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An investigation of the physical properties of concentrated solutions of sodium sulphate

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AH IHVE STIGATIOH OF
THE PHYSICAL PROPERTIES OP CQHCEHTRATED SGLUTIOHS
OP SODIUM SULPHATE
A Thesis
Presented to
the Faculty of the Department of Chemistry
University of Southern California
In Partial Fulfillment
of the Requirements for the Degree
Master of Sciences
by
Donald C. Stewart
June 1940
UMI Number: EP41520
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UMI EP41520
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T h is thesis, w r i t t e n by
....
u n d e r t h e d i r e c t i o n o f h%.3.. F a c u l t y C o m m i t t e e ,
a n d a p p r o v e d by a l l its m e m b e r s , has been
p r e s e n t e d to a n d a c c e p t e d b y t h e C o u n c i l on
G raduate S tu d y and Research in p a r tia l f u l f i l l ­
m e n t o f the re q u ire m e n ts f o r the degree o f
MASTER OF SCIENCE
D ia n
Secretary
Da/e....J.UNE.I— -1,9-40--
Fa c u lty Com m ittee
Chairm an
TABLE OP CONTENTS
CHAPTER
PAGE
I INTRODUCTION TO THE PROBLEM ......................
1
II EXPERIMENTAL DETERMINATIONS ......................
3
Preparation of the Solutions Studied
.........
3
Purity of the s a l t ...........................
3
...........................
5
Making up the S o l u t i o n s ......................
5
.............................
5
V i s c o s i t i e s ......................................
12
Electrical Conductivities ......................
15
...............................
.22
III DISCUSSION *OF R E S U L T S .............................
27
Assay of the Salt
Specific Gravities
Surface Tensions
Specific Gravities
.............................
27
Discussion of the Viscosity Results . . . . . .
33
Discussion of C’onductivity R e s u l t s ...........
36
Discussion of Surface Tension Results . . . . .
38
IV SUMMARY AND. CONCLUSIONS
........................
41
LIST OP TABLES
TABLE
I.
PAGE
Hydrometer Corrections at Various
Temperatures .............................
II*
8
Specific Gravities of Concentrated
Sodium Sulphate Solutions at Various
Temperatures •
III.
9
Coeffieients of Viscosity and Times
of Efflux of Water at Various Temp­
eratures
IV.
.............
13
Coefficients of Viscosity and Times
of Efflux of Concentrated Solutions
of Sodium Sulphate at Various Temp­
eratures
V.
.............
14
Specific and Equivalent Conductances of
Concentrated Aqueous Solutions of Sodium
Sulphate at 25.0 and 35.0 Degrees
Centigrade
VI.
• • • . • • • • • • • • . •
20
Surface Tensions of Concentrated Solu­
tions of Sodium Sulphate at 25.0 and
.
35.0 Degrees C e n t i g r a d e .............
VII.
24
Equations Expressing the Relationship
Between the Specific Gravity and Temp­
erature (T) in Degrees Centigrade for
the Six Solutions Studied
• • • • • « •
29
ii
TABLE
VIII.
PAGE
Comparison of the Observed and Calcu­
lated Specific Gravities at Various
Temperatures of the Six Solutions
Studied
IX.
•
...................
30
Equations Expressing the Relationship
Between Specific Gravity and Normality
of Concentrated Solutions of Sodium
Sulphate at Certain Temperatures
X.
...........
31
Comparison of the Observed and Calcu­
lated Pecific Gravities of the Concen­
trated Solutions of Sodium Sulphate
Studied . . . . . . . . . . .
................
32
XIST OP FIGURES
GRAPH
I.
PAGE
Change of the Specific Gravities of
Certain Cone entrated Solutions of
Sodium Sulphate with Temperature » * * * *
II*
10
Change of the Specific Gravity of
Concentrated Solutions of Sodium
Sulphate with Normality at Certain
Temperatures * * * * * * * * * -* * * •
III*
**
11
**
16
**■
IV
**
21
**■
25
Change of the Coefficients of Viscosity
of Certain Concentrated Solutions of
Sodium Sulphate with Temperature * • *
■XV.
Change of the Coefficients of Viscosity
of Concentrated Solutions of Sodium
Sulphate with Normality at Certain
Temperatures * . * * * - *
V.
. • . * ♦ . *
Change of the Specific Conductivity of
Concentrated Solutions of Sodium Sul­
phate with Normality at 25*0 and 35.0
Degrees Centigrade * * , . * • # . . •
VI.
Change of the Surface Tension of Concen­
trated Solutions of Sodium Sulphate
with Normality at 25*0 and 35*0 Degrees
Centigrade . * * * * * * . * * . *■ *■ *
VII.
Change of the Specific Gravities
of
11
GRAPH
PAGE
Concentrated Solutions of Sodium
Sulphate with Concentration at Various
Temperatures
(International Critical
Tables d a t a } * * . * * « « * * * * « * * *
VIII.
28
Chang© of the Coefficients of Viscosity
of Concentrated Solutions of Sodium
Sulphate with Concentration at Several
Temperatures (Glass and Madgin, 1934) * *
DIAGRAMI*
•
-
34
-
Equipment used in determining the
Electrical Conductivity of the Solutions
of Sodium Sulphate Studied • * * * * * *
19
CHAPTER I
In t r o d u c t i o n
to
tee
problem
It has hean found that the effects produced in a
liquid by a dissolved salt may be expressed mathematically
only for very dilute solutions— as the concentration
increases, it becomes increasingly difficult to forecast
the value of any of the solution constants without resort­
ing to actual measurements.
Due to this fact— that these
physical properties must be measured in dilute solutions if
generalizations are to be made— it is found that such
measurements h§ve been made an exceedingly high degree of
refinement for dilute solutions, but that in the ease of
most salts, such values are very infrequent for more con­
centrated liquids.
The chemical engineer, however, deals
with concentrated solutions almost exclusively, and has a
very real need for a usable set of constants relating to
their properties.
The present study was undertaken to help satisfy this
need and considers certain physical properties of highly
concentrated solutions of anhydrous sodium sulphate.
It
follows a previous study made at this University^ by Mangold
on concentrated solutions of sodium carbonate.
1 G. B. Mangold.
California, (1937)
Sodium sul-
Thesis, University of Southern
phate was chosen because of its importance in many fields
of chemical manufacture,
The extent of this use is indicated
by the fact that the consumption of it in the United States
approximates some 300,000 tons yearly.
In making a study of this type, it seems advisable
to set up certain criteria for the experimental work.
These
may be summarized as:
(1)
The properties measured should be those
actually of value to the chemical engineer.
(2)
The methods of measurement used and the values
obtained should be directly applicable to
industrial situations.
(3)
The values obtained should be accurate, although
not necessarily to the meticulous degree
required by the physical chemist seeking to
investigate new phenomena.
With these factors in mind, it was decided to deter­
mine the following properties of a series of highly con­
centrated ,solutions:
(a)
specific gravities over a consid­
erable temperature range (20° - 100°0);
(b) viscosities over
the same approximate temperature range;
(c) electrical con­
ductivities at several temperatures; and (d)
at several temperatures.
surface tensions
CHAPTER II
. EXPERIMENTAL DETERMINATIONS
I.
PREPARATION OF THE SOLUTIONS STUDIED
Purity of the salt,
A quantity of Baker's C. P,
grade anhydrous sodium sulphate was obtained and oarefully
dried at 110°C,
The following tests were then made, using
the methods recommended by Murray
(a)
Insoluble matter —
Five tenths gram of the salt
was dissolved in one hundred cubic centimeters of distilled
water and filtered.
No residue could be observed in the
liquid or upon the filter paper, indicating the absence of
any insoluble matter.
(b)
Moisture —
dried and ignited.
found.
A portion of the salt was carefully
A weight loss of 0.41 per cent was
This was well within the range specified by Murray
and was accepted as satisfactory, since the salt was to be
put into solution in any case.
(c)
Chlorides —
One gram of the salt was dissolved
in twenty cubic centimeters of water.
A few drops of nitric
acid and a few drops of silver nitrate solution were then
added.
The solution remained clear, indicating the absence
of chlorides.
B. I. Murray.
Standards and Tests for Reagent and
C. P. Chemicals.
Second Edition (1927)
(d)
Nitrates—
One gram of the salt was dissolved
in twenty cubic centimeters of water.
A few milligrams of
sodium chloride, a drop of indigo solution and ten cubic
centimeters of sulphuric acid were then added and the
mixture shaken,
The blue color did not disappear, indica­
ting that nitrates were absent.
{e)
Ammonium salts —
One gram of the salt in
twenty five cubic centimeters of water was treated with
Kessler's solution.
A negative test was obtained,
since the
solution showed no change in color.
(f)
Heavy metals —
One gram of the salt in twenty
cubic centimeters of water saturated with hydrogen sulfide
gas.
No precipitate formed, indicating that the salt was
free from heavy metals.
(g)
Magnesium —
One half gram of the salt was dis­
solved in twenty cubic centimeters of water.
A few drops of
ammonia solution were added, followed by a few of an
ammonium phosphate solution.
The solution showed no change,
indicating the absence of magnesium salts.
(h)
Arsenic —
One gram of the salt was mixed with
four cubie centimeters of a stannous chloride solution and
allowed to stand.
The solution showed no change in color,
indicating a negative test for arsenic.
Assay of the Salt — ■ Making up the Solutions.
The
dried salt was assayed for its sulphate content hy precipi­
tation of the sulphate "by barium chloride as recommended by
?
Fales .
An average of three determinations gave 99.89 per
cent sodium sulphate.
This was considered satisfactory,
and the salt was used without further purification.
Six solutions were made up.
Attempts were made to
have them approximately 1.0 1, S.O 1, 3.0 E, 4.0 E, 5.0 E,
and 6.0 E.
The last three solutions were highly super­
saturated at room temperature, and it was found impossible
to get the sixth solution much more concentrated than the
fifth.
The solutions were analyzed by the barium precipi­
tation of the sulphate as before.
Eo attempt was made to
bring the solutions to exact normalities, due to the
difficulties of standardization.
Values for exact normal­
ities may be obtained from the graphs made from the data
collected.
IX.
SPECIFIC GRAVITIES
The more accurate methods for determining specific
gravities are doubtlessly those employing the pycnometer or
the Westphal balance.
The use of either of these pieces of
apparatus at temperatures above 40°0. offers considerable
_________
___
H. A. Fales.
Inorganic Quantitative Analysis
difficulty,
ao they were rejected for use in the present
study in favor of the hydrometer method, since specific
gravities up to the boiling point were desired for the
solutions under consideration.
Corrections for hydrometer readings are necessary if
they are used at temperatures deviating from the calibration
temperature, due to the effect of expansion or contraction
of the glass.
These corrections may be obtained with a
fair degree of accuracy by measuring the specific gravity
of water with the hydrometer at the temperatures to be used,
and comparing these observed values with those determined
by other methods^.
These corrections will hold if the
density of the liquid studied is not too radically differ­
ent from those of pure water.
Corrections for the hydro-
a
meters used in this work were obtained in this manner, and
these corrections are given in Table I.
The hydrometers used read to 0.005 degrees of
specific gravity, but a reading to 0.001 degree could be
estimated quite readily.
In making the readings the solu­
tion studied was placed in a hydrometer tube in a water bath
at the chosen temperature for a period of fifteen or twenty
¥
minutes.
The tube was kept stoppered during this time to
,3 International Critical Tables of Numerical Data*
McGraw Hill & Co., New York for National Research Council.
1926-30;
3:26, Density of water.
7
prevent losses from evaporation.
In the meantime, the
hydrometer was placed in the water hath and allowed to come
to temperature.
The tuhe was unstoppered, the temperature
of the contents eheeked to he certain that it was the same
as the hath, and the carefully dried hydrometer was placed
in the solution.
The hydrojneter reading .was taken and the
temperature measured and recorded.
The thermometers used
read to 0.1 degree Centigrade.
Several check readings were made at each temperature
hy removing and replacing the hydrometer and allowing it to
again come to equilibrium.
The observed and corrected
readings are given in Table II.
Graph I shows the change
in the specific gravity with increasing temperatures for
each of the six solutions studied.
Graph II shows the
effect of increasing concentration upon the specific grav­
ities of sodium sulphate solutions at certain temperatures.
8
TABLE I
HYDROMETER CORRECTIONS AT VARIOUS TEMPERATURES
im;... .
... ■■■■
Correct
spec, gravity
of water4
Temper­
ature
Observed
spec, gravity
of water
23.0°C.
0.998
0.99756
0.000
30.0
0.997
0.99567
- 0.002
40.0
0.995
0.99224
- 0.003
50.0
0.991
0.98807
- ,0 .003
60.0
0.987
0.98324
- 0.004
70.0
0.984
0.97781
- 0.006
75.0
0.982
0.97489
- 0.007
80.0
0.979
0.97183
- 0.007
85.0
0.977
0.96863
- 0.008
98.0
0.970
0.95981
- G .010
International Critical Tables.
Hydrometer
Correction
3:26
4 International Critical Tables of Numerical Data.
McGraw Hill & Co., New York for National Research Council
1926-30.
3:26 Density of water.
9
TABLE II
SPECIFIC G R O T T Y OF CONCENTRATED SODIUM SULPHATE
SOLUTIONS AT YAHIGUS TEMPERATURES
Temperature
Observed
Reading
Corrected
Reading
Solution I (1.0101 N)
23.IOC
30.0
40.0
50.0
60.0
70.0
75.0
80.0
85.0
98.
1.058
1.057
1.054
1.050
1.046
1.041
1.039
1.034
1.032
1.024
1.058
1.055
1.051
1.04 7
1.042
1.035
1.032
1.027
1.024
1.014
Solution III (3.0220 N)
21.400
30.0
40.0
49.2
59.0
70.1
73.0
80.0
84.0
91.0
1.174
1.171
1.167
1.161
1.156
1.151
1.150
1.146
1.144
1.141
1.174
1.169
1.164
1.158
1.152
1.145
1.143
1.139
1.136
. 1.132
Soluti on V (4 .9854 N)
30.0°C
39.9
49.0
57.1
70.2
72.7
79.2
84.0
90.2
1.272
1.269
1.264
1.261
1.252
1.251
1.247
1.245
1.238
1.270
1.266
1.261
1.257
1.246
1.245
1.240
1.237
1.230
Temperature
Observed
Reading
Corrected
Reading
Solut ion II (1 .9831 N)
23.1°C
30.0
40.0
50.0
60.0
70.0
75.0
80.0
85.0
98.
1.113
1.111
1.107
1.102
1.097
1.094
1.092
1.088
1.085
1.080
1.113
1.109
1.104
1.099
1.093
1.088
1.085
1.081
1.077
1.070
Solution IV (4 .0090 N)
30.2°C
40.0
49.6
58.8
71.0
73.0
80.2
83.0
92.0
1.221
1.218
1.214
1.210
1.203
1.201
1.196
1.195
1.190
1.219
1.215
1.211
1.206
1.19 7
1.195
1.189
1.187
1.181
Solution VI (5 .1005 N)
30.1°C
39.3
48.8
58.0
70.0
71 .4
79.1
83.0
90.0
1.280
1.277
1.272
1.269
1.262
1.261
1.256
1.253
1.250
1.278
1.274
1.269
1.265
1.256
1.255
1.249
1.246
1.241
10
Specific
Grav
iiiiiiiiiiiiiiiit
Illlim il lllllll!!!!!!!!::
jS H H in illim i i f f l fflH
1.30C
1.24C
iaEBniiiiiiiiiiiiliESi:
1.18
1.12
iUssisiiiiniiii:::::::::::
1.000 iiiiiiiiiiiiiiisiiiinii::::
iiuuuuuiiiiiiiE nn];:::::::::::::::::::::::::::::::::::::::::......
GRAPH I
Change of the Specific Gravities of Certain Concentrated
Solutions of Sodium Sulphate with Temperature
THE A. LIETZ
CO., SAN FRANCISCO
HO.
1.060
GRAPH II
Change of the Specific Gravities of Concentrated Solutions of
Sodium Sulphate with Normality at Certain Temperatures
III. VISCOSITIES
The Ostwald pipette method of determining solution
viscosities vms used in the present study.
The instrument
used was standardized b y ‘determining the times of efflux of
water at the various temperatures to be studied.
These
values and those for the absolute coefficients of water are
given in Table III.
A water bath was set up as in the work on specific
gravities.
In making the determinations the viscosimeter
containing 5.0 ml (measured with the same pipette in all
cases) of the liquid under consideration was placed in the
bath for fifteen or twenty minutes to reach the temperature
desired.
The solution was then drawn up into the capillary
arm and allowed to run back in the usual manner,
the time
of efflux being measured with a high grade stop watch
graduated to the fifth of a second and allowing estimates to
one tenth of a second.
A simultaneous reading of the temp­
erature of the bath was made.
The times of efflux were
measured a number or times for each solution at each temp­
erature and an average of the best values used
the calculations.
in making
The times of efflux and the calculated
coefficients of viscosity for the six solutions studied
are given in Table IV.
k International Critical Tables of Numerical Data.
McGraw Hill & Co., New York, for National Research Council.
1926-30.
5:10 Coefficients of Viscosity of water.
13
TABLE III
COEFFICIENTS OF VISCOSITY AND TIMES OP EFFLUX
OF WATER AT VARIOUS TEMPERATURES
Time of efflux
Coefficient of
Viscosity 5
22.5° C
1 minute , 39.7 seconds
0.00949 poises
23-0
1
38.5
0.00938
35.0
1
20.1
0.00721
50.0
1
02.9
0.00549
75.0
45.6
0.00380
97.0
35.5
0.00293
98.0
35.0
0.00290
34.2*
0.00284
Temperature
100.0
*Estimated.
^ International Critical Tables of Numberical Data*
MoGraw Hill & Co., Hew York for National Research. Council.
1926-30.
5:10
Coefficients of Viscosity of water*
14
TABLE IV
COEFFICIENTS OP VISCOSITY AND TIMES OP EFPLUX
OP CONCENTRATED SOLUTIONS OP SODIUM
SULPHATE AT VARIOUS TEMPERATURES
Temperature-
Time of Coefficient
efflux of viscosity
Solution I (1,0101 N)
2 3 .0°C
35.0
50.0
75.0
97.6
1 ’ 56.8"
1 29 .3
1 09 .3
49.5
39.5
0.01165
0.00849
0.00638
0.00414
0.00344
Solution III (3.022© N)
23.0°C
35.0
50.0
75.0
100.
2'
2
1
1
51.2"
10.8
36.6
07.4
52.3
0.01893
0.01382
0.00988
0 .00648
0.00499
Solution V (4. 9854 N)
3 5 .0°C
50.0
75.0
98.0
3*
2
1
1
22.0"
23.5
34.8
10.1
0.02319
0.01597
0.01009
0.00737
Temperature
Time of Coefficient
efflux of viscosity
Solution II (1.9831 N)
23.0°C
35.0
50.0
75.0
98.0
2 1 19.6”
1 46.4
1 21.2
56.9
45.2
0.01466
0.01066
0.00789
0.00529
0,00416
Solution IV (4.0090 N)
23.0°C
35.0
50.0
75.0
100.
3'
2
1
'1
1
36.2"
40.2
57.8
18.9
00,8
0.02493
0.01767
0.01259
0.00805
0.00607
Solution VI (5.1005 E)
35.0°C
50.0
75.0
98.0
3'
2
1
1
33.2"
31.2
35.7
11.5
0.02462
0.01692
0.01024
0.00761
15
The change of the coefficients of viscosity with
temperature of the solutions is shown in Graph III.
The
change of the coefficients of viscosity of sodium sulphate
solutions with increasing concentration at certain temper­
atures is shown in Graph IV.
The data for this figure
were taken from Table IV and the previous Graph.
The density figures for the standard liquid, water,
were taken from the International Critical Tables7 .
The
density figures for the six solutions studied were taken
from the previous section of the present work.
IV. ELECTSICAL CONDUCTIVITIES
The electrical conductivities of the six solutions
studied^ were measured by means of the Wheatstone bridge
method.
Diagram I indicates the equipment and circuit
employed.
The use of a thermostatically controlled water bath
equipped with a motorized stirrer permitted temperature con­
trol to 10.05 degrees Centigrade.
The electrical conduc­
tivities of the first five of the sodium sulphate solutions
employed were measured at 25.0 degrees Centigrade, but the
sixth crystallized out at this temperature and could not be
used.
The conductivities of all six solutions were
measured at 35.0 degrees Centigrade.
7 International Critical Tables of Numerical Data.
McGraw Hill & Co*, New York for National Research Council.
1926-30.
3:26 Density of water.
Coefficients
of Vis
16
0.0240
liuiiiMitui
0.0200
u iiian in in s ::::::::::::::::
i l l ! 1!!!! ! !!!!!:!!!:;;;;::= :
0.0160
0.012
0.0080
5 £1005 B
429854
S
VI
5
5
|0090 B
s
|0200 B
1*9831 B
0.004
1-0101 K
Temperature (°C)
GRAPH III
Change of the Coefficients of Viscosity of Certain Concentrated
Solutions of Sodium Sulphate with Temperature
Coefficients
of Viscosit
0.0240
0.0200
0.0160
0.0120
NO. 909-A
iixiiiiiiaiiiiiiiiiiisaSiilii!
THE A. LIETZ
CO., SAN FRANCISCO
0.0080
0.0040
0.0
3.0
N O R M A L I T Y
b.
GRAPH IV
Change of the Coefficients of Viscosity of Concentrated
Solutions of Sodium Sulphate with Normality
at Certain Temperatures
18
The electrodes of the conductivity cell were plating
ized before use as recommended by Findlay8 *
The water used
in preparing the 0*02 Normal solution of potassium chloride
used in determining the cell constant, was distilled in a
special all-glass still.
The specific conductance value of
the potassium chloride solution was taken from the Inter­
national Critical Tables8 for calculating the cell constant.
In making the determinations the conductivity cell
was placed in the water bath for twenty to thirty minutes
before any readings were made.
The values given represent
the average of a number of different readings obtained by
changing the variable resistance in the one arm of the
bridge, and redetermining the new point of balance on the
slide wire.
The calculated values for the specific and equivalent
conductivities of the six solutions studied at 25.0 degrees
Centigrade and 35.0 degrees Centigrade are given in Table V.
The change in the specific conductivities of these solutions
with increasing concentration is indicated in Graph 1,
8 A. Findlay, Practical Physical Chemistry. 4th Edition
8 International Critical Tables of Numerical Data.
McGraw Hill & Co., New York for National Research Council.
1926-30.
6:234
Conductivity of 0.02N K O I .
19
DIAGRAM I
EQUIPMENT USED IN DETERMINING THE ELECTRICAL CONDUCTIVITY OP
THE SOLUTIONS OP SODIUM SULPHATE STUDIED
A* D r y Cells
E. Kohlrausch slide wire
B. Microphone hummer
P. Single contact key
C. Type B Washburn Conductivity
Cell
G,
Pour dial resistance
box
D. DeKhotinsky type water bath
with stirrer
H.
Telephone Receivers
20
TABLE VI
SPECIFIC AND EQUIVALENT CONDUCTANCES OF CONCENTRATED
AQUEOUS SOLUTIONS OF SODIUM SULPHATE AT 25.0
AND 35.0 DEGREES CENTIGRADE
Concentration
Specific Conductance
Equivalent
conductance (A)
25 »0°C
1.0101 N
1.9831
3.0220
4.0090
4,9854
0.04797 mhos
0.07549
0.09292
0.10053
0.1U342
47.5 mhos
38.1
30.8
25.1
20.8
35 •0°C
1.0101 N
1.9831
3.0220
4.0090
4.9854
5.1005
0.05854 mhos
0.09247
0.11432
0.12563
0.13079
0.12918
57.9 mhos
46.6
37.5
31.4
26.2
25.3
JETZ
CO.. $44
'HAN Cl SCO NO. 90C-A
21
iiiiliiiiiiiiiiiiiBiiiiiiiiiieiiiiiiiiiiiiiaii
GRAPH V
Change of the Specific Conductivity of Concentrated
Solutions of Sodium Sulphate with normality
at 25.0 and 35.0 degrees Centigrade
22
V. SURFACE TENSIONS
The capillary rise method10 was used in determining
the surface tensions of the solutions studied.
The diameter
of the capillary of the instrument used was determined at
25.0 degrees Centigrade and at 35.0 degrees Centigrade by
measuring the rise of a purified benzene solution as recom­
mended by Reilly, Rae and Wheeler^-0 .
The surface tension
and density values for benzene used in calculating the
capillary diameter were taken from the International
Critical Tables1 1 ’ 1 ^.
The capillary and the containing vessel were care­
fully cleaned before each determination by using cleaning
solution, distilled water, alcohol and ether in the order
named.
Glass walled water baths were used to expedite the
reading of the capillary heights.
The temperatures were
controlled to ±0.1 degrees Centigrade.
In making the determinations, the solution to be
studied was placed in the containing vessel and the latter
was immersed in the water bath and left twenty to thirty
minutes to come to temperature.
The capillary tube was not
10 Reilly, Rae and Wheeler, Physico-Chemical Methods.
11 International Critical Tables of Numerical Data.
McGraw Hill & Co., New York for Rational Research Council.
1926-30. 4:4
Surface Tension of Benzene.
^
.IMSL*«
3:29,33
Densities of Benzene
23
lowered into the solution until the readings were to he made.
The walls of the tube were wet with the solution by foroing
the liquid up and down by varying the air pressure on the
side arm of the containing vessel.
The reading was then made,
and rechecked several times by forcing the liquid up and down
and allowing it to come again to equilibrium.
The surface tensions of the four least concentrated
solutions of sodium sulphate used were determined at 25.0
degrees Centigrade.
The two more concentrated solutions
crystalized out at this temperature.
The surface tensions
of all six solutions were determined at 35.0 degrees Centi­
grade.
The surface tensions measured at these two temper­
atures are given in Table VI.
The change of the surface
tension with concentration at these two temperatures is
given in Graph V I •
The solutions used were re-analyzed and the new
normalities used in making Table VI and Graph VI.
24
TABLE VII
SURFACE TENSIONS OF CONCENTRATED SOLUTIONS
OF SODIUM SULPHATE AT 25.0 AND
35.0 DEGREES CENTIGRADE
Surface Tension •
(in ergs/cm^)
Concentration
25.0°C
35.0°C
1.0192 N
78.17
80.02
1.9939
78.96
80.50
2.9098
79.73
81.12
3.9760
82.00
81.81
5.0543
-
84.87
5.2292
85.95
Surface Tension
A. LIETZ
CO, SAN FRANCISCO
NO. 900-A
::»»»:>tsi
GRAPH VI
Change of the Surface Tensions of Concentrated Solutions
of Sodium Sulphate with Increase in Normality.
At 25.0 and 35.0 degrees Centigrade
CHAPTER
III
DISCUSSION OF RESUITS
I,
SPECIFIC GRAVITIES
The literature contains considerable information
regarding the specific gravities of concentrated solutions
of sodium sulphate solutions for temperatures up to 40.0
degrees Centigrade, although fewer figures are available for
higher temperatures.
Only a few of the references will be
mentioned, due to their number.
The International Critical
Tables1 contain some fifty additional titles.
The Critical Table figures are a symposium of the
best values of a number of authors.
Some of these figures
are given in Graph VII for comparison with those found in
the present work and given in Graph II.
It will be seen that
the change of specific gravity with temperature is practi­
cally linear on both graphs.
Equations for the specific gravity-temperature curves
given in Graph II were calculated and are given in Table VII.
Table VIII gives a comparison of the figures actually
observed with those calculated from these equations.
It will
1 International Critical Tables of Numerical Data.
McGraw Hill & Co., N e w York for National Research Council.
1926-30.
3:81
Specific Gravity of Sodium Sulphate Solutions
27
be seen that the differences are well within the limits of
experimental error, since the hydrometers used were only
calibrated to 0,005 degrees of specific gravity.
Similar equations were also calculated from the data
used in making Graph III, which shows the change of the
specific gravities with concentration at certain tempera­
tures.
These equations are given in Table IX, and a com­
parison of observed and calculated results for this
phenomena is given in Table X.
Here, again, it will be seen
that the differences are within the limits of accuracy of
the experimental method used.
G i b s o n ^ h a s made some very precise determinations
for the specific gravities of sodium sulphate solutions for
temperatures up to 40.0 degrees Centigrade.
He concludes
that the salt is highly hydrated in lower dilutions at
lower temperatures— this effect being lessened by increase
in either temperature or concentration.
In the later work
he also determined the specific volume of the solutions
studied, and calculates the fietive volume of the sodium
sulphate in the solution.
He found no decided change in the
specific gravity at 32.383 degrees Centigrade, the accepted
2 Gibson, Special Report, Geophysical Laboratory,
Washington (1900)
3 Gibson,
Jour, Physical Chem., 31:496 (1927)
GHAPH YII
Change of the Specific Gravity of Aqueous Solutions of
Sodium Sulphate with Concentration at Various Temperatures
(International Critical Tables)
29
TABLE VII
EQUATIONS EXPRESSING THE RELATIONSHIP BETFIEEN THE SPECIFIC
GRAVITY AND TEMPERATURE (T) IN DEGREES CENTIGRADE
FOR TEE SIX SOLUTIONS STUDIED
Solution
Equation
I
Specific Gravity = 1.0607 - G.00G048T - Q.Q000045T2
II
= 1.1225 - 0.000376T - G.000QG19T2
III
= 1.1861 - 0.000551T - G.G0000053T2
IV
= 1.2210 + 0.000106T - 0.0000061T2
V
- 1.2813 - 0.000255T - ©.OOOOG35T2
VI
= 1.2832 - G.000057T - 0.0000047T2
30
TABLE ¥111
COMPARISON OF THE OBSERVED AND CALCULATED SPECIFIC
GRAVITIES OF THE SIX SOLUTIONS OF SODIUM SULPHATE
STUDIED AT CERTAIN TEMPERATURES
Solution
Observed Calculated
Reading Reading
Solution
1.058
1.112
1.171
1.0575
1.1118
1.1707
------
—
•-
—
—
-
I
II
III
IV
V
VI
60.0°C
I
II
III
IV
V
VI
1.042
1.093
1.151
1.205
1.257
1.263
1.020
1.074
1.132
1.182
1.230
1.241
1.051
1.104
1.164
1.215
1.266
1.274
1.0490
1.1047
1.1629
1.2164
1.2670
1.2736
80.0°C
1.0405
1.0945
1.1514
1.2052
1.2572
1.2630
90.0°C
I
II
III
IV
V
VI
Calculated
Reading
40.0°C
25.000
I
II
III
IV
V
VI
Observed
Reading
1.0194
1.0738
1.1303
1.1826
1.2318
1.2373
I
II
III
IV
V
VI
1.027
1. 081
1.139
1.189
1.240
1.248
1.0285
1.0833
1.1403
. 1.1917
1.2439
1.2482
31
TABLE IX
EQUATIONS EXPRESSING TEE RELATIONSHIP BETWEEN SPECIE10
GRAVITY AND NORMALITY (N) OE CONCENTRATED
SOLUTIONS OE SODIUM SULPHATE
AT CERTAIN TEMPERATURES
Temperature
25.0°C
Equation
Specific gravity
1.0030 + 0.054N + G.00049N2
40.0
0.9892+ 0.06GN
- 0.00083N2
60.0
0.9845+ 0.056N
- 0.00031N2
80.0
0.9710 + 0.058N
- G.00064N2
90.0
0 . 9 6 0 6 + 0.059N
- 0.00093N2
32
TABLE X
COMPARISON OB' OBSERVED AND CALCULATED SPECIFIC GRAVITIES
OF TEE CONCENTRATED SOLUTIONS OF SODIUM
SULPHATE STUDIED AT CERTAIN TEMPERATURES
Temperature
Observed
Reading
Calculated
Reading
Temperature
Solution I
(1.010. N)
23.1°C
30.0
40.0
50.0
60.0
70.0
75.0
80.0
85.0
98.
1.058
1.055
1.051
1.047
1.042
1.035
1.032
1.027
1.024
1.014
1.174
1.169
1.164
1.158
1.152
1.145
1.143
1.139
1.136
1.132
1.0572
1.0552
1.0516
1.0470
1.0421
1.0352
1.0318
1.0281
1.0241
1.0128
23.1°C
30.0
40.0
50.0
60.0
70.0
75.0
80.0
85.0
98.
1.270
1.266
1.261
1.257
1.246
1.245
1.240
1.237
1.230
1.113
1.109
1.104
1.099
1.093
1.088
1.085
1.081
1.077
1.070
1.1128
1.1095
1.1045
1.0989
1.0931
1.0869
1.0836
1.0802
1.0768
1.0675
Solution IV
(4 .0090 N)
1.1741
1.1691
1.1633
1.1568
1.1517
1.1450
1.1431
1.1387
1.1372
1.1317
30.2°C
40.0
49.6
58.8
71.0
73.0
80.2
83.0
92.0
1.2704
1.2655
1.2604
1.2553
1.2465
1.2443
1.2392
1.2352
1.2298
Solution VI
(P .1005 N )
1.278
30.1°C
1.274
39.3
1.269
48.8
1.265
58.0
70.0
1.256
1.255
71.4
1*249
79.1
1.246
83.0
1.241
90.$
Solution V
(4.9854 N)
30.0°C
39.9
49.0
57.1
70.2
72.7
79.2
84.0
90.2
Calculated
Reading
Solution II
(1.9831 N)
Solution III
(3.0220 N)
2 1 .4°C
30.0
40.0
49.2
59.0
70.1
73.0
80.0
84.0
91.0
Observed
Reading
1.219
1.215
1.211
1.206
1.197
1.19 5
1.189
1.187
1.181
1.2186
1.2154
1.2113
1.2061
1.1977
1.1962
1.1903
1.1878
1.1793
1.2773
1.2738
1.2691
1.2641
1.2562
1.2551
1.2493
1.2461
1.2401
33
transition point between the solid anhydrous salt and the
decahydrate.
at this point.
Other authors have claimed to obtain a change
Ho such change was observed in the present
work.
II.
DISCUSSION OF THE VISCOSITY RESULTS
The earlier literature dealing with the viscosity of
sodium sulphate solutions is cited in the International
Critical Tables^.
Here, again, the values given range only
to 40.0 degrees centigrade.
c
A recent publication by Glass and Madgin
gives data
which very thoroughly covers the 25 to 40 degrees Centi­
grade range.
Their values for these two temperatures are
graphed in Graph VIII for comparison with Graph V of the
present work.
These quthors express their results relative
to the viscosity of water at the temperature studied, neces­
sitating conversion to the corresponding coefficients of vis­
cosity to give directly comparable curves.
It will be seen
that in both cases concentration increases in the higher
normalities produce greater effects than in the lower dilu­
tions.
This conclusion was a l s o •reached by Tigerstedt, "The
4 International Critical Tables of Numerical Data.
McGraw Hill & Co., New York for National Research Council.
1926-30. 5YI5 Viscosities of Sodium Sulphate Solutions
5 Glass and Madgin,
J. Chem. Soo., (London), 1124, (1934)
34
Coeffi
of Vi
( in
0.02
iiiliiillii!!!!:
iiiiillHHEi
0.024
0.02
CO. 900-A
0.01
THE A. LI ETC
CO., SAN FRANCISCO
0.012 SEiiiilf iS ilU K
0.006
.0
270
Gram Moles Sodium Sulphate per 1000 grams Water
GBAPH VIII
Change of the Coefficient of Viscosity of Aqueous Solutions of
Sodium Sulphate with Concentration at Various Temperatures
(Glass and Madgin, 1934).
relative viscosities of sodium sulphate solutions increases
more rapidly than the concentration6 .
This effect is
especially noticeable in the lower temperatures, being much
less discernible at 75.0 or at 98.0 degrees Centigrade.
It
is an effect that is rather difficult to explain on the basis
of salt hydration if we accept Gibson's statement that the
degree of hydration is less at higher concentrations.
The
higher proportion of unionized slat present in the more con­
centrated solutions may offer the answer.
Attempts were made to graph temperatures against the
logarithms of the coefficients of viscosity as found in the
present work and given in Table IT*
This was done to see if
the curves of Graph IV are logarithmic in nature.
A similar
attempt was made to graph the logarithim of the temperature
against the coefficient of viscosity and the logarithim of
the concentration (from Graph V) against the coefficient of
viscosity at a given temperature.
Hone of these investi­
gations indicated that any readily discernible logarithmic
relationship held between these variables.
There is no evidence in the present work of any part­
icular change at the temperature corresponding to the trans­
ition point between the solid decahydrate and the anhydrous
6 Tigerstedt, Soe* Sci. Fennica Comment*
Math., l;No. 5 (1922)
Physico-
36
salt.
Hartshorns7 and Matsui and Oguri8 , however, found
breaks in their viscosity curves at 32.55 and 32.5 degrees
Centigrade .respectively.
These workers both used the same
type of apparatus and the same techniques.
They worked
with saturated solutions at all times, determining their
rates of flow at various temperatures.
against the temperature.
their curves.
This time was graphed
Glass and Madgin found no breaks in
In both their case and in that of the present
work the solutions used were not necessarily saturated at all
times, although they were probably saturated or even super­
saturated when some of the readings were made.
III.
DISCUSSION OS' CONDUCTIVITY RESULTS
Very little information is available in the literature
regarding the electrical conductivities of concentrated
solutions of sodium sulphate.
The Critical Tables9 give
equivalent conductivity values of 50.3 at 18.0 degrees Centi­
grade and 91.1 at 50.0 degrees Centigrade for a one Normal
solution.
A single value of 39.6 at 18 degrees Centigrade is
also given for a two Normal solution.
This last is in fair
N . H . Hartshorne, An apparatus for the Viscosimetric
determination of transition points, J. Chem. Soc., London,
1 2 5 ;2096 (19 24)
8 M. Matsui and S. Oguri, Determination of transition
point by the viscosity method, J. Soc. Chem. Ind. (Japan),
32:43 (1929)
Chem. Abs. 23;4874.
9 International Critical Tables, 6:231
ductivities of Sodium Sulphate Solutions
1926-30
Con­
37
agreement with 38.1 at 25 degrees Centigrade as determined in
the present work for a 1.983 Normal solution.
The agreement
for the one Normal solution is not as satisfactory.
In the
present work a value of 47.5 at 25 degrees Centigrade and
57.9 at 35 degrees Centigrade was determined for a 1.010
Normal solution.
Heydweiller3-^ obtained 50.7 and 40.0 at
18 degrees Centigrade for 1.0 Normal and 2.0 Normal solutions
respectively.
Study of Graph V, which shows the change of the
specific conductivity of concentrated solutions of sodium
sulphate at 25.0 and 35.0 degrees Centigrade, would indicate
some rather general conclusions.
As would be expected, the
specific conductivity increases with concentration.
The
amount of this increase is less at the higher concentrations,
and this is explained by assuming that the proportion or
ionized sodium sulphate under these conditions will be less,
due to purely mechanical crowding, if for no other reason.
This, of course, would mean a comparatively small increase in
the conductivity with increase in normality in the very con­
centrated solutions.
As a matter of fact, the graph would
almost seem to indicate that at extremely high concentrations
the conductivity is actually lessened (for solution VI over
solution V at 35 degrees Centigrade).
This value, however,
-1-® Heydweiller, Zeit. anorg. allg. chem., 1 1 6 :42 (1921)
38
roust not be taken too seriously, as solution VI was highly
supersaturated at this temperature and may have been slightly
crystallized.
The second effect noted from the conductivity data is
that the increase in specific conductivity due to increase
in temperature seems to.be more pronounced at higher concen­
trations.
Here again, this phenomena can probably by
explained on the basis of a change in the relative propor­
tions of ionized and unionized salt present.
IV.
DISCUSSION OH SURFACE TENSION RESULTS
The values reported in the literature for the surface
tensions of concentrated solutions of sodium sulphate are
tabulated below:
Temperature
Concentration
Surface Tension
Reference
0.5 molal
76.96 ergs/cm.^
Inter. Grit.
Tablesll
10
0.5
75.58
20
0.5
74.11
20
1.0
75.48
30
0.5
72.54
30
1.0
73.91
1.0 Normal
76.54
1.0
G r ., 1.0849
71.88
74.99
0°G
G
30
18
Sp.
18
Sp. Gr.,
11, 12, and 13.
1.1188
75.52
See next page
Morgan &
Bolel2
S t o c k e r ^
39
Stocker obtained his values by studying oscillating
jets of the solution.
drop method.
Morgan and Bole employed the hanging
Their data is somewhat limited, but they obtai
obtained the expression:
(Surface Tension)^ = 76.54 - 0.1553-t
for a noe Normal solution.
This would give a value at 25
degrees Centigrade of 72.66 ergs/cm.2 as compared to a
corresponding value of 78.17 in the present work.
Comparison of the above table with the values found
in the present work indicates that the latter are all much
too high.
The only explanation of this seems to be that
the capillary rise method is not suitable for working with
highly concentrated solutions due to crystallization effects
in the capillary tube.
Curiously enough, however, no
particular difficulty was found in making the determinations.
A further contradiction in the data collected is that
the surface tension apparently increases with temperature.
The only possible explanation for this phenomena would lie
in the possibility that the salt is in a different mole­
cular configuration at 25.0 degrees Centigrade than it is at
H International Critical Tables of Numerical Data.
McG-raw Hill & Co., N e w York for National Research Council
1926-30. 4;465.
Surface Tensions of.Sodium Sulphate Solutions
3-2 Morgan and Bole,
Jour. Amer. Chem. Soc., 35:1750 (1913)
13 Stocker, Zeit. fur Physik. Chem. 94:149.(1920)
35.0 degrees Centigrade.
plausibility,
This has some slight degree of
since the transition point of 32.5 degrees
Centigrade between the anhydrous salt and its decahydrate
is claimed by some workers to be a point of a similar change
for many physical properties of concentrated solutions of the
salt.
The surface tension values found in the present work
should doubtlessly be disregarded, due to their wide diver­
gence from similar values determined by other experimental
methods.
CHAPTER IV
SUMMARY AND CONCLUSIONS
(1)
The densities of a series of six solutions of
sodium sulphate varying in concentration from one to five
normal have "been determined over the approximate temperature
range of 20 to 100 degrees Centigrade.
Equations relating
the density to the temperature have been derived from the
data collected for each of the solutions studied, and equa­
tions relating the density to the concentration at certain
temperatures have also been computed.
The values found in the present work agree quite well
with those previously reported, and extend the available
figures somewhat, particularly for temperatures above 40
degrees Centigrade.
The change in the density of the solu­
tions studied with temperature was practically linear,
although there was some apparent tendency for a more pro­
nounced density decrease per unit of temperature rise at the
higher temperature.
(2)
Values have been determined for the coefficients
of viscosity of the same series of sodium sulphate solutions
and are in good agreement with those already reported.
Available figures have been extended considerably,
since none
have hitherto been reported for temperatures above 40 degrees
Centigrade.
42
The decrease in the coefficient of viscosity per unit
of temperature increase is quite definitely more pronounced
at higher temperatures.
The change of the coefficient of
viscosity with normality is much more pronounced at lower
temperatures than it is at higher temperatures.
(3 )
The specific and equivalent electrical conduc­
tances of the same series of concentrated sodium sulphate
solutions have been determined at 25 and at 35 degrees
Centigrade.
siderably,
The values found extend the available date con­
since solutions up to five normal concentration
were considered in the present work, whereas no previous
figures could be found for solutions more concentrated than
two normal.
The agreement of the values found in the present
work with the very fragmentary values previously reported for
one and two normal solutions was only fair.
The change of the specific conductance with concen­
tration is quite rapid for the lower concentrations, but
becomes much smaller as the concentration approaches three or
four normal.
Some slight evidence of an actual decrease in
the specific conductance was found between the 4.9854 and the
5.1005 normal solutions at 35 degrees Centigrade.
The latter
solution, however, was very highly super-saturated, and this
apparent decrease in the specific conductance may have been
due to crystallization of part of the salt.
43
(4)
Values have been determined for the surface
tensions of a series of highly concentrated sodium sulphate
solutioh?, hut they are in very poor agreement with those
previously reported.
This variance has been attributed to
the capillary rise method used in making the determinations,
and it has been concluded that this method is unsatisfactory
for making this determination on concentrated salt solutions,
due to errors produced by crystallization in the capillary tube*
(5)
No sharp break© were found in the density-tempera­
ture or the viscosity-temperature curves of the solutions
studied.
This is of interest in view of the fact that several
authors report such a change at 32.5 degrees Centigrade, the
transition point between solid anhydrous sodium sulphate and
its decahydrate.
Other authors deny the existance of any
change in these properties at this point, and the present
work would seem to corrobate this latter view.
BIBLIOGRAPHY
BIBLIOGRAPHY
Daniels, J. H. Mathews and J, H. Williams, Experimental
Physical Chemistry.' McGraw Hill Book Company, Ne w York
Second Edition, 1934
Pales* Harold A., Inorganic Quantitative Analysis, The
Century Company, New York, 1925
Findlay, A., Practical Physical Chemistry. Longmans, Green
and Company, New York. Fourth Edition, 1923
Getman, F. H. and F. Daniels, Outlines of Theoretical
Chemistry.
John Wiley and Sofas. New York. Fifth
Edition 1931
G i b s o n , R. E . , Special Report, Geophysical Laboratory,
Washington, 1900
Gibson, R. E., The System, Sodium Sulphate-Water• I. The
Densities and Specific Volumes of aqueous solutions of
Sodium Sulphate between 25 and 40°, and the fictive
volumes of Sodium Sulphate in solution,
J. Phys. Chem.
31:496 (1927)
Glass, H, M , , and W. M. M a d g i n , Viscosities of aqueous sol­
utions of electrolytes.
Part I.
Sodium Sulphate over
the Temperature range 25-40° 0, J. Chem. Soe., London
(1934) , 1124.
Hartshorne, N. H., An apparatus for the viscosimetric deter­
mination of transition points, J. Chem. Soc. , London
125:2096 (1924)
Heydwe i l l e r , A., Electrical conductivity and density of
aqueous solutions of electrolytes, Zeit. anorg. allg.
chem. 116:42 (1921)
International Critical Tables of Numerical Data. McGraw Hill
& Co., New York for National Research Council; 1926-30
3:26.
Density of water.
International Critical Tables of Numerical Data.
McGra?>r Hill
& Co., N e w York for National Research Council, 1926-30
5:10
Coefficients of Viscosity of water
45
International Critical Tables of Numerical Data. McGraw Hill
& Co., N e w York for National Research Council, 1926-30
6:234
Conductivity of Q.02N KC1
International Critical Tables of Numerical Data.
McGraw Hill
& Co., N e w York for National Research Council, 1926-30
4:4
Surface Tension of Benzene
International Critical Tables of Numerical Data. McGraw Hill
& Co., N e w York for National Research Council, 1926-30
3:29,33 Densities of Benzene
International Critical Tables of Numerical Data. McGraw Hill
& Co., N e w York for National Research Council, 1926-30
3:81
Specific Gravity of Sodium Sulphate Solutions
International Critical Tables of Numerical Data.
McGraw Hill
& §o., N e w York for National Research Council, 1926-30
5:15 Viscosities of Sodium Sulphate Solutions.
International Critical Tables of Numerical Data. McGraw Hill
& Co., New York for National Research Council, 1926-30
6:231
Conductivities of Sodium Sulphate Solutions
International Critical Tables of Numerical Data.
McGraw Hill
& Co., N e w York for National Research Council, 1926-30
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