C H A P T E R - IV
DETgJiMINATION OF ZINC BY PRECIPITATION OF ZINC AMMONIUM
PHOSPHATE FROM HOMOGENEOUS SOLUTION
DET,RMINATION OF ZINC BY PRECIPITATION OF ZINC AMMONIUM
PHOSPHATE FROM HOMOGENEOUS SOLUTION
SUMMARY
An invesUgation was carried out for the preoipi tation
of Zino ammonium phosphate from homogeneous solution using
disodium hydrogen phosphate as precipitant and a quantitative
method has been developed.
The method is based on the
solubility of zino ammonium phosphate in ammonioal solution
due to the forma·tion of zino ammonia complex, Zn(NH.3)++ •
4
When the ammonioal solution is heated, ammonia is volatalised
and free zino ions are gradually liberated causing a slow
precipitation.
Optimum pH for the precipitation is found
to be 7. 0 - 7.8.
Hydroxides of iron, chromium and aluminium,.
e.nd phosphates of barium, strontium, oaloium and manganese
will be preoeipitated, if present, from the ammon1a1 solution
whereas Zinc will remain in solution.
This property is used
for the separation of these metals from zino.
Anions suoh as
sulphate, acetate and chloride in the form of ammonium salta
do not interfere upto 50 mmoles, but show interference if
present as the alkali salts in concentrations mo.re than
10 mmoles.
Zino has been determined in presence of nickel
after oomplexing with tartrate.
Copreoipitetion of cadmium
with zino in this determination hae been studied using Cd-115
traoer.The
in Brass.
~ethod
has been applied for the determination of zinc
•
95
DET~RMINATION
OF ZINC BY PRECIPITATION OP ZINC AMMONIUM
PHOSPHATE PROM HOMOGENEOUS SOLUTION
All the ti trimetrio methods for the determination
of zinc, with the exception of oomplexometric procedures,
are based on precipitation reactions.
It ia observed that
these methode suffer trom most of the errors of the
corresponding gravimetric procedures, and in aJdition,
other errors introduced by nature of titrimetrio procedures
themselves1 • The electrolytic determination of zinc is not
so accurate and is used chiefly for the separation of zinc
from certain elements and it can not be applied for quant:Hative
determination until preliminary separatiore have been made.
A number of methods are available for the
gravimetric detdrmination of zinc bu.t none of the methods
are useful for the separE.tion and determinatlo.n of the metal.
in presence of aeveral common ions.
Considerable research
has been performed o.a the g:cavimetric analysi3 of zinc.
Vance anJ. Borup 2 conducted a number of experiments with
radioactive zinc using various known gravimetric methode
and oonoluded that the determimltion as sulphide, phosphate
and o:xelate have comparable
ac~racy.
Precipitation of sulphide by hydrogen sulphide
and of phosphate using diammonium hyirogen phosphate are
the most important methods tor the gravimetric estimat1ol\
ot zinc.
Zinc ~.ie also determi.aed as zinc meroury thiocyanate 3 ,
96
zinc oxinate 4 , zino anthranilite5 and zino quinoldinate 6 •
The seldom used forme of determination are ae baeio zino
carbonate 7 1 dipyridil zino thiocyanate8 , zinc oxalate9 ,
zinC 5- bromo an thranile. te
10
1
ZinC BalicylaldO Xina te
ll
and
In the determination of zinc, in the form of zinc
sulphide, the solubility and morphological properties of
the precipitate are greatly affected by hydrogen ion
conce,ltration of the solution.
One of the most widely
used methods for the precipitation of zinc sulphide is
13
that of Fales ani ·ware , in which formt.te ·buffer is
used to maintain the pH between 2 and 3.
In more ao:kdio
solution precipitation is incomplete, whereas in more
alkaline solution, slimy precipitates SI'e produced.
In
this method of determination, presence of an electrolyte,
such as ammonium sulphate or thiocyanate, is desirable to
prevent the
fo~ation
of colloidal precipitates.
Chloride
and sulphate ions contaminate the precipitate from 0.2 to
2.0 percent, if zino is precipitated in their presence.
Zinc sulphide, however, is not sui table as a weighing form
and it must be converted to zinc sulphate (ignition to
300 - 600°0) or zinc oxide (igni'tion above 940°0).
Thermogravimetric analysis shows that no region of stability
exists for either zino sulphide or zino sulphate14. Partial
separatio4 of zinc :!rom oetions o:t groups IV and V and
m&ng&Aese, oobal t and nickel oan be achieved by this method.
97
Zinc can be preoipi tated aa the white oomplex
3,15
salt, zinc mercury thiocyanate, In Rg (SCN) ,
in neutral
4
solution containi•lg not
mOL'II
than 1 ml of concentrated nitric
acid end not mor·e than 0.15 gma of zinc, by the addition o!
the precipi taut (mixture of potassium thiocyanate end
mercuric chloride).
Hydrochloric aoid interferes.
The
ions - oadmium, nickel, cobalt, manganese, mercury, chromium
and to some extent bismuth also interfere.
Preliminary
seeding of the solution is essential to get a precipitate
of theoretical composition ani a slight excess of reagent
is to be added for complete precipitation.
Zinc can be determiue:l by using anthranilic ac!d
5
at pH 4. 72 but it requ.!res different empericel gravimetric
factors depending on whethei' the precipitation is carried
out from hot or cold solution.
earth metals all
Exoept allcali and alkaline
o~;he?
QatioJJ.s interfere. The zinc can also
be determined as q_uinoldinate 6 in the pH range 2. 3 to 6. 5
but eubj eot to a numbe.r of inte.1.·ferences, particularly from
copper, sil•er, mercurous, merauric, tungsten and molybdenu~.
4
Zinc determinatio"l as oxinate achieves separation from neuly
all common interferences by :proper control of pH end using
masking agents except large amounts of nickel, oobalt and
cadmium.
Zinc has been precipitated as oxalate from homogeneous
16
solution by the hydrolysis of diethyl oxalate , but the authors
concluded that the method is of limited use because of
•
98
interferences of several ions.
Many workers
17-19
studied
the precipitation of zino sulphide from homogeneous solution
by using thioaoetamide as a aouroe for sulphide. The usa
21
of thiooarbonic acid 20 and th1ouraa
have also been reported.
Zino 8-hydroxyquinolinate has been precipitated by hydrolysis
of 8-aoetoxyquinoline 22 and by volatalisation of ammonia
method 23 •
Zinc 8-hydroxyquinaldate has alRo been precipitated
by the hydrolysis of 8-e.oetoxyquinaldine 24.
'.!:he present work describes the determiaation of
zinc ns zinc ammonium phosphate by precipitation from homogeneous
solution.
The conventional zinc ammonium phosphate method was
developed by Dakin 25. In this method the pH of the solution
is quite critical because it affects the composition as well
as solubility of the precipitate.
Even
~all
Nitrate ions interfere.
amounts of O.OlM ammonium nitrate cause low results.
Accordiag to Dakin, BOdium
OI' potaet:~iUl!l
phosphates are not
satisfactory precipitentsae they yield precipitates that are
0
onteminated by sodiWD or potassiu'll.
The one redeeming
feature of the method is the ease with which the precipitate
can be dried.
In the present method disodium hyd.rogen phosphate
is used as the precipitant.
The solubility of zinc ammonium
phosphate at higher pH due to formation of zino ammonia
++
complex Zn(NH3 ) 4 in presence of free ammonia and the slow
liberation of the zinc ions into solution by volatalisin&
ammonia causing preoipi tation of zinc ammonium phosphate,
forms the basis of the method.
99
'
'
EXPERIMENT.Al;t
REAGENTS ;-
Zinc Solution aA stock solutioa was prepareQ. by weighing about
4. 5 gms of
1
./malaR' 2inc oxide, d.isso:i.ving 1 t in ni trio
acid and diluted with distilled water to one litre.
The
zinc content was checked by titration with standard EDTA
solution, using eriochrome black - T indicator
26
•
Reagent Solution •1M solution. of disodium hyv.l'Ogan phoapb.ate
(B. D. H. 'AnalaR' ) was prepared.
All other chemicals u.sed 1o1ere of A. R. grade.
EC)UIPMENT •-
Bausch & Lomb spectroniol-20 colorimeter
WI·-•
used for colour measurements.
G. M. Counter (Medical Spectrometer, IlARC) was
used for
mea~ing
radioactivity.
pH measurements were made on Becknoan pH 11eter, H •
2
Thermogravimetric curve was recorded usin& Cahn aa
electro be.l.anoe.
Carl Zeiea Zena Allphivsl with af. •etio auto 1uuo
exposure oontrol wee used for \akin& pboto•ioroarapbe.
1Ufl
MIN 8 microsoope with low power ob~ective 9x &!ld
micrometric eye piece 5x were used for measuring sizes of
the crystal.s.
PROCEDURE a-
lO ml of ooncentrated ammonia (Sp.gr. 0.910)
and 20 ml of 1M ammonium acetate were added to a sample
solution oontaining about 1.12 mmoles of zinc in a beaker.
The volume was adjusted to about 200 ml.
To this solution,
2.5 mmoles of diaodium hydrogen phosphate were added.
About
1 ml of O.l% phenol red indicator was then added.
The beaker was heated on a steam bath for about
4 -5 hours, maintainin6 the volume by occasional additions
of distilled water.
The completeness of the precipitation
was indicated 'by the change of red oolour of the supernate
to yellow.
The pH of the supernate was found to be between
7. 2 to 7.8.
The precipitate was tranRfered to G sintered
4
e:;lass crucible and washed twice 01i th small amounts of
distilled water.
The precipitate
wa~
0
dried at 130 C in
an oven for about 30 minutes and weighed as zinc ammonium
(Conversion factor Zn/Zn NH Po4 • 0. 36645)
4
1 (J 1
DB'.rEB.MINA'UOII OP' UIIPBECIPUATED ZIIfC IN THE Jl'ILDATE
I-
a) rraoer Technique aZino-69 tracer waa prepared by irradiating
1
A.nalaR 1 Zillo metal at
1
Apsara1 , BARO, Trombay.
A stock solutioll was then prepe.:ced by dissolving
the sui table sample of irradiated zinc metal &lld the
unirradiated Zilla metal in concentrated llitrio aoid and
diluting to one litre with distilled water.
20 ml aliquot of this solution was takt'!n and
zinc was precipitated using recommended procedure.
filtrate was oolleoted and diluted to 100 ml.
The
A standard
solution was prepared by diluting 20 ml of the stock
solution to 100 ml.
Activities were measured ill both the
oases using G. M. Oounter.
Prom the rssul ts, the amount of
zinc unpreoipitated was calculated.
b) Colorimetric Method •As a check on the zinc content in the filtrate,
colorimetry was also pe·rformed by followi~ the zinc
27
dith1zonate method • Absorbance of the pink zinc
di thizonate was measured at 535 nm.
1U2
COPRECIPITATION OP QADMIUM IN THE
DETSRMI~ATION
0' ZINC AS
ZINC AMMONIUM PHOSPHATE aAliquota ( 20 ml) of Zinc solution were taken and
different amounts of cadmium tracer Cd - 115 were added.
Zinc was then precipitated ueing proposed method.
activity due
~
The
Cd - 115 in the precipitate was measured.
Simultaneously a blG.tlk oontain.i.a;!; pu1·e Od - 115 Tracer was
also precipitated and the
a~tivities
were oompared.
AP2LICATION OF THE METHOD
Determination of Zino in Brass, B.C.S.No. 5f aThe sample containing 70 to 80 mg o:f' Zino was
aoouratel:r weighed and transtered to a 400 ml beaker.
The alloy was dissolved in concentrated ni trio acid and
evaporated nearly- to dry-ness.
It was cooled and 50 ml of
water and 2.5 ml of concentrated hydrochloric acid were
added, and saturated with hydrogen sulphide gas.
The
solution was furthet• diluted to 100 ml and again saturated
with hydrogen sulphide gas.
The precipitated sulphideeof
copper, lead eto. were separated by- filtration.
The filtrate
containing zino was neutralised with ammonia a:f'ter expelling
the hydrogen sulphide gas.
the re oommended pro oedure.
The zino was then determined by
1U:l
RESULTS A.l'lD DISCUSSION
Tablt~
20 summa:daea the resul 's obtaiuttd for the
determination uf
variou.~
!1lllounta of zino by reoommended
prooedure.
TABLE 20
Precipitation of varying amounts of zino as zino ammonium
phosphate •-
Zino taken
(mg)
Zinc !ouud
(mg)
Diffel'EI!lue
(mg)
Error
(~)
9.160
9.165
+0.005
0.0546
9.160
9.164
+0.004
0.0437
18.320
lB. 320
o.ooo
o.oooo
18.320
18.332
+0. 012
0.0655
36.640
36.645
+o. 005
0.0137
36.640
36.626
-0.014
0.0382
+O, 006
0.0002
73.280
73.286
73.280
73.280
o.ooo
o.oooo
73.280
73.293
+0.013
0.01'77
73.280
73.302
+0.022
0.0300
73.280
73.288
+0.008
0.0109
183. 200
183.310
+O.llO
0.0600
183.200
183.160
-0.040
0.0218
366.400
366.520
+0.120
0.0327
366.400
366.240
-0.160
0.0437
11J4
The results show that from 9.16 mg to
can be determined
~ith
'66.~
fair aoauraoy by this method.
Photomicrographs were
aho~n
(magni:tioaticn, x240)
for the precipitate formed by direct method
precipitate
fo~n~d
mg of zinc
28
, for the
by using diammonium hydrogen phosphate
in the px·oposed method and for the precipitate obtained by
recommended procedure in Figures 12A, 12B and 12 C
respectively.
The photographs show that the particle aize
of the precipitate of recommended procedure was considerablt
improved due to elongated prismatic crystals compared to
the precipitate (fine prismatic crystals) formed either by
direct method or by ·the use of diammonillm hydrogen phosphate
in the routine procedure.
The sizes of the crystals are bigger
whe~
compared
to those formed by using diammonium hydrogen phosphate in
the routine procedure.
The sizes of the crystals formed
by recommended procedure are - the leagth 0. 080
1JI1!I
and
o. 048
mm
an.i
tha breadth 0. 032 mm for bigger orya"tals!
0.016 mm for smaller crystals.
crystals is about 80,
The
vi~al
peroent of smaller
The sizes of the crystals formed by
using dia.mmonium hydrogen phosphate in the
recommend~d
procedure are 0.016 mm length and n.OJ5 mm width and all
the
c:~:-ystals
are of tho same size.
The amount of zino in the filtrate at various pH
values (7.0 to 8.7) using zinc- 69 as a traoer are reported
in Table 21.
.
.
-
41'-_,..
..
~.
1U~
Determination of unpreoipitated zino using Zn- 69
1-
Zino in fil tn te
(mg)
pH
8.7
14.66
8.5
7. :u
8.3
2.92
8.1
1.09
7.8
0.02
7.6
o. 00
c.co
o.oo
o.o1
o.oo
7.5
7.4
7.2
7.0
----------------·--------------------------------·-----!rhe results show that amou.nt of zinc in the fil ti'IJte
between pH 7.0
l'ange
·r.o
and.
7.8 is almost nil.
to 7.8 is ideal fer qurmtitative preci,_;Hdion·
of zinc by this method.
at pH 9. 3.
Hence, the pH
Tho preoipite.tion usually IJOrnmenoes
Figu:r(l l3 is the graph of thE' pH of tht! <Jolution
against the amuunt of zinc in the Ziltrate.
The amount of zinc in the filtrate obtained
from reoomme.adsd procedure was also determined usinG
di thizonate metbod
Figure
14.
27
•
The oalibrt•tion au.rve is sho\'ill in
It is found that the loss of zino is 30
p&•
••r-------r-------,-------~--
~12
-.
~
E
,
-'
'
0
0
'
~
,
0
I
--r-,_ I
4
1
•
I
I
0
70
74
pH
Effect of pH
I)
•o
"
B2
7.8
on precipitation of
Zinc ammoniUM phosphate.
7 -- -
0.5.
.
0
fjt
/
//
-i
I'
~----t-
·------------··
;=~ ~~--~-' --j
.:0
concerd rct1cr
40
c• 7,rc
50
[j..:g)
Fig 14 · Calibration ct.~rve for determining Zinc
)'I
535nm.
..
1116
'
TABLE 22
Calibration
ou1~e
Volume of the
solution
(ml)
For
data for determining zino s-
pg
of Zino present
Opticl:ll.
denai ty
1.0
0.1.6
2.0
0.30
3.0
0.45
4.0
0.60
th~
filtrate,tbe optical density attained is 0.63
which corresponds to 30
p.g
of zinc.
Conoantration of ammonil.l.l'l.l aoe ta·te is orl. tioal
beoausa it cont:r:ols ·the pH of the aolu1iion.
If leas than
Cono".mtreti,ms of arnmouium !1o<3ta.te :from l5 - 50 mmoles
were a tlldied wi·th good ..:eaul ts.
in ·rable 23.
The
rt~::m.llis
are presented
1117
TABLE 2'
Effect of conoeatration of 111111110nium aoetate on the determination
of zinc ammonium phosphate ,_
Ammonium
acetate
taken
(mmoles)
pH
Zino
taken
Zino
found
Difference
Error
(mg)
(mg)
{mg)
(%)
2.0
8.4
7'3.280
76.580
... ,. 300
4.5030
5.0
8.2
73. 280
75.504
1'2. 224
10.0
e.o
73.280
74.742
+1.462
'· 0350
1.9950
15.0
7.7
73.280
73.875
-tO. 595
0.8119
20.0
7.4
73.280
73.280
o.ooo
0.0000
30.0
7.3
73.280
1'-'· 290
+0.010
0.01:57
40.0
7.3
T5. 280
73.296
+o.ol6
0.0218
50.0
7. 2
73.280
73.260
-0.020
0.0273
The resalts of the effect of the amount of
precipitant is shown in Table 24.
It is found that for
complete preoipitation of 1.12 mmolea of zinc, the reagent
required is l. 2 mmoles.
Concentration changes of disodium
hydrogen phosphate between the limits 2
P~d
10 mmoles
always yielded reproducible results, but concentrations
of the precipitant above 10 mmoles, produced higher values.
This might be iue to the
with sodium ions.
routine use.
conta~inaticn
of the precipitate
A value of 2. 5 mmolea was selected for
•
11J8
TA})L.E 24
Effect of exoese reagent on the precipitation of zino
ammonium phosphate a-
Zino teken
Zino found
Difference
Error
(mg)
(mg)
(mg)
( ")
l.!)
73.280
73.262
-o.ol8
0.0246
1.5
73.280
73. '-94
+o.ol4
0.0191
2. 5
73.280
73. 2fl0
o. 000
o.oooo
s.o
73.280
73.272
-o.oos
0.0109
10.0
73.280
73.312
+0.032
0.0436
15.0
73.280
74.282
+1.002
1. 3680
25.0
73.280
76.950
+3.670
5.0080
Na2 HPO
taken 4
( mmolE•s)
The effeot of foreign anions on the determination
of zinc ammonium phosphate was studied and the resu.l ts az·e
reported in Table 25.
The resul t!'l show that anions like
sulphate, nitrate, acetate and obloride when present upto
50 mmoles do not contaminate the precipitate when used as
their ammonium salts.
However, the same studies when conducted
using alkali salts clearly show higher values when the salt
concentrations exceed 10 ll'.llloles.
anions do not interfere in the
It can be concluded tru:.t
pre~ipitation.
It is the
alkali metal, that oontami•1atea the prscipi tate resu.l ting
higher values.
Sodium silioate interferes if present in
concentration above l IDII!Ole.
1()~
TABLE 25
Datel"mination of zino in presenoe or foreign anions
Subs tanoe
1-
Conoen tra tion
(mmo1es)
Za taken
(mg)
Zn found
..
25.0
73. 280
73.262
-o.ol8
0.0246
50.0
73.280
73. 29 2
+0.012
0.0164
4 No 3
25.0
73.280
73.204
-0.076
0.1037
50.0
73.280
7'3.200
-0.060
0.1090
NH4 01
25.0
73.280
73.294
•o.o14
0.0191
"
50.0
73.280
73.24-8
-0.032
0.0436
x 2 so4
5.0
73.280
73.482
+o. 202 0.2757
10.0
73.280
74. 290
+1.010
l. 3780
5.0
73.280
73.265
-0.015
0.0205
10.0
73.280
74.030
+o. 750 1. 0230
Na Cl
5.0
73.280
73.381
+O.lOl
0.1378
Na 01
1o.o
73.280
74.000
..-o. 120
0-:3824
5.0
73.280
73.232
-0.048
0.0655
10.0
73.280
73.481
..-o. 201
o. 2743
l.O
73.280
74.000
+O. 720
0.9824
(NH ) so
4 2
4
NH
..
•
Na N0
.
3
Na{ oH coo)
3
"
Na2
:uo 3
(mg)
Difference
(mg)
Error
( ~)
Results of precipitation of zino ammoaium phosphate
after preliminary separation of zino from cations {50 mg eaoh)
are reported in Table 26.
110
•
TABLE 26
Precipitation of zino
diverse oatioue
1-
ammonium
phosphate in preeenoe of
(50 mg eaoh)
Cation taken
Zinc taken Zinc found
(mg)
(mg)
Difference
(mg)
E~r
(")
Cu(II), Cd(II), Bi(III),
Hg(II), As(V), Sb(V) &
73.280
73.485
+O. 205
o. 2798
7"j. 280
73.248
-0.032
0.04'36
73. 280
73.424
+0.144
0.1965
73.280
73.182
-0.098
0.1338
Pb( II)
l'ii( II}
Ba(II), Sr(II), Ca(II),
Mg( II) and Mn( II)
Fe( III), Cr(III) and
Al( III)
Zinc was separated and determined in presence of copper,
cadmium, bismuth, mercUl7t arsenic, antimony and lead by
precipitating them as sulphides from hydrochloric acid
solu ticn.
Zinc was determined in presence of nickel after
complexing with ammonium tartrate and ammonium chloride.
Barium, strontium, c&.loium, magnesium and manganese 1o1ere
separated as their sparingly soluble phosphates and iron,
chromium and aJ.umiuium were separated as their hydroxides,
keeping
zinc in its soluble zinc ammonia complex.
Zino
was then determined in the filtrate by the proposed method
and fairly accurate results were o btaiDed.
11 t
Cadmium - 115 traoer wae used tor the ooprecipitation
studies.
About 26 percent of oadmium was ec1trained b7 zino
ammonium phosphate and hence the interference of cadmium in
this zino det-;.rmi.wtion 11!1 because of ooprecipi tation. The
results are presented in Teble 27.
TABLE 27
Co pre cipi te.tion of oadmium with zino ammonium pho ephate
Zino taken Cadmium tracer
taken
(mg)
( mg)
CadmiUlll carried
by- zino
(mg)
1-
" ot Cadmium
carried
73. 280
24-. 740
7.126
28.80
73.280
4-9.480
14-. 290
28.87
73. 280
74-. 220
21.300
28.70
73.280
98.960
28.190
28.4-8
73.280
123.700
34.880
28.20
Ridsdale' s analysed sample of Brass, B. c. s. No. 5:f'
was used for the application of the proposed method.
The
values obtained are in fair agreement with the reported
value, 24.2.
The results are shown in Table 28.
Figure 15 is the thermogravimetric aurve of zinc
ammonium phosphate.
The curve has a hortzo:~.tal line upto 160°0.
On i'urther heating, water and ammonia gradue.ll.y escape and finally
the pyrophosphate is formed quantitatively at 560°0.
Tom>-•rclur~,·c
r-----"'~'r'c_---,-----'T4~'c_---r----~'~'~'----
4 70
·--------.-------,
'
6
!
_ _J_
I
I
------·
- -t-------
I
Frg.IS. Thermogra'Yinetnc curvt
- ______L --- -'for
Z1nc ammonrum phosphate.
\
112
TABLE 28
B.c.s.
Determination of zino in Erae•,
Alloy taken
(mg)
Zino taken
calculated
No. 5f ,_
Zino found
Zino oontent
(mg)
( mg)
75.7
18.32
18.32
24.20
151.4
36.64
36.65
24.21
302.8
73. 28
73.28
24.20
605.6
146.56
146.62
24.26
( IC)
CONCLUSIONS
The simple new method described for the gravimetric
determination of zinc by precipitation from homogeneous solution
uses the volatalisation of ammonia procedure.
It is no doubt,
superior to the conventional methols with respect to crystallinity
of the precipitate and accuracy of the results.
tracer method that the
unp~eoipitated
It was found by
zinc in the filtrate is
almo:::t nil ancl by colorimetric method is 30 Ub•
The extent of
copreoipi tation of cadmium alongwi th zinc was found to be
28IC •
Nitrate caused no interference unlike in the conventional method.
The gravimetric factor Zn/Zn NH4Po • 0.36649 is also good when
4
compared to either Zn/Zn S04 • 0.40497 or Zn/Zn 0 • 0.80339.
This method found to applicable for the determination of zinc
in Brass.
---
113
RE:PERENCES
1.
J.H. Kanzelmayer, in "Treatise on Analytical Obemietry",
Eda., I.M.Koltho!! and P,J,Elving, Intereoiet!Oe Publiehera,
Lowlo:>n, "Part II, Vol. 3, P.l25 (1961).
1.2 1
2.
J,E:,Vanoe and R.S,Borup, Anal.Chem.,
610 (1953).
3.
N.C.Vosburgh, G.Cooper, w.J.Clayton and H.P.Pfann,
Ind.Eng,Chem.Ana1,Ed,, .!Q, 393 (1938).
R,Berg, Z,ana1.Chem,, ,ll 9 171 (1927).
5.
H.Funk and M.Ditt,
Ibid
., j!, 332 (1932).
6.
P.Ray and M.K.Bose,
Ibid
• , ,22, 400 (1933).
_u, l. (1897).
g, :na (1924).
K,Kraut, Z,anorg.Chem.,
z. anal. Cham.,
B.
G. Spaau,
g.
A.01assen,
10.
A.S.Whee1er, J.Chem.Soo., 31, 565 (1905).
11.
S.H.Simonsen and P.C.Kristopher, Anal,Chem., 26, 681 (1954).
12.
W.Mark We.rk and H,Gebhaardt, Z.anorg,Chem., 147 1 42 (1925).
Ibid
., ]:!!, 189, 3n (1879).
-
-
H. A. Fales and G.M.Wars, J,Am.Chem.Soc., ,!!, 487 (1919).
14.
C.Duval, "Inorganio Thermogravimetric Analysis", Elsevier,
New York, (1953) P. 277.
15.
G,E.F.Lundel1 and H.:Bee, Z,angew.Chem.,
16.
E. R. \.laley, L. Gordon and
o. A. Simmonds,
~~
II.617 (1915).
Ana1..-Chem.,
1060 (1950).
-
17.
H.:Plasohlta, Chemist.Analyst., 2, 44 (1955).
18.
D.H.K1ein and E.H.Swift, Talanta,
]1,
349 (1965).
~'
114
-
19.
R. B. Hahn and D. L. P.L'i~le, Anal. Ohim. Aate..
20.
W.Pilz, Mh.Ohem., §j, 471 (1952).
21.
E.J • .Nake.no, J.Chem.Soo.Japan Ind.Chem.Seot., .§1, 565 (1963).
22.
J.P.Jonea, O.E.Hileman and L.Gordon, Talanta, !Q, 111(1963).
23.
F.il.Firsohing and J.G.Bre1r1er, Anal.Ohem., ]2, 1630 (1963).
24.
S.Hikime and L.Gordon, Talanta,
25.
H. v. J)akin, z. anal. Chem. , ]2, 27'3 ( 190::>).
26.
A.I.Vogel, "A Text Book of Quantitative Inorganic Analysis",
.!! 1
, 31, 38 2 ( 1964).
851 (1964).
Longman, Green and Co.Ltd, London,(1968) P.433.
27.
G.Charlot, "Colorimetric Determination of Elements",
Elsevier, Amsterdam, (1964) P.432.
28.
Ref. No. 26,
P~
533.
---