a te syn t h e s i s 1 3
mg
w a s f o u nd to co n t a i n
an d syn the s i s 1 4
mg ; i n a ll
gr am s o f a rge n tic n itr a te w ere
pro v e d to co n t a i n n o m ore th an
g r am o f amm o n ic n itr a te — le s s
th an o n e t w o tho u sand th o f 1 per ce n t T he s o u rce o f thi s am m o n i a w a s
n ot d eterm i n e d ; it m i ght h av e co m e f ro m the re du ctio n o f n itric a ci d or
f ro m the l a rge v ol u m e o f a ir u s e d i n e va por a ti ng t h e a rge n tic n itr a t e
T he o n l y po ss i b le pl a ce w here it co u l d h av e e n tere d w it h the re a ge n t s
u s e d i n the te s t w a s i n the s o d i c ch lori d e s ol u tio n ; thi s w a s i nd ee d te s te d
w ith n eg a ti v e re su lt s b u t N e ss ler s re a ge n t i s n ot v er y s e ns iti v e i n th e
pre s e n ce o f chlori d e and a tr a ce o f amm o n i a m i ght h av e el u d e d d etectio n
I f the am o un t f o und h ad b ee n l a r g er m ore ti m e w o u l d h av e b ee n Spe n t
u po n the ma tter and a sam ple o f the a r g e n ti c n itr a te o fte n recr ys t a llize d
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62
TH E Q
U A N T I T A T I V E S YN T H E SIS
OF
AR GEN T I C N I T RAT E
E TC
,
.
i n an a t m o s p h ere f ree f ro m am m o n i a w o u l d hav e bee n u s e d i n a bl an k
e x peri m e n t f or co m p a ri s o n ; b u t w it h su c h a sm a ll tr a ce o f i m p u rit y t h i s
was n ot w o rt h wh ile
In s u m m i n g u p t h e re su lt s o f t h e te s t f o r amm on i a t h e am o un t Sh o u l d
be c a lc u l a te d f o r t h e quan tit y o f a r g e n tic n itr a te pro du ce d f ro m
g r a m s o f s il v er Thus it i s f o und t ha t
g r a m s o f fu s e d a r g e n tic
n itr a te co u l d n o t hav e c o n t a i n e d o v er
g ram o f am m o n ic n itr a t e
Th e n e x t i m p u rit y to be s t u d ie d n itr o u s a ci d was s o ugh t b y m e ans o f
su lp han ilic a ci d and na p h t hy l am i n e hyd ro c h l o ri d e Th e s e w ere pro v e d
w it h a s t anda r d n itrite s o l u tio n o f wh ic h 1 liter c o n t a i n e d
g ram o f
n itr o g e n T o i nsu re p a ra ll e l c o nd itio ns i n te s ti ng b y co m p a ri s o n p u re s i l
v er n itr a te was prep a re d w it h s o m e c a re I t was t h rice recr ys t a llize d
f r o m n itric a ci d w it h ce n tri fuga l tre a t m e n t fus e d i n porcel a i n t h e n r e cr y s
t a l l i z e d t h ree ti m e s m ore f ro m t h e p u re s t wa ter i n pl a ti nu m w it h ce n t r i f
uga l d r a i n i ng as be f ore Th e S peci m e ns o f fus e d a r ge n tic n itr a te re su lt
i n g f ro m quan tit a ti v e d eter m i na tio ns w ere d i ss ol v e d i n kn own a m o un t s
o f wa ter and co m p a ri s o n s ol u tio ns o f e qu a l co n ce n tr a tio n prep a re d Th e
c rys t a llize d S il v er n itra te gav e n o tr a ce o f pi nk c o lor w it h t h e re ag e n t s
A f re sh S ol u tio n to w hic h
cc o f n itrite s ol u tio n
mg ) had bee n
add e d gav e a pro n o un ce d color wh ile d eter m i na tio ns 2 3 and 1 1 a ll
g av e a mu c h fa i n ter b a rel y v i s ible color ; h e n ce it was perm i ss ible to co n
cl u
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to u r n e s ol and f o und t h e m a l ka
s ol u tio ns o f h i s fus e d s il v er n itr a te w it h
li n e r a t h er t han a ci d Th i s a l ka li may hav e co m e f ro m h i s gl as s v e s s el s
W e u s e d m et hy l or ang e a m o re S e ns iti v e i nd ic a tor and n ote d t ha t t h e
p u re s t cr ys t a llize d n e u tr a l s peci m e ns and t h e fu s e d sa lt a li k e gav e e qua ll y
p ro n o un ce d a ci d re a ctio ns i n s o l u tio n Th e col o r was n ot m o d i fi e d b y t h e
add itio n o f ha l f a m illi g r am o f n itri c a ci d ; t h ere f ore t h e e qua lit y i n color
d oe s n o t d i s pro v e t h e pre s e n ce o f f ree a ci d i n o u r fus e d pro du ct
D il u te
s o d ic hyd ro x i d e f ree d f ro m c a rbo na te b y b a ri c hyd ro x i d e t h re w d o wn a
p recipit a te w it h o u t c hang i ng t h e pi nk c o l o r H e n ce t h e i nd ic a tor w a s d i s
c a r d e d and the i nv e s ti ga ti o n c o n ti nu e d w it h t h e n ep h elo m eter
Th e te s t f or a ci d w it h the h elp o f th i s i n s tr um e n t was co ndu cte d b y add
i ng a v e ry d il u te s t anda r d c au s tic a l ka li n e s ol u ti o n to t h e s ol u tio n to be
te s te d and b y ob s erv i ng i f t h i s add itio n c au s e d a per man e n t clo u d
P reli m i na r y tri a l s w ere n ece ssa ry i n t h e fi r s t pl a ce i n or d er to d eter m i n e
t h e co nd itio ns be s t su ite d f or a cc u r a c y I t was f o und t ha t a co n ce n tr a tio n
o f n itr a te n o s tro nger t han 4 g rams i n
liter was be s t ada pte d to t h i s
w or k as a r ge n tic hyd ro x i d e i s d i s ti n ctl y s ol u ble i n d o u ble thi s co n ce n tr a
ti o n o f a r g e n tic n itr a te On t h e ot h er hand a r g e n tic hyd ro x i d e pr e ci pi
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P UR I T Y
TH E
O F TH E F U S
ED AR GEN T I C N I T RAT E
.
b y s o m e wha t c o n ce n tr a te d a l ka li d oe s n ot qu ic k l y re d i ss o l v e i n an
e q u i va le n t quan tit y o f n itric a ci d m i x e d w it h t h e d il u te a r g e n tic s ol u tio n
I t w a s f o und t ha t e v e n t h e p recipit a te c au s e d b y
m 1 o f a t w o hun
d r e d th n o r ma l s ol u tio n may pro du ce a fa i rl y per m an e n t clo u d i n S pite o f
t h e pre s e n ce o f an e x ce s s o f
g r am o f n itric a ci d e n o ugh to d i s
s ol v e i t S till m ore d il u te s ol u tio ns be hav e d mu c h m ore sa ti s fa ct o ril y
h o w e v er A m illiliter o f a t w o t h o u sand t h n o rma l c au s tic s ol u tio n ( e qu i v
a l e n t to
g r am o f n itric a ci d ) add e d w it h c o ns t an t s ti rri ng to t h e
p u re s t anda r d a r g e n tic n itr a te f o rm e d a clo u d e as il y s ee n i n t h e n ep h
e l om e te r
I n c as e
g ram o f n itri c a ci d had bee n i n tro du ce d
be f ore add i ng a l ka li n o p recipit a te wa s f or m e d und er t h e sam e co nd itio ns
H e n ce und er t h e s e circ ums t an ce s t h e te s t a tt a i n e d a d e g ree o f s e ns iti v e
n e s s su ite d to t h e c as e i n hand
I n t h i s way it w a s f o und t ha t t h e a r ge n ti c n itr a te re ma i n i ng f ro m syn
t h e s i s 1 1 gav e a d i s ti n ct op a le s ce n ce w it h t h e add itio n o f
g r am o f
s o d ic hyd ro x i d e and an ob v io u s clo u d w it h
g r am H e n ce it wa s
co n cl u d e d t ha t a r g e n ti c n itr a te fu s e d i n a s tre am o f p u re a i r f or o n e ho u r
co n t a i ns n o w ei gha ble e x ce s s o f n itric a ci d
Th e va rio u s sus pecte d i m p u ritie s hav i n g t hu s b ee n du l y s o ugh t it i s
i ns tr u cti v e and i n tere s ti ng to t a b u l a te the re su lt s T he s e a re as f ollo w s :
tate d
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We i gh t o f f u s e d A gNO
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the su btr a cti v e correctio ns g i v e n i n the a bo v e t a ble a re max i mum
va l u e s the w ei gh t o f a rge n tic n itr a te i n qu e s tio n c an ha r d l y b e lo w e r t han
thi s va l u e
O n t h e ot h er h and it c an h a r d l y b e hi gher th an t h e
un correcte d va l u e
T hu s t w o li m it s a re s e t v er y n e a r toget h er
bet we e n w hich the tr u e va l u e mu s t lie O b v io u s l y f or t h e p re s e n t o n e
c an n ot g o v ery fa r as tr ay i n a ccepti n g the m e an va l u e
and thi s
va l u e w ill be u s e d i n the follo w i n g d i s c u ss io n
As
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TH E
64
FI NAL
THE
QU A N T I T A T I V E S " N T HE S I S
RES
O F A RGEN T I C N I TRAT E
,
UL T A ND I TS REL A T IO N S
WEI G H TS O F N I TRO GE N
ETC
T O THE V A L UES
S I LVER
A ND
OF
.
A TO M I C
.
Th e co n cl us io n re a che d b y t h e f ore goi ng s erie s o f e x peri m e n t s i s t ha t
p a rt s o f S il v e r y iel d v er y n e a rl y
p a rt s o f a r g e n ti c n itr a te
A m o ng ot h er e x peri m e n ter s P e nny f o und
Ma ri gna c f o und
S t as f o und
i n o n e s erie s o f s e v e n d eter m i na tio ns and
i n an ot h er o f t w o and H a r d i n f o und
F ro m t h e s e ol d er
fi gu re s b y an i n tere s ti n g coi n ci d e n ce Cl a r k e c a lc u l a te d e xa ctl y t h e va l u e
1
f o und i n t h e pre s e n t re s e a rc h Th i s coi n ci d e n ce i s to be a ttrib u te d n ot
s o mu c h to t h e e f fi c a c y o f t h e m et h o d o f c a lc u l a tio n a s to t h e fa ct t ha t i n
t h i s c as e t h e i m p u ritie s i n t h e s il v er ha ppe n e d to b a l an ce e xa ctl y t h e i m
p u ritie s i n t h e a r g e n tic n itra te A t fi r s t S i ght it i s i n co m pre h e ns i b le h o w
S t as w or k i ng w it h s li gh tl y i m p u re s il v er co u l d hav e obt a i n e d any re su lt s
higher tha n the tru e va l u e ; b u t it mu s t be re m e m bere d t ha t h i s n itra te w a s
fus e d i n a gl as s v e ss el w hich mu s t hav e bee n a tt a cke d b y t h e s tro ng l y
a ci d n itr a te a t
C o ns t an c y i n the w ei g ht o f the v e ss el w o u l d be n o
e v i d e n ce o f a b s e n ce o f a ctio n f or s il v er m i gh t p a rtl y t ak e i n t h e g l ass th e
pl a ce o f t h e s o d i um t a ke n f ro m it T h u s a ga i n i n w ei ght du e to s o d ic
n itr a te m ight b e a cco m p an ie d w ith n o co ns i d er a b le lo ss o f w eight o f the
v e s s el In fav or o f t h i s h y pot h e s i s i s t h e fa ct t ha t S t as s re su lt s s te ad il y
d ecre as e d i n e a c h s erie s a s h e procee d e d w it h t h e w or k ; the flas k s ee m s to
h av e bee n le s s and le ss sus ceptible to a tt a c k as i s re as o na ble I f t h e l as t
t w o d ete r m i na tio ns o f the fi r s t s erie s a re t ak e n a s the m o s t n e a rl y f ree f ro m
thi s c au s e o f error the num ber
obt a i n e d f ro m the m sh o u l d fu r n i s h
b y co m p a ri s o n w ith o u r num ber s o m e cl u e to the am o un t o f gas eo us i m
p u rit y i n S t as s s il v er T h u s it a ppe a r s th a t h i s s il v er mu s t h av e co n t a i n e d
n e a rl y
per ce n t o f i m p u rit y p ro b a b l y m ore i f it i s co ns i d ere d th a t
t h e flas k w as s till n ot w holl y re s i s t an t —a co n cl u s io n n ot v e r y d i ff ere n t
f ro m th a t re a che d b y R ich a r ds and W ell s
S pec u l a tio ns o f t h i s ki nd co n ce r n i n g ol d er w ork a re r a ther a th an kle s s
t as k h o w e v er ; t h ere i s usua ll y too mu c h th a t i s d o u bt fu l to a llo w the m to
s e rv e a v er y va l ua ble p u rpo s e Th e o n l y ob j ect i n p u r su i n g the re v ie w a t
a ll i s i n or d er to assu re o n e s s el f t ha t n o re a l i n co ns i s te n c y e x i s t s i n the
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Reca l cu l a t i on
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IV
WE IG H T O F A RG ENTI C S U L PH A TE
ATO MI C WEI G H T O F S UL PH U R
TH E M O L EC U LA R
TH E
THE O D O R E
C O NTR I B UT I O NS
WI LL IA M
F RO M TH E
RI C H A R D S
A ND
C H EM I C A L L A B O R ATO R"
G R I NN E LL
OF
J O N ES
H A RV A RD C O LL EG E
AND
WE IGHT 0 F ARGE NTIC SULPHATE
ATOMIC WE IGHT DE SULPHUR
THE MOLE CULAR
AND THE
.
I N TRO DUCTIO N
.
T he a to m ic w eight o f su lphh u r h a s bee n i nv e s ti ga te d b y many exper i
m e n ter s ; b u t a s w ill b e s ee n tt hh e re su lt s a re f a r f ro m co n cor dan t A
b rie f re v ie w o f the s e i nv e s tiga tio ns f or ms the m o s t a ppropri a te i n trod uc
tio n to the pre s e n t o n e T he va l u e s i n the f ollo w i n g li s t hav e b ee n rec a l
l a te d w ith m o d er n fi g u re s f or the other a to m ic w eight s i nv ol v e d :
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T he w ork o f the pre d ece ss or s o f S t a s
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and d oe s n ot m erit d et a ile d critici sm ; i n rece n t ti m e s the a to m ic w eight
o f su lp hu r h a s re s te d c h ie fly u po n the e x peri m e n t s o f the fam o us Belgi an
S t as co nv e rte d s il v er i n to it s s u lphi d e b y he a ti ng it i n a c u rre n t o f s ul
ph u r va por o r h yd ric su lp h i d e ; b u t b ec aus e he d i d n ot k n o w the pr eca u
3
tio n s n ece s sa ry f or p rep a ri n g per fectl y p u re s il v er it i s e v i d e n t th a t al l
o f h i s w ork i n w hich s il v er w a s w eighe d n ee ds re v i s io n S t as a l s o re du ce d
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M O LE C UL A R W E I GH T O F A RGEN T I C S ULP H A T E
70
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.
d i d n ot t ak e t h e v er y i m port an t prec a u tio n o f fus i ng t h e su lp ha te be f ore
w ei gh i ng ; and m ore o v er t h e p o ss ibilit y t ha t t h e re du ce d S il v er m i gh t con
t a i n a r g e n tic s u lp h i d e o r su lp ha te was b y n o m e ans e x cl u d e d
A brie f re v ie w o f s u b s e qu e n t w or k m a y n ot be o u t o f pl a ce a lt h o ugh i t
i s O f a d i f f ere n t or d er O f preci s io n C o o k e re du ce d a r g e n ti c su lp h i d e i n a
c u rre n t o f hyd ro g e n and c o n cl u d e d t ha t t h e a to m i c w ei gh t o f su lp hu r
mu s t lie bet w ee n t h e li m it s
and
I n sum m i ng u p h i s re su lt s
“
h e s t a te d t ha t t h i s i s e qu i va le n t to co nfi r m i ng t h e a ccepte d va l u e o f
t h i s co ns t an t s o fa r as any e x peri m e n t s o n a s c a le le ss e x te ns i v e t han t h o s e
”
o f S t as c an be o f va l u e to t h i s e nd
Th e d eterm i na tio n o f t h e a to m ic w ei gh t o f su lp hu r b y R ic ha r ds was
mad e i n ci d e n t a ll y i n h i s w o r k on t h e a to m ic w ei gh t o f copper Th e r a tio
I f s o d i um i s t ak e n a s
Na C O sg Na S O gav e as a re su lt S
i ns te ad o f
t h e re su lt becom e s S
N O v e r y g re a t
co nfid e n ce was pl a ce d i n t h e s e re su lt s a t t h e ti m e as i s Sh o wn b y t h e f ol
“
l o w i ng s e n te n ce :
Th e re su lt s a re ha r d l y c a p a ble o f d eci d i n g t h e pre s e n t
3
u n ce rt a i n t y i n t h e a to m i c w ei gh t o f su lp hu r
I t i s prob a ble t ha t t h e
re su lt i s too lo w as n o proo f co u l d be Obt a i n e d o f t h e t h oro ugh d e s i cca
tio n o f t h e s o d ic c a rbo na te
V er y rece n tl y num ero u s a to m ic w ei gh t d eter m i na tio ns h av e a ppe a re d
d epe nd i n g o n a p u rel y p hys ic a l m et h o d b as e d o n t h e assump ti o n t ha t
A v o gad ro s hy pot h e s i s and th e S i m ple gas l aw P V R T i s s trictl y tr u e
f or gas e s wh e n i nfin itel y e x p and e d S i n ce it i s i m po ss ible to d eter m i n e th e
r a tio s o f t h e d e n s itie s o f gas e s w it h su f fi cie n t a cc u r a c y a t v er y lo w pre s
su re s i t i s n ece ssa r y to d eterm i n e t h i s r a tio und er n or ma l co nd itio ns and
a ppl y a d i f f ere n t correctio n i n e a c h c as e d epe nd i ng o n t h e d e v i a tio n o f
t h e ga s f ro m t h e s i m ple gas l aw I t i s prob a ble t ha t t h e r a tio o f t h e d e n
s itie s c an be and i n m o s t c as e s ha s bee n d eter m i n e d w it h su ffi cie n t per
ce n t ag e a cc u ra c y On t h e ot h er h and t h e correctio n i s hy pothetic a l
and mu c h le s s ce rt a i n ; and a ccor d i ng l y t h e m et h o d has b u t little va l u e
wh e n t h e corr ectio n i s l a rg e
“
A ccor d i ng to L e du c t h e r a tio bet w ee n t h e d e ns itie s o f su lp hu r d io x i d e
and o xyg e n i s
I f n o correctio n i s a pplie d f or t h e i m per f ectio n O f
t h e gas e s t h i s va l u e le ads to
f or t h e a to m ic w ei gh t o f su lp hu r Th e
correctio n i n t h i s c as e i s unu su a ll y l a r g e and th ere f ore mu s t be k n o wn
w it h a h i gh perce n t ag e a cc u r a c y i f t h e re su lt i s to hav e any va l u e as
a d eter m i na tio n o f a to m ic w ei gh t s T h e f ollo w i ng a re t h e ge n er a l m et h
o ds o f c a lc u l a ti ng t h e correctio n b u t n o n e s ee m s to be o f su ffi cie n t va l u e
f or t h e pre s e n t c as e
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I N T ROD U C T IO N
71
.
Th e fi r s t c a lle d t h e m et h o d o f corre s po nd i ng s t a te s was d e v elope d
f or t hi s p u rpo s e b y L e du c
I t d epe nds o n t h e as sum ptio n o f van d er
W aa l s t ha t t w o gas e s a re i n corre s po nd i ng s t a te s and d e v i a te e qua ll y f r o m
t h e hy pot h etic a l per f ect gas i f t h eir tem per a t u re s and pre s su re s a re e q ua l
mu ltiple s or s ub —
mu ltiple s o f t h ei r critic a l te m per a t u re s and pre ssu re s
re s pecti v el y In c a lc u l a ti ng t h e correcti ng fa ctor t h e co m pre s s ibilit y and
2
L e du c b y t h i s m et h o d obt a i n e d
critic a l co ns t an t s a re u s e d
a s t h e m olec u l a r w ei gh t o f su lp hu r d io x i d e an d
as t h e m olec u l a r
w ei gh t o f hyd r o g e n su lp h i d e and h e n ce f ro m bot h S
Th e s eco nd m et h o d i s t h e m et h o d o f critic a l co ns t an t s as d e v elope d
3
b y G uy e Th e correctio n i s c a lc u l a te d b y t h e us e o f van d er Wa a l s s e qu a
tio n t h e q uan titie s a and I) bei ng c a lc u l a te d f ro m t h e critic a l co ns t an t s o f
t h e gas e s und er co ns i d er a ti o n In a c o m plic a te d mann er G uy e a pplie d a
correctio n to t h e quan titie s a and b o f van d er Wa a l s s e q ua tio n bec au s e
4
t h e y a ppe a r to va r y S li gh tl y w it h t h e te m per a t u re and t h e pre ssu re and
i n t h i s way wa s Obt a i n e d t h e va l u e
a s t h e m olec u l a r w ei gh t o f su l
p hu r d io x i d e ; h e n ce S
Th e t h i r d m et h o d i s c a lle d th e m et h o d o f li mi ti ng d e ns it y
I t was
5
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?
and J a q ue r o d
I t d epe nds o n t h e e x peri m e n t a l d eter m i na tio n o f t h e com
p r e s s i b i l i t i e s o f gas e s a t pre ssu re s i n t h e n ei g hbor h oo d o f o n e a t m o s p h ere
“
”
B y an e x tr a p o l a tio n t h e li m iti ng r a tio o f t h e d e ns itie s a t v er y lo w pre s
su re s c an be c a lc u l a te d Th i s m et h o d has re a che d it s g re a te s t per f ectio n
i n th e hands o f L or d R ay lei gh wh o has sh o wn t ha t f or the per man e n t
gas e s t h e d e v i a tio n f ro m B o y le s l aw o n l y va rie s S li gh tl y w it h t h e pre ssu re
and t h ere f ore t h e e x tra pol a tio n i s fa irl y saf e Th i s p hys ic a l m et h o d has
bee n a pplie d w it h t h e g re a te s t su cce ss to t h e c as e s o f hyd ro g e n c a rbo n
and e s peci a ll y n itro g e n bec au s e i n t h e s e c as e s t h e correctio n i s c o m p a r
a t i v e l y s m a ll
H ere a l s o h o w e v er t h e a pplic a tio n to su lp hu r i s fa r le ss
sa ti s fa ctor y I t i s to be re g rette d t ha t L or d R a y l e i gh s w ork d i d n ot
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M O LE C UL A R WE I GH T O F A RGEN T I C S ULP H A T E
72
E TC
,
.
assum ptio n th a t t h e d e v i a tio ns f ro m Bo y le s l aw d i m i n i s h a s the pre ssu re i s
lo w ere d Th e y obt a i n e d
as t h e a to m ic w ei ght o f su lp hu r A f ter
wa r ds I a que r od and S c h e u er d eterm i n e d t h e co m pre ss ibilit y o f su lph u r
d io x i d e t h r o ugh t h e r ang e s 4 0 0 to 80 0 mm and 2 0 0 to 4 0 0 mm b y a
m eth o d S i m il a r to L or d Ra y l e i gh s Th e y f o und as was to be e x pecte d
t ha t th e d e v i a tio n f ro m B o y le s l aw was sma ller a t t h e l o w er pre ssu re
N e v ert h ele s s i n c a lc u l a ti n g t h e m olec u l a r w eig h t o f su lp hu r d io x i d e t h e y
as sum e d t ha t t h e d e v i a tio n f ro m B o y le s l aw per ce n ti m eter o f pre s su re
b et w ee n 0 and 7 60 mm w a s the sam e a s bet w ee n 4 0 0 and 80 0 mm T he y
Obt a i n e d
f or su lp hu r d io x i d e and h e n ce S
I f thei r m e as
ure m en t o f t h e co m pre s s ibilit y t h ro ug h the r ang e 20 0 to 4 0 0 mm i s u s e d
t h e re su lt beco m e s
and it s ee ms prob a ble t ha t y et a h i gher va l u e
i s t h e tr u e o u tco m e o f t h eir e x peri m e n t s T he s e d i f f ere n t co n cl us io ns e m
ph a s i z e t h e un cert a i n t y o f t h e m e th o d
P rob abl y t h e ads orptio n o f su lp hu ro u s o x i d e and h yd ric su lp h i d e o n the
g l ass o f t h e co n t a i n i n g g lobe s i n tro du ce s an error i n bot h the d e ns it y and
co m pre ss ibilit y d eterm i na tio ns and he n ce i n fa ct s to wh ich the as sum ptio n
a bo v e m e n tio n e d a re a pplie d Th i s po ss ibilit y o f ads orptio n s ee ms to hav e
b ee n n ot su ffi cie n tl y h ee d e d b y any o f t h e e x peri m e n ter s o n su lph u r co m
po unds I t adds y et an ot h er un cert a i n t y to t h e re su lt s
T he u p s hot o f the s e co ns i d er a tio ns i s the co n cl us io n th a t n o n e o f t h e
w ork h ereto f ore d o n e u po n t h e a to m ic w ei gh t o f su lp hu r d eci d e s it s va l u e
H e n ce f u rt h er i nv e s ti ga tio n i s i m per a ti v e
Th e p roble m f or co m plete
s ol u tio n mu s t b e a pp ro a c h e d f ro m many s i d e s and t h e w ork mu s t i nv ol v e
many co m po u nds o f su lp hu r T he f ollo w i n g co n trib u tio n d e s cribe s o n e
s ectio n o f a co m pre h e ns i v e pro g r am b y w hich it i s hope d the q u e s tio n may
be answ ere d
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P REL
I M I N A R"
I MEN TS
E"P ER
.
ui tab l e s t a rti n g poi n t
f or t h e pres e n t i nv e s ti ga tio n bec au s e it s ee m e d prob a ble th a t thi s sa lt
co u l d be prep a re d i n a p u re co nd itio n and a cc u r a tel y ana l y ze d A fu rt h er
re as o n f or s t udy i ng a r g e ntic su lp ha te lie s i n t h e po ss ibilit y o f l a ter co m
bi n i n g t h e re su lt s w it h s o m e r a tio i nv ol v i ng t h e su lp h i d e and t hus fu r
n i s h i n g e v i d e n ce o n t h e e v e n m ore i m po rt an t q u e s tio n as to the a to m ic
w ei gh t o f S il v er B a l an ce d aga i ns t t h e advan t age s i s the d i sadvan t ag e
t ha t o n l y a bo u t 1 0 per ce n t o f it s w ei gh t i s su lph u r c aus i n g t h e e xpe r i
m e n t a l error s to be g re a tl y mu ltiplie d i n t h e c a lc u l a tio ns ; b u t t h e a d v a n
t age s m ore t han o u t w eigh the d i sadvan t ag e
A te n t a ti v e preli m i na r y pl an o f Oper a tio ns was to fus e a r g e n tic su lph a te
i n a pl a ti num cr u cible d i ss ol v e it precipit a te a s c h lori d e and collect and
w ei g h t h e precipit a te Th i s pl an was th wa rte d b y num ero u s ob s t a cle s
T he su lph a te o f s il v er was s electe d as the
m os t
-
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,
.
.
,
.
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M O LE C UL AR WE I GH T O F AR GE N T I C S ULP H A T E
74
E TC
,
.
Th e m e th o d o f prep a ri ng t h e m a teri a l s t h e Sha pe and na t u re o f t h e
a pp a r a t u s and m any o f t h e p rec au ti o n s a n d d eta il s o f man ip u l a tio n w ere
ad opte d on l y a f ter nu m e r ou s preli m i na r y e x p e ri m e n t s A d et a ile d a cco un t
O f t h i s t e n t a ti v e w o r k i s h o w e v er u n n ece ssa r y S i n c e t h e i m p o rt a n t r e su lt s
a re i m p l i e d i n t h e d e s cripti o n O f t h e m et h o d wh ic h wa s fina ll y ad opte d
,
,
.
,
,
,
.
PREP A RATIO N O F PU RE M ATERI A LS
THE
S UL P H U RI C A C ID
.
.
”
Th e be s t co mm erci a l c h e m ic a ll y p u re a ci d was t w ice f ra ctio na ll y d i s
tille d u s i ng a qua rtz c o nd e ns er and a pl a ti num d i s h a s recei v er On l y
t h e m i dd le f r a ctio ns w ere u s e d ; 1 7 g r ams le f t n o v i s ible or w ei gha ble
re s i du e o n e va por a tio n
AR GEN T I C S ULP H A T E
“
.
,
.
.
P u re a rg e n tic c h l o ri d e re s i du e s f r o m pre v i o u s a t om ic w ei gh t i nv e s ti ga
tio ns i n t h i s l a bor a tory w ere re du ce d w i t h i nv ert s uga r and s o d ic hyd r a te
Th e re du ce d S il v er wa s t h o ro ugh l y wa s h e d and d i ss o l v e d i n n itric a ci d ;
and t h e n itra te wa s d il u te d an d fi ltere d I t was e va p o r a te d o n t h e s te am
b a th un til sa t u r a te d and cr ys t a llize d b y add i ng an e qua l v ol u m e o f co n
Th e cr ys t a l s w ere d r a i n e d ce n t r i f u
c e n t r a t e d n itric a ci d and co o li ng
ga ll y a s u sua l
Th e crys t a lliz a tio n f ro m p u re c o n ce n tr a te d n itric a ci d
and ce n tri fuga l d r a i n i ng was repe a te d fiv e ti m e s u s i ng J e na gl ass v e ss el s
I t wa s fina ll y recr ys t a llize d o n ce m ore u s i ng a pl a ti nu m d i sh and re d i s
tille d n itric a ci d Th i s s il v er n itr a te was d i ss ol v e d i n a s m a ll am o un t o f
wa ter i n a pl at i nu m d i s h and an e x ce ss o f t h e p u re s t su lp hu ric a ci d d il u te d
w it h an e qua l v ol u m e o f p u re wa ter was p o u re d i n to it Th e precipit a te d
S il v er su lp ha te was d r a i n e d i n t h e ce n tri fuga l ma c h i n e I t was t h e n d i s
s ol v e d i n h ot c o n ce n tr a te d su lp hu ric a ci d i n a pl a ti nu m d i s h and t h e s ol u
tio n was boile d f or s e v er a l m i nu te s to e x pel n itric a ci d On cooli ng th e
a ci d su lp ha t e cr ys t a llize d i n l a r g e cr y s t a l s Th i s a ci d su lp ha te was v e ry
t h o ro ugh l y wh irle d pl a ce d i n a pl a ti nu m d i sh and tre a te d w it h p u re s t
wa ter H e a t was e v o l v e d and t h e n or m a l su lp ha te crys t a llize d o u t a s a
fin e po wd er Th i s p owd er was wash e d b y d ec an t a tio n w it h t h e p u re s t
wa ter un til t h e wash —
wa ter s w ere n o lo nger a ci d
A ll t h e wa ter u s e d i n
th i s w o r k was p u ri fi e d i n t h e mann er d e s cribe d i n pre v io u s commun i ca
tio ns Du ri ng t h i s wash i ng t h e a cti o n o f li gh t o n t h e w et s il v er su lp ha te
pro du ce s a s li gh t v i o let color Th i s h o w e v er d o e s n o ha r m as any s li gh t
d eco m p o s iti o n i s re m e d ie d du ri ng t h e su b s e qu e n t fus i o n
I t was t h e n
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h rds J A m Ch m S 2 7 1 0 4
U l ss t h i s pr u t i i s t k th s i lv r s u l ph t
th
i —
b th ; i
wh i h
s i t w u l d b i mp ss i b l t l
d f th t u b i t w h i h i t w
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T H E P R EP ARA T IO N O F P U R E M A T E RIA L S
75
.
d rie d as mu c h a s po s s ible i n t h e ce n tri fuga l ma c h i n e and t h e d ry i ng wa s
co m plete d i n an a ir b a t h a t
Th e s e oper a tio ns w ere c a rrie d o u t a s
m u c h as p o ss ible und er t h e protectio n o f a v ery l a r g e i nv erte d funn el and
t h e d i sh was k ept co v ere d w it h a l a r g e wa tc h gl as s to avoi d t h e i n tr o d uc
tio n o f du s t Th i s sam ple was c a lle d A and was us e d i n t h e preli m i na r y
s erie s and i n e x peri m e n t s 4 and 5 o f t h e fina l s erie s o f quan tit a ti v e e xp e r i
ments
S a m ple A was d i s s o l v e d i n co n ce n tr a te d su lp hu ric a ci d boile d cr ys t a l
l i z e d as a ci d su lp ha te b y co o li ng ce n tri fu g a ll y d r a i n e d co nv e rte d i n t o
t h e n or ma l su lp ha te b y add i n g wa ter wash e d and d rie d as be f ore Th i s
sa m ple was c a lle d sa m ple B S i n ce t h e m e an o f t h e re su lt s w it h t h i s sam
ple i s t h e sam e a s t h e m e an o f e x p e ri m e n t s 4 and 5 i n wh ic h sam ple A
wa s u s e d it i s e v i d e n t t ha t t h e b o ili ng o f t h e su lp hu ric a ci d s o l u tio n fol
lo w e d b y a cr ys t a lliz a tio n i n t w o d i ff ere n t cr ys t a lli n e f orm s d i d n o t a f f ec t
t h e re su lt ; t h ere f ore fu rt h er p u ri fi c a tio n s ee m e d unn ece s sa r y
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H Y DRO C H L ORI C
H yd roc h loric
A C ID
.
a ci d wh ic h was o n l y u s e d a s a gas was mad e f ro m tw o
s o u rce s In e x peri m e n t s 5 and 6 t h e hyd roc h l o ric a ci d was mad e b y d rop
pi ng p u re su lp hu ric a ci d o n p u re amm o n i um c h lori d e In t h e ot h er e x
pe r i m e n t s t h e be s t co mm erci a l co n ce n tr a te d hyd roch l o ric a ci d was u s e d
R ic ha r ds and W ell s hav e Sh o wn t ha t t h i s a ci d co n t a i n e d n o ot h er ha lo g e n
or a r s e n ic ; it was t h e re f ore su it a ble f or o u r p u rp o s e
,
,
.
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.
1
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TH E FU S IO N
A RGEN T I C S U LP H A TE
OF
.
M u ch t h o u gh t w a s e x pe nd e d o n t h e d e v i s i ng o f a piece o f a pp a ra t u s
wh ich s ho u l d be su it a ble n ot o n l y f or t h e fu s io n o f a r g e n tic su l ph a te b ut
a l s o f or t h e q uan tit a ti v e co nv er s io n o f t h e su lp ha te i n to t h e c h l o ri d e
F i na ll y t h e s i m ple sym m etric a l t u be sh o wn i n t h e d i ag r a m was f o und to b e
,
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be s t I t wa s t h e o u tco m e o f s e v er a l tri a l s and sugg e s tio ns and co ns i s te d
o f a t h i n c y li nd ric a l t u be o f fu s e d q ua rtz w it h sma ller qua rtz t u be s fus e d
u po n the e nds
Th e t u be was v er y li gh t w ei gh i ng le s s t han 6 g r ams A
v er y fin e pl a ti num w ire w a s w r a ppe d many ti m e s a ro und t h e co ns tricte d
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ara
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k i n d n e ss
To M r
ca t i o n o f
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M O LE C UL A R W E I GH T O F A RGEN T I C S U LP H A T E
76
ETC
,
.
( A ) b y p u lli n g t h i s t h e t u be co u l d be re ad il y rot a te d
b a l an ce i n a h orizo n t a l po s itio n b y m e ans o f a pl a ti num
w ire Th e sam e t u be w a s u s e d t h ro ugh o u t t h e re s e a rc h the c y li nd ric a l
s h a pe g i v i ng it su f fi cie n t s tre n gt h to w it hs t and a ll t h e s tr a i ns to w hic h it
was su b j ecte d
Th e t u be re ma i n e d re ma r ka b l y co ns t an t i n w ei gh t i n s pite o f t h e v er y
v i goro u s t re a tm e n t it recei v e d D u ri ng t h e e n ti re fif tee n e x peri m e n t s t h e
lo s s i n w eigh t was o n l y
mg and du ri ng t h e t w el v e e x peri m e n t s o f
mg
T h i s s li ght lo ss i s p rob a b l y
t h e fina l s erie s the lo s s w a s o n l y
a cco un te d f or b y a s lig h t s ol u bilit y o f t h e q ua rtz i n the co n ce n tr a te d
a mm o n i a or pot ass ic c yan i d e s ol u tio n u s e d to re m o v e t h e a rge n tic chlori d e
a f ter e a c h d eter m i na tio n
Th e su lp ha te o f s il v er prep a re d a s d e s cribe d a b o v e mus t h av e co n t a i n e d
a little i n cl u d e d wa ter and e x ce s s O f su lp hu ric a ci d s i n ce it h ad bee n cr ys
1
Th e o n l y cert a i n m et h o d o f re m o v i ng
ta l l i z e d f ro m an a ci d S ol u tio n
m ot h er li qu or i n cl u d e d w it h i n cr ys t a l s i s to fu s e t h e sa lt T hi s p a rt o f the
p roble m c aus e d co ns i d era ble di fli cul ty f or it was f o und t ha t a r g e n tic s ul
n
h
a
te
d
eco
m
po
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li
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ello
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ro
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p
i n color I n or d er to d ecre as e t h i s t h er ma l d i s s oci a tio n t h e e x peri m e n t
w a s mad e o f fus i ng the sa lt i n a c u rre n t o f d il u te su lph u ri c o x i d e w ith
T he sa lt i s t h e n p u re w hite i n color
c o m plete su cce s s
T he sma ll crys t a l s O f a rg e n tic su lph a te w ere p us he d i n to the t u be w ith
a pl a ti num ro d and t h e na rro w e nds w ere f ree d f ro m loo s el y adh eri ng
a r g e n tic su lp ha te b y m e ans o f a cle an f e a t h er tip w hich h ad bee n pre v io u s l y
wash e d w it h a lco h ol and et h e r to f ree it f ro m g re as e Th e t u be w a s s u
p
porte d o n hoo ks o f ha r d gl ass i n f ro n t o f t h e a pp a r a t u s f o r d eli v eri n g
s u lp hu r trio x i d e
T h e v er y fin e pl a ti num w ire n ee d e d f or rot a ti ng it h ad
bee n w o und a ro und t h e t u be i n th e fi r s t pl a ce
Th e a pp a r a t u s f or d eli v eri n g a c u rre n t O f p u re d r y a ir or su lph u r tri
o x i d e or hy d ric chlori d e i s sh o wn d i a g r a m a ti ca l l y i n figu re 4
A cur
re n t o f a ir was fi r s t d ri v e n o v er re d h ot copper o x i d e ( A ) to re m o v e or
a
n
i
B
ma
tter
and
su
b
s
e
q
u
e
n
tl
y
t
h
ro
ugh
an
E
mm
erli
n
g
to
w
er
c
(
) co n
g
t a i n i ng be ads m oi s te n e d w it h a s tro ng c au s tic pot ash s ol u tio n Th i s to w er
w a s clo s e d b y a r u bber s topper a t t h e top wh ic h i n tro du ce d n o i m p u rit y
s i n ce n ot h i ng b u t p u re a ir p ass e d o v er it F ro m t h i s poi n t h o w e v er t h e
A ll s topcock s
a pp a r a t u s co n t a i n e d n o r u bber co nn ecti o ns or s topper s
w ere l u bric a te d w it h p h o s p h oric or su lph u ric a ci d
T he a i r was d rie d b y p ass i ng t h ro ugh t w o E mm erli ng to w er s ( C and D )
co nt a i n i ng be ads m oi s te n e d w ith co n ce n tr a te d su lph u ric a ci d T h e c u r
p ortio n o f the t u be
I t w a s h un g o n t h e
.
,
.
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h ds P
Ri c
ar
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.
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.
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.
S oc , 4 2 , 2 8
.
T H E F U SIO N O F
AR
GEN T I C S UL P H A T E
77
.
re n t o f a i r co u l d t h e n be either u s e d i n a p u re d r y s t a te b y p as s i n g throu gh
L or F or el s e c ha r g e d w ith su lph u r trio x i d e b y b u bbli ng t w ice t h ro ug h
f um i n g su lp hu ric a ci d i n the b ottle E T hi s a ci d was kept sa t u r a te d b y
an e x ce s s o f s oli d su lph u r trio x i d e A c u rre n t o f a i r m i x e d w ith any
d e s ire d proportio n o f su lph u r trio x i d e wa s th u s d eli v ere d thro u gh G i n to
t h e q ua rtz t u b e H T he d eli v ery t u be ( G ) and the q ua rtz t u b e ( H )
to u c h e d e a ch other b u t n o a tte m pt wa s mad e to s ec u re a ti ght j oi n t
,
.
.
.
.
,
Fi g 4
.
.
—A pp a a tus f
r
or
de li ve
ri n g a ppropri te g a ses i nto
a
the q
u a tz t u bes
r
.
T he a r g e n tic su lph a te co n t a i n e d i n the qua rtz t u b e was the n fu s e d
a fi s h t a il B u ns e n b u r n er hel d i n t h e h and A re d he a t i s re qu i re d W he n
-
.
.
a ll o f the su lph a te w a s fu s e d the s topcock ( P ) d eli v eri n g su lp h u r trio x i d e
A s s oo n as
wa s clo s e d and a r a pi d c u rre n t o f a i r w a s adm itte d thro u g h F
the fum e s o f su lph u ri c a ci d co u l d n o logger b e s ee n e s c a pi n g f ro m the e nd
o f the qua rtz t u be the flam e w a s re m o v e d and the t u b e w a s Slo w l y rot a te d
b y d r aw i n g o u t t h e pl a ti num w i re w r a ppe d a ro un d o n e e nd T hi s c aus e s
the a rge n tic su lp ha te to s oli d i fy i n a t h i n sh eet a ro und the t u b e U n le s s
c a re i s t ake n to keep t h e sa lt a t le as t 1 c m d i s t an t f ro m either o f the e nd
t u be s d i ffi c u lt y i s e x perie n ce d du ri n g t h e co nv er s io n i n to chlori d e
T he fina l s oli d i fi c a tio n i n the c u rre n t o f p u re d ry a i r w as c a rrie d o u t
v e ry r a pi d l y i n or d er to av oi d d eco m po s itio n and o b t a i n a per fectl y w hit e
‘
,
.
,
.
.
.
.
,
,
M O LE C UL A R WE I GH T O F
78
AR
GEN T I C S ULP H A T E
,
E TC
.
sam ple I f t h e a rg e n tic su lp ha te w a s k ept fu s e d 1 0 or 1 5 s eco nds too lo n g
a f ter t h e su lp hu r tri o x i d e c u rre n t was s toppe d a y ello w i sh b ro wn p ro du ct
was obt a i n e d Th i s i nd ic a te s t ha t t h e sa lt co n t a i n e d eit h er m et a llic s il v er
1
o r a rg e n tic su lp h i d e R ic ha r ds W ell s and F o rbe s hav e Sh o wn t ha t a
s li gh t d i s color a tio n o f a fus e d s il v er sa lt i s a v er y d elic a te te s t f or i m
p u rit y Th e lo s s O f w ei gh t du e to t h i s d i s color a tio n was v e ry s li gh t a s
w ill be sh o wn o n p ag e 7 9
Th e e n tire t u be was l a ter he a te d i n a c u rre n t o f p u re a ir a t a te m per a
t u re a bo v e t h e boili ng poi n t o f su lp hu ric a ci d f or a bo u t 5 m i nu te s i n or d er
to d ri v e o u t any po s s ible a cci d e n t a l tr a ce o f a ci d i n t h e t u be W h ile s till
wa rm it was pl a ce d i n a d e s icc a tor and l a ter w ei gh e d Th e t u b e w a s k ept
h orizo n t a l u n til t h e e nd o f t h e e x peri m e n t to av oi d any c han ce o f m ech an
i c a l l o ss
Th e d e v ice o f s pre ad i ng the sa lt i n a t h i n l ay er a ro und t h e t u be b y rot a t
i n g t h e t u be du ri ng t h e cooli ng had f o u r v er y i m port an t advan t ag e s
F ir s t t h e c han ce o f bre ak i ng t h e v er y f r ag ile qua rtz t u be du ri ng t h e s oli d
i fi ca ti o n and cooli n g was g re a tl y re du ce d b y t h e m ore e v e n d i s trib u ti o n o f
t h e s tr a i n ; s eco nd l y t h e sa lt w a s ag it a te d and s pre ad o u t i n a t h i n l ay er
wh ile s till fus e d i n a c u rre n t o f p u re a ir t hu s fa cilit a ti ng t h e e s c a pe o f any
p o ss ible tr a ce o f d i ss ol v e d su lp hu r trio x i d e ; t h ir d l y t h e cooli ng was mad e
m ore un i f or m and r a pi d s o t ha t t h e a r g e n tic su lp ha te had n o ti m e to
d ec om p o s e be f o re it h a d s oli d i fi e d ; and f o u rthl y a mu ch l a r g er su r fa ce
w a s e x po s e d to t h e l a ter a cti o n o f t h e hyd roc h loric a ci d
Th e po ss ibilit y j us t m e n tio n e d t ha t t h e colorle ss a r g e n ti c su lp ha te m i ght
co n t a i n an e x ce s s o f su lp hu r trio x i d e n ee d e d c a re fu l c o ns i d er a tio n U n
f ort una tel y a d irect te s t f or a ci d s ee m e d to be i m pr a ctic a ble o w i n g to the
s li gh t s ol u bilit y o f s il v er su lp ha te h e n ce li ght u po n t h e q u e s tio n was
s o ugh t i n s e v er a l d i s ti n ct ways
2
W eber has f o und t ha t i n or d er to p rep a re a co m po und An zO 7 a rge n
tic su lp ha te mu s t be h e a te d w it h su lph u r trio x i d e u nd er pre s su re i n a
s e a le d t u be
Th i s to g et h er w it h the fa ct t ha t a rge n tic su lph a te d e com
po s e s s o e as il y wh e n fus e d i nd ic a te s t ha t it d oe s n ot h av e a g re a t te nd e n c y
to ret a i n su lp hu ric o x i d e and t ha t t h e va por te ns io n o f t h e tri o x i d e i n t h e
d i su lp ha te i s fa r a bo v e t ha t ma i n t a i n e d i n t h e p re s e n t e x peri m e n t s
In
or d er t o o bt a i n quan tit a ti v e e v i d e n ce t h e p u re wh ite su lp ha te i n s i x o f the
fina l e x peri m e n t s a fter bei n g w ei gh e d was fus e d aga i n f or a bo u t 1 0
to 1 5 s eco nds i n or d er to d eco m po s e it s li ghtl y T hi s gav e a S li gh t b u t
u nm i s t aka bl e da rk color to t h e sa lt Th e re su lti ng lo ss e s o f w ei ght a re
t a b u l a te d o n p a ge 7 9
.
-
,
.
.
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h ds
p r s t p u bl i
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ar
en
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,
i
We l l s
ca t o n ,
B er
.
,
17,
p
,
55
2 50 3
.
s Pu b
C a r n eg i e I n t
.
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2 8, 3 1
( 1 90 5 )
h ds
Ric
ar
an d
For b es
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F U SIO N
TH E
Th e L os s
No
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o
We i gh t
e p e r i me n t
x
e
A g2 SO 4
.
79
.
s e d b y S l i g h t D e compos i ti on
Ca u
Wh i t
of
.
A RGEN T I C S ULP H AT E
OF
'
D
a rk e n e d
A g 80
2
.
,
D me m n Ce
.
°
.
5 16 l 3 8
.
T he lo ss i n w ei gh t
t hus o n t h e av er ag e o n l y
m g or
pe r
ce n t In s ee ms cert a i n t ha t a t le as t p a rt o f t h i s lo ss i n w ei g ht w a s du e to
a d e fi cie n c y o f eit h er o xyg e n or su lph u r trio x i d e i n t h e da r k e n e d su lp ha te
and n ot to t h e lo s s o f an ille g iti ma te e x ce s s o f t h e l a tter su b s t an ce T here
f ore a ltho ug h i t may b e a d eb a t a ble q u e s tio n as to w het h er it i s sa f er to
t a ke the w ei ght o f the w hite or da r k e n e d sam ple s as the tr u e w ei ght it
s ee m s prob a b le th a t the w eigh t o f t h e wh i te sam ple w a s m ore tr u s t w ort hy
E v e n a t t h e w or s t t h e un cert a i n t y c an n ot hav e bee n gre a ter t han
per ce n t T h i s re s u lt ag ree s w ith t h e e a rlier co n cl us io ns a lre ady cite d co n
cer n i ng t h e O b v io us e ff ect o f v ery S li gh t d ecom po s itio n o n t h e color o f S il
v er sa lt s I t a ppe a r s th a t i n t h e pre s e n t c as e as i n t h e ot h er s the s li g ht
s t a bilit y o f t h e s e co m po unds i s a re a l as s i s t an ce i n t h e pro du ctio n o f a
t y pic a l co m po und i ns te ad o f a hi nd r an ce to preci s e q uan tit a ti v e w ork
F o r w ei gh i n g the a r g e n tic su lp ha te and o f co u r s e t h e c h lori d e a l s o
the T r o em n e r b a l an ce w hich h ad s er v e d i n many s i m il a r re s e a rche s was
used
T h e S a rtori us pl a ti n ize d b r as s w ei gh t s w ere s t anda r d ize d b y the
u sua l H a r va r d m et h o d
A S u su a l a ll w ei g hi ngs w ere mad e b y su b s tit u tio n a ma ke w eight bei n g
pl a ce d o n the righ t h and b a l an ce p an In or d er to av oi d a s fa r as po s s i b le
any error du e to ch an gi n g me teorologic a l co nd itio ns a su b s tit u ti n g co un
t e r po i s e o f t h e sam e ma teri a l and a ppro x i ma tel y t h e sam e su r fa ce and
w ei ght wa s us e d E v er y w eighi n g w a s repe a te d and the su cce ss i v e va l u e s
s el d o m d i f f ere d m ore t han
m g N o d i f fi c u lt y wa s e x perie n ce d f ro m
h yg ro s copic ads orptio n o f wa ter b y either a rge n tic su lph a te or a rge n ti c
chl o ri d e e x cept o n a f e w days w he n the a ir was unu sua ll y hum i d In t h e s e
c as e s t h e t u be w a s he a te d to abo u t 3 3 0 and a llo w e d to re ma i n i n a d e s ic
c a tor un til the co nd itio ns w ere m ore fav or a ble T h e t u be was a l ways
a llo w e d to re ma i n a t le as t t h ree ho u r s i n a d e s icc a tor n e a r the b a l an ce
wa s
.
.
,
.
,
,
.
.
.
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,
,
1
.
2
.
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,
,
-
.
,
.
,
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,
°
.
h ds Pro A me r A a d 2 6 2 42
h ds J A m e r C h m S oc 2 2 1 4 4
Ri c
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,
GEN T I C S ULP H A T E
M O LE C UL A R WE I GH T O F
80
AR
,
E TC
.
be f ore mak i n g a w eigh i ng and du ri ng t h i s ti m e was co v ere d by a bl a c k
clot h to p rotect t h e s e ns iti v e sa lt s f ro m t h e li gh t
In or d er to correct t h e w ei gh t s to t h e va c uum s t anda r d the s peci fi c
g r av it y o f a r g e n tic su lph a te i s n ee d e d F ollo w i ng a re the p u b li s he d re su lt s
co n cern i ng t h i s da t um :
.
,
.
lph a te
f A r ge n ti c S u
D e n s i ty
s
o
S ch w e i g g e r s J 6 5 4 1 9
P l ay f a i r a n d J o u l e M e m C h e m
F i l h ol A n n C h i m e t P h y s
K a r te n ,
’
.
,
,
,
.
S ch r Od e r ,
P et te r s on
.
,
,
.
.
.
S oc , 2 , 4 3 0
.
2 1 , 4 17
.
P ogg A n 1 0 6 2 4 5
U ps a l a N ov a A cta
n
.
.
,
,
9,
,
35
A f ter a s t udy o f t h e ori g i na l p a per s t h e va l u e
was pro v i s io na ll y
ad opte d a s t h e m o s t prob a ble va l u e ; b u t as there was s o m e d o u bt a bo u t
it s a cc u r a c y t h i s w a s v eri fi e d b y e x peri me n t
Th e d e ns it y o f t h e tol u ol to be d i s pl a ce d b y the sa lt was d eterm i n e d b y
m e ans o f an Os t wa l d p y c n o m eter a t 2 9 2 to be
( t h e m e an o f 3
co n cor dan t d eter m i na tio ns )
grams o f pre v io us l y fu s e d s il v er s ul
p ha te w ere f o und to d i s pl a ce
gr am O f t h i s tol u ol and t h ere f ore
occ u pie d
m l ( t h e m e an o f t w o d eter m i na tio ns ) H e n ce t h e d e ns it y o f
a r g e n tic su lp ha te i s
as su ppo s e d Th i s i nv ol v e s an add iti v e co r r e c
tio n o f
g r am to e a c h a pp a re n t gr am o f t h e sa lt a va l u e w h i ch
i s d ecre as e d
b y an i n cre as e o f a ce n ti m eter o f a t m o s p h eric
p re s su re or d ecre as e d
b y an i n cre as e o f a d e g ree o f te m per a
t u re T h e correctio n to t h e w ei gh t was a pplie d a ccor d i ngl y
,
,
,
.
°
,
.
.
.
,
,
.
.
THE CO N VERS IO N
OF
A RGEN TI C S U LP H A TE
I NTO
CHL
ORI DE
.
T h e n e x t s tep i n t h e proce s s was the co nv er s io n o f the c a re fu ll y
w ei gh e d fus e d su lph a te i n to c h lori d e b y h e a ti n g it i n a c u rre n t o f d r y
1
h yd roc h lori ca ci d gas T hi s re a ctio n h as b ee n Ob s er v e d b y H en s ge n
Th e hyd roc h loric a ci d g e n era tor u s e d for the p re v io u s w or k was co n
s tr u cte d e n tirel y o u t o f g l as s P u re amm o n ic c h lori d e or co n ce n tr a te d
h yd roc h lori c a ci d was pl a ce d i n t h e flask ( 1 ) sh o wn i n figu
re 4 an d co n
ce n t r a t e d su lph u ric a ci d w a s d roppe d u po n it S lo w l y
T he ga s w a s d rie d b y
p ass i n g t h r o ugh t h e to w er ( 1 ) co nt a i n i n g be ads m oi s te n e d w ith co n ee n
.
.
.
,
.
u
ux h
u s
P s
H e n s g e n , R e c e i l d es T r a v a
B as , 2 , 1 24
Le
c im iq e
de
ay
’
m é ga g e m e n t
l f at e (1 a rgen t a b or b a 2 m ol H C l 4 l a t e mp er a ture o r i n a i r e , a v e c u
d e c a l e r n ot a bl e , e t s e c an ge a com l et e m en t e n c l o r r e
E n c a ff a n t, m em e
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M O LE C UL A R W E I GH T O F
82
GEN T I C S ULP H A T E
AR
E TC
,
.
u r fa ce a t i n ter va l s o f a b o u t 1 m i nu te b y g r as pi ng t h e e x it e nd w ith
pl a ti nu m fo rcep s Th e a g it a ti o n c an be per fo rm e d w it h o u t dang er o f lo s s
bec aus e o f t h e h i gh su r fa ce te n s i o n o f fus e d a r ge n tic c h l o ri d e Th i s ma te
ri a l wh e n li qu e fi e d d oe s n ot adh ere t o qua rtz and t h ere f ore i s n o t d r awn
i n to t h e e nd t u be s b y c a pill a rit y A t t h e e xpir a ti o n o f 2 0 m i nu te s t h e
c u rre n t o f a ci d gas was s toppe d b y m e an s o f t h e s topc o c k ( K ) a n d a c u r
r e n t O f p u re d ry a i r wa s p ass e d t h ro ugh t h e t u be t h ro ugh L t h e a rg e n tic
c h l o ri d e bei ng s till ma i n t a i n e d i n t h e li qu i d s t a te f o r a t le as t 5 m i nu te s
w it h o cc as i o na l ag it a tio n Th e t u be w a s rot a te d wh ile su b s e qu e n tl y cool
i ng i n a s i m il a r mann er to t ha t e m pl o y e d w it h t h e su lp ha te
Th e co nd e n s e d su lp hu ric a ci d e v o l v e d b y the re a cti o n and th e co nd e ns er
1
t u be w ere te s te d f or s il v er b y m e ans o f t h e n ep h el o m eter Th e a ci d was
tr ans f erre d to a s m a ll flask and t h e t u be w a s ri ns e d w it h amm o n i a wh ic h
was add e d to t h e a ci d Th e e x ce ss o f amm o n i a wa s t h e n n e u tr a lize d w it h
n itric a ci d a n d hyd ro c h l o ric a ci d w a s add e d t o precipit a te any tr a ce o f
s il v er pre s e n t a s an op a le s ce n t cl o u d o f a r g e n tic c h l o ri d e Th i s op a le s ce n ce
w a s co m p a re d i n t h e n ep h el o m eter w it h a s t anda r d wh i c h had bee n m ad e
i n a m ann er v er y S i m il a r t o th e unkn o wn s ol u ti o n A m e asu re d v o l um e o f
a s t anda r d S il v er s ol u tio n was t ak e n ; to it w ere add e d a ppro x i ma tel y t h e
sam e am o un t s o f su lp hu ric a ci d amm o n i a and n itric and hyd roc h loric
a ci ds as w ere pre s e n t i n t h e unkn o wn s ol u tio n ; and it w a s mad e u p t o t h e
sam e v ol um e ( a bo u t 3 0
T h e g re a te s t a m oun t O f a r g e n tic c h lori d e t hu s fo und i n any e x peri m e n t
was
g r am and t h e av er ag e am o un t
g ram Th e tr a ce
fo und i n t h i s way wa s o f c o u r s e add e d to t h e w e i gh t o f t h e S il v er c h l o ri d e
In t h ree o f t h e e x peri m e n t s ( NO S 4 5 and 7 ) t h i s d eter m i na ti o n w a s n ot
mad e b u t t h e av er age a m o un t i s add e d i n t h e s e c as e s Th e prob a ble re a
s o n f o r t h e e s c a pe o f t h i s tr a ce o f S il v er w ill be d i s c u ss e d l a ter
Th e qu e s ti o n as to wh et h er o r n ot t h i s re a cti o n i s c o m plete i s o f c o u r s e
o f funda me n t a l i mport an ce Th ere a re f o u r piece s o f e v i d e n ce be a ri ng
o n th i s po i nt
In t h e fi r s t pl a ce t he a r g e n tic c h lori d e w a s fu s e d f o r t w e n t y m i nu te s i n
a c u rre n t o f a l m o s t p u re hyd roc h l o ric a ci d S i n ce t h e te m per a t u re w a s
fa r a b o v e th e b o ili n g p o i n t o f s u lp hu ri c a ci d t h i s pro du ct o f t h e re a ctio n
w a s d ri v e n o ff as f a s t a s fo r m e d
Th ere fo re a cc o r d i ng to t h e l aw o f
c o n ce n tr a ti o n e f f ect it i s to be e x pect e d t h a t t h rou gh t h e a ge n c y o f t h e
c o n ti nua ll y re n e w e d hyd r o c h l o ric a ci d a ll t h e a r g e n tic su lp ha te w o u l d be
d ec o m p o s e d and a ll t h e su lp hu ric a ci d w o u l d be d ri v e n o ff
Th i s w o u l d
be has te n e d b y th e fa ct t ha t f re sh su r fa ce s w ere c o n ti nua ll y e x p o s e d
t h ro ugh agit a ti o n
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TH E C
A ga i n
O N V E RSIO N
AR GEN T I C S UL P H A T E I N T O
OF
C
H L ORID E
83
.
t h i s c as e t h e l aw o f co n ce n tr a ti o n e ff ect i s a ss i s te d b y the rel a
ti v e a f fin it y i n d i c a t e d a ppr o x i ma tel y b y t he l a r g e am o un t o f h e a t e v ol v e d
b y t h e re a cti o n I t c an be c a lc u l a te d f rom Th o m s e n s da t a t ha t t h e r e a c
tio n g i v e s out
g r am s c a l o rie s o r 1 7 0 k il o j o u le s R a rel y i f e v er i s
t h e d i ff ere n ce bet w ee n t o t a l —e n er gy and f ree e n er gy c hang e s i n a re a cti o n
o f t h i s k i nd a s g re a t as t h i s he n ce it i s sa f e to i n f e r t ha t t h ere i s a co n
s i d e r a b l e prep o nd er an ce O f d ri v i ng te nd e n c y i n t h e d e s i re d d irectio n a ri s
i ng f ro m t h e mu t ua l a ffin itie s co n cer n e d
Th i r d l y co ns t an c y o f t h e w ei gh t o n co n ti nu e d tre a t m e n t i n d ic a t e d t h e
c om pletio n O f t h e re a cti o n I n s e v e n o f t h e e x peri m e n t s t h e a r ge n tic
c h l o ri d e was fu s e d a s ec o nd ti m e i n hyd ro ch l o ric a ci d f o r 1 5 m i nu te s w it h
f o llo w e d b y 5 m i nu te s i n a i r Th e fo llo w i ng t a ble
o cc as i o na l ag it a ti on
g i v e s t h e c ha n g e s i n wei gh t f o u nd i n thi s way
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bei n g o n l y
per ce n t O f t h e w eig h t o f t h e c h lori d e
Th i s e x peri m e n t h o w e v er d o e s n ot a b s ol u tel y precl u d e t h e po ss i b ilit y
t ha t a sma ll b u t co ns t an t a m o un t o f su lph a te m ay re ma i n In or d er to te s t
t h i s q u e s tio n
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t a m i n a t e d w ith su lp ha te wa s fu s e d i n t h e t u be and t h e n
g r am O f
p u re a rg e n tic su lp ha te was add e d and t h oro ug hl y m i x e d w ith t h e c h lori d e
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MO L E C UL A R
84
WE I GH T O F A RGEN TI C S U L P H A T E
,
E TC
.
chlori d e t h e mass b ei ng tr ans l u ce n t or a l m o s t op aqu e i ns te ad o f tran s pa r
e n t I t was t h e n fus e d i n a c u rre n t o f hyd roc h loric a ci d f or t w e n t y m i nu te s
a fter t h e su lp hu ric a ci d c o u l d n o lo nger be s ee n e s c a pi ng f ro m t h e t u be a s
be fore On t h e assu m pti o n t ha t t h e su lp ha te was co nv erte d c o m pletel y
i n to c h l o ri d e t h e l o s s i n w ei gh t w o u l d hav e bee n
g ram wh ile t h e
a ct ua l l o s s i n w ei gh t was
g r am Th e re a ctio n was e v i d e n tl y co m
pl e te and a f o u rt h a r gum e n t was add e d to t h e o th er re as o ns f or b e l i e v
i n g t ha t t h e pr o ce ss sh o u l d y iel d sa ti s fa ctory re su lt s
I t w ill be rec a lle d t ha t t h e na rro w e nd t u be s w ere k ept v er y hot b y sma ll
s t a tio na r y b u r n er s i n or d er to pre v e n t t h e co nd e nsa tio n o f su lp hu ric a ci d
A t t h e clo s e o f s e v er a l o f t h e e x peri m e n t s a v er y s ligh t su bli ma te was
O b se r v e d o n t h e p o rtio n o f t h e na rro w t u be s wh ic h was k ept s o m e wha t
c o oler b y t h e protecti o n o f t h e su pporti ng h oo ks Th i s su bli ma te a lt h o ugh
n e v er l a r g e i n a m o un t a ppe a re d l a r g e s t i n e x peri m e n t s 6 and 1 0
Th ere
was a s m a ller a m o un t i n e x peri m e n t s 7 1 1 and 1 4 b u t n o n e w ort hy o f
c o ns i d er a ti o n i n e x peri m e n t s 4 5 1 2 1 3 and 1 5 In e x peri m e n t s 1 0 and
1 4 a S li gh t a m o un t o f t h e su bli ma te was v i s ible i n t h e co nd e ns er a l s o n e a r
t h e e nd o f t h e t u b e
A lt h o ugh t h e m o s t r a tio na l e x pl ana ti o n o f t h i s tr a ce o f su bli ma te wh ic h
was usua l l y too s li gh t to be w ei gha ble was prob a bl y to be f o und i n t h e
assu m pti o n t ha t it was a r g e n tic c h l o ri d e and there f ore e n tirel y w it h o u t S i n
i s ter m e an i ng e x cept as sugg e s ti ng t h e ri sk o f t h e lo ss o f ot h er tr a ce s
t h e m a tter was s t ud ie d fu rt h er C a re fu l te s t s f o r a r s e n ic and copper w ere
mad e w it h n e ga ti v e re s u lt s and t h e hyd ro c h loric a ci d was d e m o ns tra te d
to c o n t a i n n o tr a ce o f any t h i ng wh ic h co u l d be d epo s ite d i n a re d h ot
q ua rtz t u be On t h e ot h er hand t h e su bli ma te was s ol u ble i n a m m o n i a
and be hav e d i n e v er y way li k e a rg e n tic c h l o ri d e S O t ha t it s na t u re wa s
co ns i d ere d as n e a rl y pro v e d as w a s po ss ible w it h su c h a m i nu te am o un t o f
m a teri a l
H av i ng s ettle d t h e na t u re o f t h e su bli ma te it s s o u rce and s i gn i
fi ca n ce m u s t be tr a ce d
E v i d e n tl y it co u l d n ot hav e c o m e f ro m t h e ma i n
b o dy o f t h e s il v er su lp ha te bec au s e it a ppe a re d a t t h e v er y be g i nn i ng o f t h e
e x peri m e n t as s o o n as t h e c u rre n t o f hyd roc h loric a ci d was s t a rte d and
t h e e nd t u be s h e a te d be f ore t h e h e a t was a pplie d to t h e m a i n b o dy o f t he
a r g e n tic s u lp ha te Moreo v er t h e mass O f t h e a rg e n tic c h lori d e was n e v er
h e a te d to a te m per a t u re h i gh e n o ugh to v ol a tilize w ei gha ble am o un t s o f
t h i s su b s t an ce a s was Sh o wn b y t he co ns t an c y o f w ei gh t o n co n ti nu e d
he a ti ng i n a c u rre n t o f gas
In v ie w O f t h e s e co n s i d era ti o ns it s ee m e d pr o b a ble t ha t a f e w i nv i s ible
crys t a l s o f a r ge ntic su lp ha te had bee n le f t i n t h e e nd t u be s b y t h e f e a t h er
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2
S e e th e pr e c e d i n g d e s c r i p t i o n ; a l s o R i ch a rds a n d We ll s
P r oc A m e r A ca d 4 1 83
1
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60 ;
B xt r
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A RGEN T I C S U L P H A T E I N TO
TH E C O N V E RSIO N O F
O ID E
CH L R
85
.
us e d i n cle an i ng it or c a rrie d i n to th e e nd t u be b y t h e c u rre n t o f su lp hu r
trio x i d e be f ore fu s io n A s s oo n a s t h e hyd roc h lori c a ci d was ad m itte d and
t h e e nd t u be s h e a te d t h e s e sma ll i nv i s ible cr ys t a l s o f s il v er su lp ha te mu s t
hav e bee n a t o n ce co nv erte d i n to c h l o ri d e and su bli m e d to t h e c o oler po r
tio n o f t h e t u be
f or t h e e nd t u be s w ere u sua ll y r a i s e d to a re d h e a t Th i s
e x pl ana tio n i s co ns i s te n t w it h t h e f re qu e n t a b s e n ce o f any s i gn i fi c an t s ub
li ma te e s peci a ll y i n t h e c as e o f e x peri m e n t 1 5 In t h i s e x peri m e n t t h e
t u be ha d bee n du s te d and tre a te d w ith p a rtic u l a r c a re i n or d er to te s t t h e
poi n t
Bec au s e t h e su bli ma te w a s w ei gh e d i n t h e t u be whi c h had pre v io u s l y
c o n t a i n e d t h e su lp ha te i ts pre s e n ce c o u l d n o t a f f ect t h e a cc u r a c y o f t h e
re su lt s e v e n i f it h ad bee n w ei gha ble N e v ert h ele ss t h e sugg e s ti o n t ha t
an o t h er porti o n m i gh t hav e bee n c a rrie d o u t o f t h e t u be wa s w o rt h co n
s i deri ng
D o u bt s o n t h i s poi n t w ere s e t a t re s t b y t h e ana l ys i s o f t h e co n
te n t s o f t h e co nd e ns er t u be wh ic h recei v e d t h e v o l a tile pro du ct s o f t h e
re a ctio n Th e av er ag e am o un t o f S il v er fo und i n t h i s t u be was le s s t han
per ce n t o f t ha t t ak e n i n e a c h e x peri m e n t and t h e sma ll a ppropri a te
c o rre ctio n w a s e as il y a pplie d
A lt h o ugh it w a s n o t p ro b a ble t ha t a rg e n ti c c h lori d e wh ic h had bee n
fu s e d i n a ir f or fiv e m i nu te s s till ret a i n e d any d i ss ol v e d hyd ro c h loric a ci d
t h i s p o i n t a l s o w a s te s te d In e x peri m e n t 1 3 t h e S il v er c h l o ri d e af ter t h e
fi r s t h e a ti ng i n h y d roc h loric a ci d and fu s io n i n a ir f o r fiv e m i nu te s as
u sua l w ei gh e d
g r am s A f ter t h e s eco nd fu s i o n i n hyd ro c h loric
a ci d a nd fina ll y i n a ir t h e w ei gh t was
g r ams A f ter an o t h er
fu s i o n f o r t w e n t y m i nu te s i n a c u rre n t o f p u re a i r t h e w ei gh t was
g r am s T he s e s li gh t c hang e s i n w ei gh t c an o n l y be as cribe d to error s i n
t h e w ei gh i ng ; t h e o u tc o m e sh o w s t ha t th e a r g e n tic c h l o ri d e af ter t h e u sua l
tre a t m e n t d i d n ot r e t a i n any d i ss ol v e d hyd roc h l o ric a ci d R ic ha r d and
Well s hav e a lre ady Sh o wn t ha t it d oe s n ot d i ss ol v e w ei gha ble am o un t s
o f a ir
In s till an o t h er c as e t h e o u t s i d e o f t h e t u be was w a she d w it h wa ter to
mak e su re t ha t n o t h i ng had d ep o s ite d on it du ri ng t h e lo ng e x p o su re to
m g wh ic h aga i n i s
Th e lo s s i n w ei gh t w a s o n l y
t he flam e and a ci d
n ot g re a ter t han t h e po s s ible error i n w ei gh i ng
,
.
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,
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.
.
,
.
,
.
,
.
,
.
,
,
,
.
.
1
.
.
,
.
i
h r ds
1R c
a
an d
We ll s
,
l oc
.
ci t
.
,
p
.
60
.
M O LE C UL A R WE I GH T O F AR GEN T I C S UL P H A T E
86
ETC
,
FINAL
TH E
RES
U LTS
.
.
H av i n g
sh o wn t h e f e as ibilit y o f t h e pl a n o f O per a tio ns and ga i n e d pra c
t i ce b y t h ree preli m i n a r y e x peri m e n t s a fina l s erie s was und ert ak e n wh o s e
o u tco m e i s d et a ile d bel o w
S am ple A O f a r g e ntic su lp ha te was u s e d i n e xp e ri m e n t s 4 a n d 5 and
s a m ple B i n t h e re ma i nd er In e x peri m e n t s 5 and 6 t h e hyd r o ch l o ric a c i d
was ge n er a te d f ro m a m m o n ic c h l o ri d e and i n t h e o t h er e x peri m e n t s f ro m
c o n ce n tr a te d hyd ro c h loric a ci d Th e correcte d w e i gh t o f a r g e n tic c h l o ri d e
was obt a i n e d b y add i ng t h e tr a ce f o und i n t h e c o nd e ns er to t h e av erag e
w ei gh t a f ter fus i o n i n hyd ro c h l o ric a ci d In e x peri m e n t s 4 5 and 7 the
correcti o n f or t h e a r g e n tic c h l o ri d e i n t h e co nd e ns er was n ot d eterm i n e d
d i rectl y b u t t h e m e an o f t h e ot h er d eter m i n a tio ns
g ram ) was
add e d
In e x peri m e n t s 8 and 9 t h e na rro w e x it t u be bec am e co m pletel y bl o c k e d
o f t h e a r g e n tic c h l o ri d e
b y t h e creepi nng
Th i s mad e it n ece ssa ry to fu s e
g O
t h e s oli d wh ile t 1h ere was s til
till pre s e n t co ns i d er a ble a r g e n tic su lp ha te ; and
t h ere fo re t h e su lp hu ric a ci d boile d and ma teri a l w a s l o s t b y bei ng p r o
j e cte d o u t o f t h e t u be Th e fi r s t o f t h e s e was re j ecte d and t h e s eco nd n ot
fin i sh e d A ll t h e ot h er d eter m i na tio ns a re rec o r d e d i n fu ll i n t h e t a ble
Th e w ei gh i ngs hav e o f co u r s e bee n c o rrecte d to t h e va c uum s t anda r d
,
,
.
‘
.
,
.
.
,
,
,
.
.
.
,
.
.
.
Th e Q u
a n ti ta ti v e C on v e r s i o n
No
x
W
of
e p eri me n t
.
e g ht
e ss
i
l
.
o
of o l o r
c
Ag so4
2
i n a u um
v
f A r ge n ti c S ul ph a te
c
W
i
h
t of
Io t a l A gC l
v
.
eg
a u um
c
'
m
.
P
o
to C h l or i d e
.
I
f
ggi i d ti g
p r t s of
s
n
a
A g2 80
4
.
Thu s
p a rt s o f colorle ss a r g e n tic su lp ha te w ere fo und to y iel d
“
p a rt s o f a r g e n tic c h l o ri d e w it h a van i sh i ngl y sma ll prob a ble
erro r
I f t h e w ei gh t o f t h e da rk e n e d sa m ple s a re u s e d i n t h e c a lc u l a ti o n
t h e re su lt becom e s
a va l u e w h ic h cert a i n l y repre s e n t s t h e max i
mum To hav e re du ce d t h e c h ie f un cert a i n t y to w it h i n su c h na rro w li m it s
was t o hav e s ol v e d t h e pro ble m as fa r as it n ee d be s o l v e d a t p re s e n t
Th e i n terpret a ti o n o f t h e re s u lt a l o n e re ma i ns
,
”
.
.
.
.
T H E F I N A L RE S UL T S
87
.
c o m p a ri ng t h i s re su lt w it h t ha t o f S t as o n a r g e n tic su lp ha te it may
be n o te d t h a t S t a s f o u nd i n s il v er su lp ha te
per ce n t o f S il v er B e
I II
,
.
100
per ce n t it i s cle a r t ha t o u r re su lt s i nd ic a te
"
per ce n t o f s il v er i n s il v er su lp ha te or
le s s t han S t as s o n e i s f orce d
t o t h e co n cl u s i o n t ha t S t as s a r g e n tic su lp ha te w a s n ot co m pletel y re du ce d
b y hy d ro g e n and t ha t h i s s il v er Obt a i n e d i n t h i s way wa s no p u
r er t han
t h e S il v er u s e d i n h i s other w o r k Th e o n l y te s t o f c o m plete re du cti o n
u s e d a t the ti m e was t h e s o l u ti o n o f t h e re s i dua l m e ta l i n n itric a ci d ; b u t
t h i s te s t co u l d n ot re v e a l und e c o m p o s e d s u lp ha te and m i gh t n ot re v e a l
tr a ce s o f su lphi d e
,
’
,
,
’
,
,
.
,
I
.
TH E
A T O M I C WEI G H T
O F S U LP H UR
.
Th e i n terpret a tio n O f t h e n e w re su lt s i s v er y S i m il a r to t ha t a l re ady d i s
c u ss e d i n t h e p rece d i ng p a per o n n itro g e n and s il v er In t h i s c as e as i n
t ha t t h ere a re tw o u n cert a i n r a tio s ; and on e o f t h e s e r a ti o s nam el y t ha t
n ce r
o f S il v er to o xyg e n o cc u r s i n e a c h
In t h e pre s e n t c as e t h e ot h er u
t a i n r a tio i s t ha t o f su lp hu r to o xy ge n Wh ile i n t h e f or m er c as e t h e oth er
u n cert a i n r a ti o w a s t ha t O f n itro g e n to o xyge n
In or d er to obt a i n a co m plete s o l u tio n o f t h e num eric a l rel a tio n s i n either
o f t h e s e c as e s it i s t h ere f ore ob v io u s l y n ece ssa r y to obt a i n an ot h er s erie s
o f re su lt s bri ng i n g i n su c h a r a ti o as t ha t o f s il v er to su lp hu r or o xyg e n
S u c h an add itio na l r a tio i s n ot kn o wn
to su lp hu r or c h lori n e to o xyg e n
a t pre s e n t w ith m o d er n a cc u r a c y
Bec au s e o f t h e fa ct t ha t S il ver and
o xyg e n a re co n cer n e d i n e a c h o f the c as e s a s i n gl e n e w re su lt properl y
c h o s e n w ill s ol v e bot h p roble ms a t o n ce ; b u t o f co u r s e many n e w re su lt s
w ith d i ff ere n t co m po unds co nfi r m i ng o n e an ot h er a re g re a tl y to be
A s has bee n sa i d i n the f ore go i ng p a per s o m e o f t he s e a re
d e s i re d
a lre ady i n t h e proce s s o f d eter m i na tio n a t H a r va r d C olle g e and it i s
i n te nd e d to p u r su e t h e ma tter fu rther a t t h e U n i v er s it y o f Berli n as w ell
F o r the pre s e n t it i s n ece ssa r y to s t a te t h e i n terpret a tio n o f the re su lt s
i n a c o nd iti o na l mann er as sum i ng va ri o u s p o ss ible r a tio s bet w ee n o xyg e n
and s il v e r and s t a ti n g t h e corre s p o nd i ng va l u e s f or su lp hu r In t h e f u
t u re wh e n t h e a s sum e d rel a ti o nsh ip i s repl a ce d b y kn o w le dg e o f t h e fa ct s
i n telli g e n t c h o ice c an be mad e bet w ee n t h e a lter na ti v e s
I f o xyg e n i s t ak e n a s
t h e fo ll o w i ng t a ble g i v e s t h e a to m ic
i c w ei gh t s o f s il v er
w ei gh t s o f s u lp hu r c o rre s po nd i ng to t h e s e v er a l a tom.
,
,
,
,
.
,
,
,
.
,
,
,
.
,
.
,
,
,
,
,
,
.
,
.
,
.
,
,
,
.
.
A to mi c
I f Ag
I f Ag
I f Ag
We i gh t of
CI
an d C 1:
a n d Cl :
an d
r
S ul ph u
.
S
8
S
13
M O LE C UL AR WE I G H T
88
OF
AR GEN T I C S ULP H A T E
,
E TC
.
Th e lo w e s t v a l u e i n t h i s c a s e as w ell as i n t h e c as e o f n itro g e n i s t h e
o n e su pp o rte d b y t h e rece n t w o r k o n t h e d e n s itie s o f g a s e s
In co n c l u s i o n it i s a ple a s u re to a c kn o w l e dg e t h e g e n er o u s ass i s t an ce
w it h o u t wh ic h t h e pre s e n t
o f t h e C a r n e g ie Ins tit u ti o n o f W ash i ngt o n
w o r k c o u l d n ot hav e bee n per f orm e d
,
,
.
,
,
.
S U MM A R"
.
Th e m o s t i m p o rt an t re su lt s o f t h e re s e a rc h may be brie fly summ e d u p as
f ollo ws :
( 1 ) A m et h o d f o r t h e prep a r a ti o n o f p u re a r ge n tic su lp ha te was d e v i s e d
( 2 ) Th e s peci fi c g r av it y o f a r ge n tic su lp ha te ( pre v io u s l y fus e d ) was
fo und to be
3 ) Ind ic a ti o n w a s o bt a i n e d t ha t S t a s was una ble wh oll y t o re du ce s i l
v e r su lp ha te i n hy d r o g e n
4 ) A r g e n tic s u lp ha te w a s f o und t o be o ccl ud e d b y s il v er c h l o ri d e f ro m
s o l u ti o ns c o n t a i n i ng an e x ce ss o f su lp hu ric a ci d
( 5 ) I t was pro v e d t ha t a r g e n tic s u lp ha t e c an be c o m pletel y c o nv erte d
i n to s il v er c h l o ri d e b y h e a ti ng i n a c u rre n t o f hyd roc h l o ri c a ci d gas
6)
p a rt s o f a r g e n tic su lp ha te w ere t hu s fo und to y iel d
p a rt s o f a r g e n tic c h lori d e
( 7 ) Th e a t o m ic w ei gh t o f s u lp hu r as c a lc u l a te d f ro m t h i s r a ti o i f
o xyg e n i s t ak e n as
w it h s e v er a l assum e d va l u e s f or s il v er i s :
.
.
.
.
.
,
Ag :
Ag
s
Ag 2 :
S
A tte n ti o n i s c a lle d a l s o
on
p ag e s
2 4 , 44 ,
and
65
.
to
2
t h e sum m a rie s
of
t h e t h ree pre v i o u s p a per s