D EPOSITED BY THE FACULTY OF
GRADUATE STUDIES AND RESEARCH
Mc.?C{ILL
UNIVERSITY
LIBRAR.Y
ACC. NO.
OATH
THE PREPARATION & PROPERTIES OF PURE
HYDPOGET~
PER.OXIDE
THESIS
A. C. CUTHBERTSON.
Presented in part fulf11~ent of the
requirements for the degree of ::raster
of Science.
McGil1 University
:tay, 1927.
-000-
This work has been carried out under
the supervision of Dr. O. Maass.
The author
desires to express his appreciation for much
helpful advice and criticism.
THE
PREPARATIO:~
AND' PROPERTIES OF PURE HYDRCG1N PEROXIDE
PART I
Introduction
The subject matter of this thesis deals with
the preparation of pure hydrogen peroxide and the subsequent use of this pure product for the re-determination
of the density End melting point, as well as the deter-·
mination of the partition coefficients of hydrogen peroxide between ether and water.
In connection
~ith
tte
latter, theories of solution are discussed.
The reas·on that the re-determinat ion of the
density and melting po.intwere attempted was because they
serve as the criteria of purity and the original values
did not appear to be sufficiently accurate for this purpose.
A number of determinations oOf the partition co-
efficients has been made by other workers between ether
and water, as well as other solvents, but the maximmn
concentration dealt with was only about 30 per cent. This
work deals with the whole range of concentrations.
'r.he. ofreparati~
'Of _oPur_~
H202'
- General Remarks
The preparation of pure hydrogen peroxide has
been published in detail so that only a short account need
be given here.
The pure product is now obtained by start-
ing with a 30 per cent. solution marketed by the Laurentian
Laboratories.
This unfortunately contains a great many im-
purities, both organic a.nd inorganic, as well as a fraction
-2-
of a per cent. of sulphuri'c acid.
Due to the presence
of the latter the raw product must first be distilled
in alkaline solution under vacuo at about
75°0.
The
distillate is an almost pure water solution of about 28
per cent.
This pure water solution of peroxide is then
concentrated under vacuo using as in the former case a
sulp~uric
acid pump which simultaneously evacuates and
absorbs the water vapour.
The principle of this pump
is exactly the same as the first with the exception of
its dimensions which are considerably sma.ller, but at the
same time it possesses a much larger absorbing surface.
Evaporation is carried on till a
75-80 per cent. solution
is reached, when in order to avoid serious losses it is
removed to a vacuum system where some of the peroxide and
most of the water are condensed in an ice salt bath leaving in the vessel a 98 per cent. solution of peroxide.
Three fractional crystallizations very carefully
carried out usually suffice to give a pure product.
The
estimation of the strength of the peroxide is carried out
with potassium permanganate in acid solution,
The llelting Point of Pure HZOz.
A permanganate titration was run giving a value
of 99.97 per cent. peroxide.
placed in the crystals,about
A Beckman thermometer was
~/5
of the mass being frozen.
-3A carefully corrected reading gave a value of
.89°0.
The Beckman thermometer was. standardized at 0°0. by placing it in supercooled water, freezing
sa~e
and noting the
height the mercury finally rose to.
The Density of H202 over the whole Temperature Range.
The dilatometer method was used for this determination.
To a bulb of about 6 c.c. capacity, a capillary
tube was sealed and. a scale from a broken Beckman thermometer was rigidly fastened to the tube, but of course was
80
fastened that it could be wasily removed for weighing
of the tube.
A bath of carbon dioxide and ether in an
unsilvered dewar could be kept constant by judicious stirring to 1/10 of one degree and the readings were taken with
the aid of a magnifying glass.
The tube was first calibrated with water..
'Va.ter
is preferable as it has the same type of meniscus as peroxide.
rIVat er was placed in the tube to a certain height,
weighed and the reading on the scale at a definite temperature was noted.
Five such readings were deemed sufffcient
for the purposes of calibration.
Knowing the volume of
water which could be obtained from the tables from tbe
weight, and also the number of scale divisions corresponding to these volumes the volume of one scale division is
obtained, and is equal to .001515
0.0.
The first attempt to accurately
density was most unsuccessful.
deter~ine
the
The di1atometer was made
-hI
of soft glass and the bulb was blown on the end of the
capillary tube.
It was only a moment after the peroxide
had been placed in the dilatometer that decomposition
made itself apparent to a very marked degree.
As the
tube had been very carefully cleaned the decomposition
appears to be due entirely to the glass surface.
Pyrex was then substituted and it was found
the decomposition could be considerably reduced especially
when tubing of the required size was sealed to the capillary tube, rather than blowing a bulb, as it appeared blowing a bulb strains the gla.ss.
A certain amOllnt of local
decomposition is probably due to point surfaces.
Hydro-
fluoric acid was run in and run out again as quickly as
possible in order to remove any points without actually
etching the glass.
It is difficult to say how success-
ful the method is and until more experiments are carried
out it is not to be recomr.1ended.
It must not be overlooked, however, that the
actual volume of gas is small.
So far as a capillary
tube is concerned it will nevertheless introduce a serious error in a reading.
The decomposition is so slight
relative to the weight of the peroxide that over a period
of 2 hours no change was noted in the weight.
The following method was used which (as will be
shown subsequently) was checked by actually measuring the
volume
as formed.
f
fter ~ei
1
I
rn
attaching t e
scale the tube was "mmersed On t e c rbon dioxide ethe
b tb
t
C.
The tube was ' llow ed to come to the temper-
ture of the b~th
took place.
uring whic
The bulb, now
was tapped caus"ng
t
time
slight decomposition
the temperature of the bath,
he trapped gas to rise and tlen t e
menisc s rea ing was imle iately taken.
e aCC1Jracy of this method was proven by t .1.e
follow'ng P oce ure.
e
i
ram in ica e
B
A
t1e met od .
-6-
The open end of the dilatometer (B) was attached by means of a flexible rubber tubing to one arm
(A).
of a manometer
A reading on the diIatometer scale
was taken and, then by raising the mercury level in the
other arm the pressure (measured by the difference in
height of the two arms)was applied to what bubbles were
present.
By means of a formula the
vol~rne
of the bubbles
at atmospheric pressure can be calculated and this volume
subtracted from the volume of the liquid at the height
the reading under
formula for the
at~·!lospheric
calcu~ation
pressure was taken.
The
of the volume of the bubbles
is deduced in the following way_
Let PI = atmospheric pressure
Let P2 = pressure applied when the mercury level
is raised.
Let~v~
= volume
n
Then
assu~ing
scale
R2
Now
V2 ::
"
= difference
--
"
If
in the two readings on the
volume of one division.
x
where RI
"
Baylets Law,
V2
Also VI -
of bubbles at pressure PI
reading at PI
=
If
Pl Vl
P2
n
P2
Vl- V2
= (RI
- R2 ) K.
-7-
VI -
PI V1
=
P2
or
VI (1 - PI
-
p~
':
(RI - R2) K
(RI - R2)
K
The values of the density of pure H202 are given
b-elow.
The tube was in all cases tapped.
A comparison
with Dr.Hatcher's figures is included, as well as the cal-
culated values from the equation for the curve.
Temperature
Density
Density
in 0C.
Experimental Calculated
1.4855
1.4791
-19·7
-13·5
-9·5
-4.9
-2·3
0.0
2.9
1.4619
1.4791
1. 474S
1.4701
1.4673
1.464-9
1.4619
1. 4~1b
1.454-41.4519
1.1+744-
1.4701
1.4669
1.4649
1.4569
1.4543
7·7
10.0
12.4
1.4.97
1.44-75
1.4455
1.443 0
1.440 3
1.4-33 1
11+.1
16.2
l~.O
20.4-
23·3
30 .1
32.2
34.0
1. 4309
1.42~~
1.4273
35·6
39.9
1·4g56
1.4232
1. J+t168
1·4500
1.44-79
1.4460
1.4435
1.4404
1.4333
1.4311
1.4290
1.4275
1.4231
The equation is D -
Difference
Hatcher's
Values
.,.. .0001
.0000
.,.. .0004
.0000
.,.. .0004.0000
.0000
-.0001
.,.. .0001
-r .0003
..,. .0003
.,. .0004
of-
.0005
1.4747
1.4693
1. 4669
1.4630
1.4596
1.4547
1.4520
1.44-92
1.44-76
1.4451
1. 443~
+ .0005
.,.. .0001
.,.. .0002
+- .0002
-r .0002
+ .0002
-.0001
1.4649-r.00105t
D
= density of pure H202
t
= temperatl1re
in oC.
In order to check the accuracy of the density at
zero the densities of peroxide solutions at zero were also
obtained and in this case the volume of gas ·was calculated
by means .of the formula above and the necessary corrections
applied.
The results are tabulated below.
t1!,
;'-
H2P2
Readings
Atmos.Pressure
Reading
9.7·02
96
101
104-·5
9497
!\~ean
93·61
Density
124- cm.
1.4-4~9
1.4486
1. 44~g
99
value for density
262.5
1.4320
270.0
26
1.431 9
1~ean
26~.O
.1
value for density
.0086
.0156
.021tt
1.44g~
267.9
26~.5
Vcl.of gas
in c. c.
1.431~
.0211
.0215
.0235
1.4319
The equation for this curve taking the density
at OOC. for 100 per cent. peroxide as 1.4649 is D
D
= density
A
=
~.
= .94~6~.005163A
peroxide
The fact that the density of H202 obtained by merely
tapping the tube agrees so far as the curve is concerned with
the
two
values obtained by the "pressure" method seems to
warrant accepting the value at OOC. correct to at least one
part in 7000.
-9-
THE PREPARATION AND
PROPERTI~S
PART
OF PUPE
~-ryJRC'\}~~:
PEROXIDE
II
The Distribution of H202 between Water and Ether.
Introduction
The dream of a universal solvent goes back to
the very beginning of chemistry and so far as the history
of the science is concerned is second only in importance
to the transmutation of metals.
"Solution" then, as now,
was shrouded in mystery and the early alchemist seemed to
think that if an explanation for it could be found a most
important step towards his ultimate goal would ensue.
Investigations on solutions today bear much the
same relation to chemistry as a whole that the search for
the universal solvent bore centuries ago to alchemy.
Theo-
ries of solution admit of little or no generalization.
We
can make the statement that "like dissolves liken but the
significance of it depends on whether or not we can determine the criteria of similarity.
The term solubility is one of wide scope, depending
on both the physical and chemical properties of the molecu-
lar species involved.
Surface tension, heat of solution,
change of volume on mixing of liquids, internal pressure
and polarity are all intimately connected and
inter~ependent
on what the solubility of one sUbstance in another may be.
A consideration of the number of factors involved and their
-10-
individua.l complexity make it at once evident that nothing
more than empirical relationships are to be expected.
It has been mentioned. above that a large nUlTIber
of factors appear to govern the solubility of any particular molecular species in another.
All these factors are
usually summed up in the expression molecular forces of
attraction.
Attractive forces exist between the molecules
of the solute, the solvent, and also between the solute and
solvent.
In other words in the simplest case of solution
the minimum number of attractive forces is three.
The system which was investigated deals with a
two phase three component system consisting of ·water, hydrogen peroxide and ether, i.e. the distribution of hydrogen
peroxide between water and ether.
The concentration of peroxide could be accurately
determined in each phase over tbe whole range of concentrations
and at two temperatures
25°0. and oOe.
For each temperature
of course time had to be allOVlred for equilibrium to be established before the concentration in each phase could be determined, and the results obtained are probably important because
they tend to show the complexity of the factors involved in
any heterogeneous equilibrium.
EquilibriQ~
is generally considered to belong to
one of two classes, viz. homogeneous or heterogeneous.
The
former is much simpler and lend.s itself fairly readily to
eit"':1er an experimental or theoretical approach.
It is defined
-11-
as an equilibrium confined to one phase, while the .latter,
i.e. heterogeneous is concerned with two or more.
The system to be described is obviously a case
of heterogeneous equilibrium and we define it in two ways.
The qualitative expression is known as the phase rule, while
the quantitative one is known as the distribution law. It is
with the latter that we are concerned here.
The first attempt at any sort of generalization
regarding the above is due to
from
~:1illia.m
Henry in 1905, when
on the equilibrium between a gas and its
ex~eriments
solution in a liquid he deduced that the mass of gas dissolved by a given volume of liquid was proportional to the
pressure of the gas for any given temperature, or expressing
it mathematically we have,
m
P
~
K,
m - mass of gas per c.c.
p
= pressure
K
a
constant for any
This equation can be
Let
of the gas
Cl -
eX~Tessed
te~,erature
in another form,
concentration of gas in
the liquid phase
= m grams per unit volume
Let
02 =
concentration of gas in the gaseous pha.se,
Substitution then gives
Cl
=
K.
This is the general
02
expression for the Distribution Law.
In
1~55
Bunsen subjected this law to a. rigorous
-12-
test and found it held quite accurately at moderate
pressures and these results were in turn verified by
later investigators.
In
l~72
Berthellot and Jungfleisch
continued the research on the system liquid - liquid
with reference to the partition of iodine between carbon
disulphide and water and pointed out that over the concentrations possible the law of· Henry could be satisfactorily
extended from systems gas-liquid to systems liquid-liquid.
Actually, however, the "Law of Henry" is strictly
applicable to either ideal gases or very dilute solutions
and many other investigators had noticed deviations from
this law which even from a theoretical point of view could
not be explained.
condit ion unt il
The matter remained in an unsatisfactory
~Ternst
showed thatr: deviat ions could be
partially explained by realizing the restrictions the very
nature of the problem imposes on the validity of the law.
Gases at high pressures - the partition of a third
substance at high concentrations bore no such simple relationships.
Nernst pointed out that substances behaved
~ifferent-
1y in different solvents regarding association, dissociation
and compound -formation and the law was therefore limited to
the statement that lithe concentrations of any single molecular species in two phases at equilibrium bear a constant
ra.tio to each other for a given temperature".
It is evident therefore that in order to obtain
-13-
a mathematically constant ratio for the
conoent~ations
in a system involving a heterogeneous equilibrium we must
know the following facts.
(1)
The extent of association in the phases.
(2)
The extent of dissociation in the phases.
(3)
The extent of compound formation.
( 4)
The ext ent of dissociation of the compound formed.
:Humber (2) refers to the partition of an electro~:umbers
1yte and can be eliminated in this case.
(1), (3) and
(4) may be met with in any system.
In a great number of cases, these factors would
be extremely difficult if not impossible to ascertain but
where such information is available, valuable facts concerning equilibrium can be ascertained.
Let a
t\~O
phase
system be considered in each phase of which an equilibrium
exists according to the following scheme:
---'~'"
"
,
NI Al"'-:~2 A +--:,;-_u. ~:l AI""'" :,1
2
t
A2'
A1, A2, A1,
NIl !:2'
Ni,
A' -1-- ....••
2
2
represent mo 1 ecu1 ar species and
and N~" represent the stoichiometrical coefficients,
re~resent
the concentrations of these
molecular species in the one phase at equilibrium and
and
82
the concentrations in the second phase.
61 e2 a{
The mass
law equations for these equilibria will be:
enl
1
,
C~2
,
C{nl C·2 n2
=
K
a,nd
cnl
1
,
Cl'nl
n
c2 2
O
'n2
2
--
Kl
-14-
Each of these molecular species is distributed between the
two phases, which fact is represented by a series of distribution ratios.
-
=
c'2
er2
=
By division of the first two equations an equation results:
K
Kl
--
~l
1
~2
K!ni
K n2
1
2
t
1
2
This equation shows that knowing the equilibrium
constants in one phase and the distribution constants of all
the known molecular species the equilibrium constant in the
second phase can be calculated.
If the distribution ratio is to be constant a most
important assumption is made, viz. that the two liquids are
insoluble in each other, or do not have their mutual solubility affected by the distribution of the substance.
This
condition, of course, is never realized either from the standpoint of the insolubility of the two: liquids themselves or
the mutual solubility not being effected by the presence of
a third substance.
If the distributed phase aotually lowers
the solubility of the two liquids it is probable it may at
high concentrations reduce it to a negligible amount.
On
the other hand the distributed substance may increase the
solubility to a considerable extent and in such a case there
-15-
is more and more tendency for the
and a true solution results.
t~o
layers to disappear
In such a case the par.t''ition
coefficient will gradually drop, until at consolute concefttrations the ratio is unity. Considering the problem from
this point of view then, only when the distributed phase
is present in infinitely small amounts can we expect no
effect on the mutual solubility.
In other words, the dis-
tribution law can only successfully be used. when the concentrations are very dilute.
The term dilute is a function of
the system under consideration because the lowering or iner-easing of the mutual solubility is dependent on the characteristics of the two liquid phases a.nd on the distributed
Therefore for a given substeJnce, it may be
substance.
capable of much greater concentrations than another without
greatly affecting this mutual solubility.
Hydrogen peroxide appears to increase the mutual
solubility of the water and ether to a marked degree and
some experiments were carried out
mn
just this effect.
If
one ands alcohol to an ether water solution it takes much
less alcohol (about
1/5) to produce miscibility of a
52.5~
solution of peroxide and ethpr than in the case of ether and
water alone.
This indicates that the process of reaching
consolute concentrations has been increased by the peroxide
and that in this case the quantity of alcohol
to
is
complete it, i.e., make the distribution unity less/than
re~lired
in the case where no third component was originally present.
-16-
In this c.a.se a closed tube v.:i th a magnetic stirrer was used
and small quantities
0:
the absolute alcohol were added by
means of a burette fitted through the cork.
~
The experiment
was intended only for rough comparative pur;oses and no
quantitative data are available.
It might be well to mention here that certain
fa.ctors govern the choice of a system for in\restigation.
They are as follows:
(1)
Ease of determination of the distributed substance.
(2)
Concentrations can be varied over wide limits.
(3)
Purity of
materia~s.
In the first place accurate volumetric estimation
can be ma.de by using standard potassium permanganate in acid
solution.
For dilute ethereal solutions difficulty was ex-
perienced in titrating because of lack of a definite end
point.
In order to overcome this difficulty a definite
large volume of the ether layer was placed in a flask fitted
with a, trap and the ether was boiled off under reduced pressure, after which the residue wa.s titrated.
Secondly hydrogen peroxide is miscible with water
in all proportions so that concentrations from 1 to 100 per
cent. could be obta.ined.
Thirdly water and ether are compar-
atively easy to obtain in a pure state while the method of
preparation of peroxide leaves little doubt that in this
connection it compares favoura.bly with either of the former •
D.e.
®
The apparatus used in this connection was extremely
si~ple,
the diagram being almost self-explanatory. Earlier
investigators like / a.lton and Le is shook a mixture of hydrogen peroxide water end ether in glass stoppered bottles at
a constant temperature.
able as peroxide
Sh0~S
This iO.ea was not consi ered advisa distinct tendency to decompose at
ground glass surfaces and in order to minimize this difficuI ty an ent irely different idea was used.
A glass tube (A) about 16 cm. long and 2.5 cm. in
diameter was drawn out to
th~
diameter of the neck of a 250 c.o.
-18-
graduated flask. T,his neck
W2"S
sealed on providing a means
of having the tube closed with a tightly fitted glass stopper.
At the bottom and about
~
cm. from the bottom capillary tubes
(F) we.re sealed in the tube (A).
a glass stirrer was inserted
Eefore the bottom wa.s sea.led
cons~.sting
of three glass spirals
spaced about 4 cm. apart and to the top of which a
light~ron
nail enclosed in a glass tube was sealed.
The liquids were stirred, at a constant temperature for
about an hour by means of a magnetic stirrer. Around the neck
of the tube as indicated in the diagram a
solenoid(~} bell
wire was placed, connected in series with a bank of lamps.
In parallel with the solenoid a. circuit breaker (C) was connected to raise and lower the stirrer.
stirrer (E)
~Hcts
The movement of the
in this way made dependent on the periodic
variation of the current in the solenoid and not in the actual
making and breaking of the circuit.
It was found c four litre beaker (D) filled with
water could satisfactorily control the temperature to onetenth of a degree with the judicious use of a bunsen flalJle end
stirring the water continuously with air.
The experimental procedure was as follows: An aqueous
solution was poured into the tube till its level was about that
where the second capillary tube we.s sealed in • On top was placed
an equal volume of ether which had been purified by washing,
standing over calcium chloride and subsequent distillation,
after sodium he.d been
da.ys.
allo\~'ed
to react for some two or three
Rubber tubes fitted with glass plugs were placed over
-19-
the ends of the capillary tubes and. the glass stopper put
in place.
The mixture was stirred at
~constant
temperature
when after an interval of one to one and one-half hours
equilibrium was reached.
Portions of each phase were then
r-emoved in the following manner.
A hollow ground glass tube
was inserted in place of the stopper after attaching a
rubber tube to it.
The liquid layers were then blown out
through the capillary tubes into
25 c.c. specific gravity
bottles, the first portions in ecch case being neglected.
A definite volume of each layer was then titrated, or if
one c.c. of the layer required too large a quantity of
permanganate then one c.c. was diluted to
25 c.c. in a
graduated flask and a definite volume of the dilute solution was titrated.
In order to reduce errors to a minimum
the same pipette was used for both layers.
In order to obta.in concordant results one of the
most important things noted was the efficiency of the stirring.
A stirring stroke of
5 cm. usually suffices but in any case the
interfacial layer between the two phases must be continually
broken.
Probably the main reason for care in this direction
lies in the fact that peroxide solutions, especially those of
higher
concentrations~
are much heavier than ether.
This pre-
caution applies equally well when diluting a sample of the
layer to a known volume.
Vigorous stirring is necessary to
ensure homogeneity.
The results obtained in the experiment are expressed
-20-
in mol fractions of hydrogen peroxide per c.c. of the
original water and ether layers obtained in the following
way.
~[ol-fraction
no.of c.c.KMn04- per unit volume x K
=
Uol. wt. of H202
=
C.
c.
K~.~n04
per c. c. layer x .0042~7
34
Temp.
Water
Mol. fraction
Ether
.0351+4-
.01890
.03227
.02952
.013 1 4-
.02900
.02282
.016~9
.01573
.01194
.009416
.009374-
.005106
.004709
.004166
.002~3g
.001934.001231
.0005090
-.0002571
Grms. per c. c.
Water layer
Partition Coefficient
.01563
.01261
.008gS0
.02410
.01053
.005930
.001442
• 9850
.002531
.0013~5
·3220
• 001 324-
.0005~73
.0004097
.000353 0
.0002062
.0001252
.00007017
.00003 0 70
.00001525
Mol. fraction
Ether
.03740
1.205
1.097
1.0030
· 7700
·5744.5134
.4061
.005294.004610
Temp.
Water
25°C.
.0241g
.01023
·3115
.1697
.1610
.1415
.09650
.0657S
.04186
.01731
• COg·74
1·~7
2.06
2.23
2·30
2.57
3·19
~:~~
6.95
7.06
10.95
11·55
11.82
13·73
15·42
10.13
16·55
16.~3
OoC.
Grms. per c. c.
Aqueous layer
1.2740
.• 8213
.002846
.0009394
·35S3
.2016
.0001540
.04902
Partition Coefficient
-20a-
Ct/rve s X.% TlI
~
,C'\
o
:z:: -
o
()
())
o
~A TU I'... t c5 ° C.
@ I'-..O L0 .)0 0 lIeS ~ I >0 laic.
CD TtM F
~ T tM r t~AT ~ ~ t
I\@
(Doe.
~:\
~~
~ >~~ ~
""
~ ~\ ~
~
(l +
~
~ ~ t--
;--..
'-
/
1-/
r
~
\:7
0 .1
0-2
0 -3
0·4
G~ A M 0
112. 02.
0 -5
Pt ",
0 -6
0 -7
0 ·8
0 ·9
1-0
1-1
1 c.c_
A Q., UtOU 0
L Ayt "'-.,
l -~
1-2.
e
tJ /-V ("
6
0
tu
()t
,
;s=
o
1/
r
/
0
0
f\>
ID
T U f"-.
t
-
@ TtN rt"'-.A ru,,-
t
-
T t Af t
~A
o'e
c..ye.
(D
0
Q
/
-
t-- -~
~
/
/
~
/Iij
~
9)
V@
~.
V
~
(0
0-0
0-000:)
hi. () L
0-01
r~ A CTI
0-01.5
O -Oc
0/11 0
ft"'-- cc-
ODI::5
AG...-UtOU:)
000
0-036
LAY t "'--
-21-
Temp.
l~oC.
N. De Kolossowsky, Bull. Soc.Chim. 4me.Ser.Tome 37 •
.. 0000518
• 0'')07194• 0011 514
.0000856
.0016376
.000 1 300
.002223g
.0026626
.0038937
.0001932
.0002421
.0003821
.001+9528
.0005456
.00071 56
.0059249
.007 4557
.0010620
• 001 5103
.0090157
.0244
.0414-
.0557
.0756
.0902
.1417
.1684
.2015
• 2530
·3°65
13.~~
13·~
12.60
11·51
11.00
10.19
9.08
8.28
7·02
5·97
Discussion of Results
It is at once evident that them partition coefficients show no constancy in value.
The first part of
the curves I, 11, III, drop quite sharply with a later
tendency to become almost horizontal to the x axis at higher
concentrations.
It would appear had Kolossowsky worked
through the whole range of concentrations his curve would
have been between I and lIT for higher concentrations.
For very dilute solutions the curves I, II and
III all show a slight bend but without actually determining
values for concentrations of the order of .1 and
.05 per
cent. we are not justified in assurning that they become
asyntotic to the x axis.
If any generalization regarding the distribution
law is possible it appears to be at high concentrations and
seems to represent not the distribution of hydrogen peroxide
between water and ether
but rather the distribution of
-22-
water
bet~een
hydrogen per,oxide and ether and" of course for
almost 100 per cent. peroxide we really have en infinitely
small .amount of water present.
The general shape of Curve IV tends to bear out
this idea.
The first part of the curve might be considered
as representing the distribution of
th~
last part the distribution of the water.
peroxide while the
Of course, at
very high concentrations we really have the question of
the solubility of hydrogen peroxide in ether as the predominating factor.
The impossibility of making any quantitative
predictions about such a system is easily made evident.
In
the first place even water and ether are by no means immiscible and we have seen that the distributed perexide
increases this solubility
so
that one of the basic assump-
tions for obtaining the distribution law cannot be realized.
Therefore the extent of the deviations for any system will
partly at least depend on the deeree of mutllal solubility
of the two phases as well as the influence of the distributed
subs~ances
on it.
Besides this we have to deal
wit~the
number of
molecular species which are in equilibrium with one another.
The partition coefficient as ordinarily determined is not
the ratio of the concentration of a molecular species in
one laye"r to the concentration of the same molecular species
-23-
in another but rather a mean of a number of them in each
layer involving probably three or four equilibria.
Henry's Law as pointed out by :'Ternst does not
deal with such cases.
~e
have reason to believe that per-
oxide possesses considerable additive power and shows a tendency to associate and therefore introduces new molecular
species but a quantitative determination of them is almost
impossible.
Due to the distinct differences of water and ether
this additive power is different for each phase so that if
the mass law constant for the water complex = KI
of the ether
K2-
=K2
KI is either less
tr~n
and that
or greater than
In the sruae way the degree of association is probably
largely dependent on the solvent.
Due to the fact that accurate qua.untitative data
have not been obtained for this system the mathematical
exp.ressions for these correction fa.ctors have been purposely omitted.
The question still remains as to whether it is
possible in this system to make any qualitative predictions
about the distribution of peroxide and offer an explanation
for the observed facts.
A consideration of the polarity of
liquids seems to be the only way.
The basis of the idea of polarity is that the
field of molecular forces of attraction do not necessarily
-24-
proceed from the centre of the molecu.les but may be concentrated in one part of it, i.e. in one of the atoms composing
the molecule.
Such a molecule which is not surrounded by a
symmetrical field of force is called a polar molecule.
It would now be in place to consider to which of
the two classes of substances the
under discussion belong.
com~onents
of the system
Surface tension and heat of vapor-
ization have always been looked upon as giving one some idea
of the forces of attraction in liquids.
The more strongly
the molecules are held together the more energy is required
either to form a new surface or separate them from one
In the case of water and peroxide the surface ten-
another.
sions of the pure sUbstances and their solutions are to all
intents and purposes the same.
much less.
In the ca.se of ether very
In other words, we will call water and peroxtde
polar sUbstances and eiher) either a slightly or non-polar
substance, the distinction being one of degree tatber than
kind.
It is at once evident from the foregoing that the
attractive forces between water - water molecules:
forces between peroxide peroxide mols
=
attractive
attractive forves
between water peroxide molecules and that any of these forces
are greater than the forces acting between ether
cules.
ether mole-
As mentioned above, the criteria of "likeness" must
be defined.
From this point of view the degree of "likeness"
or similarity means the degree of polarity and when we say
-2~..;
"like dissolves like" we mean that polar substances dissolve
polar substances.
We assume then we are justified in assuming that
the components of this system fall into two distinct classes.
In the case of hydrogen peroxide and water the physical constants of these sUbstances tend to point to xhe fact that
their fields of force are not symmetrical and that the degree
of unsymmetry is approximately the same.
Ether falls in
the other class, ·viz. its physical constants point to symmetrical fields of force and it is therefore a representative
of that group· of substances
kno~n
as non-polar,
Let us now consider an aqueous solution of hydrogen
peroxide from a kinetic point of view.
Both water and per-
oxide molecules are cor..tinually freeing themselves from the
main body of the liquid and since all three sets of attractive
forces in the liquid (as menti;Jned above) are nearly" equal
the chances of either a water or a peroxide molecule returning
is also about the same.
If we place over this solution pure
ether then both these types of molecules will bombard the
ether layer.
For dilute solutions of peroxide it will be chiefly
the water molecules wnich will be doing this
~nd
the chances
are the few peroxide molecules which do enter are not very
likely to come near to one another.
As however the concen-
tration is increased there becomes a preponderance of hydrogen
peroxide molecules escaping into the ether layer.
NOW, we
-26-
should not expect large attractive forces to be exerted between ether and peroxide or of water but at high concentrations
there must be sufficient numbers getting into the ether phase
to make it possible for them to come in contact with one
another and, ha.ving no great attraction for the solvent eth.er,
they tend to be attracted to themselves forming aggregates
of molecules in that phase.
The extent ef aggregation is not
necessarily directly proportional to the number of peroxide
molecules entering the ether phase as the curves indicate.
Once these aggregates are formed it will be much more difficult for it to return to the water phase because the larger
a molecule becomes the more difficult it will be to force
itself between
th~ st~ongly
attracted waterk!1'..ole-cules.
As a result the tendency appears to be for them to
remain in the ether layer.
Thus, the increase of peroxide
in the ether layer causes the concentration per unit volume
to increase and in turn continues to decrease the ratio of
concentrations in the two layers.
The additive power of peroxide must not be entirely
overlooked.
It shows much more tendency to form addition
compounds than water and although polarity plays an important
part, loose molecular aggregates with ether are by no meass
improbable, but this does not invalidate the statement that
aggregates do fo.rm; rather it helps to confirm it.
~e
are now in a. position to sum up the attractive
forces in the system from a standpoint of their relative
magnitude.
-27-
Let TI W represent the attractive forces existing
between water -water molecules.
P P the forces between peroxide
peroxide molecules.
W P the forces between peroxide water molecules.
E E the forces between ether
eth~r
molecules.
E W the forces between ether water molecules.
E P the forces between
et~er
peroxide molecules.
From surface tension measurements and tbe fact
that peroxide is miscible ir.. all proportions of v:ater we
can write
~w
I'
=
••
p p
=
p
~.Y
The forces E E must be small in comparison for
it does not require much energy to separate them from one
another.
i.'!;ater and ether are for this purpose considered
to be immiscible.
Hence it is evident forces W E are less
than E E.
Peroxide and ether are fairly soluble and as we
assumed that from a purely physical point of view the degree
of polarity is about the same, the additive power of peroxide
must account for the difference,
greater than w
I.
P.E forces appear to be
T:'"
..:2J.
vVe then have the following qualitative relationship:
7!
1~~
.1
= P W
-
'0
.I.
P
>
ZE
>
P E > E ~.~.~
It is to be noted that P E is considered to be
greater than E i,".·.
If peroxide and water exhibit a.bout the
same degree of polarity then we should expect approximately
the same solubility for both.
To explain these differences
compound formation has to be resorted
t~
and as pointed out
above is probably quite justified.
An alternative explanation would be that surface
tension measurements are not sufficiently indicative to
allow a decision to be made.
The determination of the di-
electric constant which is looked upon as being one of the
important physical constants in so far that a high value
usually indicates polarity, will probably help to decide
which point of view is correct.
So far as this system is concerned we cannot satisfactorily apply the distribution law due not only to the
lack of knowledge of the equilibria existing between the
molecular species concerned, but also because the partition
of a third substance profoundly affects the mutu.al solubility of the phases between which it is distributed.
-29-
REFERENCES
Bulletin de la Societe Chimique
1925·, 4 me Ser. Tome 37.
Recherches sur le Phenomene de Part age par Nicolas De
Kolossowsky
Ostwald Van't Hoff.
Vol. XXXVIII.
~oer
Zeitschrift fftr
Physikalische Chemie,
die Akalisa1ze des Hydroperoxyds in
Wasseriger losung, van Harry Thornton Calvert.
American Chemical Society Journal,
Vol.~,
Pt.I, 1916.
The Partition Coefficients of Hydrogen Peroxide between
Water and certain Organic Solvents.
Reference Books
Hildebrand - Solubility
Colloid Symposium !:!ono.graph, Vol. II, 1924.
Part I
Introduction
The
Point of Pure H2 0 2 •
Density of H2 0 2 over the whole Temperature Range.
~elting
(a) Experimental methods employed.
(b) Values obtained
(1) Experimental
(2~ Calculated
((3
Hatcher's Values, J.A.C.S. Vol.XLII,Fo.12,Dec.l920.
4 Verification of the Value obtained at ooc.
Pa. rt II
The Distribution of H202 between Water and Ether
Introduction
Theoretical Considerations of the Distribution Law.
Experimental Procedure.
The Values obtained for the Distribution of H202 between
water a.nd ether at 0° and 26?
A Comparison with Kolossowsky's Figures at 18° with Curves.
Discussion of the Results.