.
RELATIVE VISCOSITIES O F YON-AQUEOUS SOLUTIONS
387
opposite sign; but this is to be expected, as in liquid salts the chief attractive force is electrostatic, and as the size of the ion increases, the attractive force decreases. Salts of higher molecular weight have, frequently, lower boiling points than similar salts of lower molecular weights. The value of nR in the table seems to be approximately constant for like molecules. For normal liquids with large polyatomic molecules this number is about 11. For certain other substances with monatomic molecules,-such as argon, neon, mercury, and zinc,-this number is about 5. For fused uniunivalent salts, n is approximately 9. For associated liquids in which the vapors are not polymerized, such as the alcohols of lower molecular weight, n is larger, being 14 or greater. REFERENCES (1) BINGHAM, E.C.: J. Am. Chem. SOC.28, 723 (1906). (2) DEFORCRAND, R . : Compt. rend. 166, 1493 (1913). (3) EQLOFF, G.,SHERMAN, J., AND DULL,R . B . : J . Phys. Chem. 44,730 (1940). (4) HILDEBRAND, J. H . : J. Am. Chem. SOC.37, 970 (1915); 40,45 (1918). (5) HUFFINGTON, J. D . : Phil. Mag. [7] 19, 836 (1935). (6) KISTYAKOVSKII, V.A,: J. Russ. Phys. Chem. SOC.6.9, 256 (1921). (7) MORTIMER, F . 6.: J. Am. Chem. SOC.44, 1429 (1922). (8)NERNBT, W.: Nachr. kgl. Ges. Wiss. Gottingen (1906). (9) TROUTON, F . : Phil. Mag. 151 18,54 (1884).
STUDIES OF RELATIVE VISCOSITY OF NON-AQUEOUS SOLUTIONS' H . T . BRISCOE
AND
WILMER
T. RINEHART
Department of Chemistry, Indiana University, Bloomington, Indiana Received November 15, 1941
This investigation has to do with the effect of temperature upon the relative viscosity, 70, of non-aqueous solvents containing electrolytes and non-electrolytes. Consideration has also been given to the Griineisen effect in solutions containing an inorganic salt, namely, potassium iodide dissolved in a non-aqueous solvent. EXPERIMENTAL
Exactly 5 ml. of liquid was measured into Ostwald-type viscometers at 25'C. As a check, two viscometers used for each determination always contained a solution of the same concentration. The liquid inside the viscometers was protected from the atmosphere by means of soda lime tubes. The viscometers were suspended in a constant-temperature bath by means of rigid glass supports Presented by Wilmer T. Rinehart to the Faculty of the Graduate School of Indiana University in partial fulfillment of the requirements for the degree of Doctor of Philosophy, October, 1940.
388
H. T. BRISCOE .4ND WILMER T. RISEHART
in such a way that they were aligned in exactly the same manner for each run. The temperature of the bath was maintained to within f 0.05°C. An interval of 15 to 30 min. was allowed for the liquid in the viscometers to attain the temperature of the bath. The liquid was then allowed to flow through the viscometers once before the rate of flow was timed with a stop watch reading to 0.1 sec. The average of five readings was taken for each temperature and viscometer, and the time was approximated to 0.01 sec. After each run the viscometers were flushed with cleaning solution and rinsed, first with distilled nater and then with alcohol. Dry filtered air was drawn through the viscometers to dry them. All liquids used in the experiments and in the cleaning procew were filtered through sintered-glass filters, in order to minimize difficulties due to dirt and lint. Calibrated pycnometers of 10-ml. capacity wcre nsed in density determinations. The density of each solution is defined as the weight in grams of 1 ml. of the solution relative to the weight of 1 ml. of pure mater a t 4°C. The roncentration, C, is given in gram-moles per liter. DISCUSSION OF RESULTS
The relative viscosities of aqueous solutions of electrolytes increase with increasing temperature no matter whether the addition of the electrolyte causes an increase or a decrease in the viscosity. The irlative viscosities of aqueous solutions of non-electrolytes always decrease with increasing temperatui e. Tables 1 and 2 show that the relative viscosities of solutions of non-elevtrolytes in benzene decrease with increasing temperature and, therefore, that these solutions resemble in this reapect aqueous solutions of non-electrolytes. Potassium iodide is relativelv soluble in methanol. I t is highly ionized, as is shown by the high conductivity of the solution. The addition of potassium iodide to methanol increases the viscosity. Tables 3 and 4 show that the relative viscosity of solutions of naphthalene and of potassium iodide in methanol decreases nith increasing temperature. These solutions, therefore, in this respect resemble aqueous solutions of non-electrolytes, although one solute is an electrolyte and the other a non-electrolyte. Potassium iodide is quite soluble in glycerol and causes the viscosity to be lowered. Table 5 shows that the relative viscosity of solutions of potassium iodide in glycerol increases with increasing temperature ovei the whole concentration range; in this respect, therefore, this solution resembles aqueous solutions of electrolytes. The potassium iodide-glycerol solution offers an interesting contrast to the potassium iodidemethanol solution in this respect, and also because the viscosity of glyrerol is lowered by the addition of potassium iodide. Figure 1 shows the variation of 70 with temperature for solutions of approximately the same concentration. There is a great difference in the relative viscosity of pot'zssium iodide-glycerol and potassium iodide-methanol solutions. Naphthalene produced practically the same effect in methanol as in benzene. Figure 2 shows that plotting concentration against 70 for potassium iodide-
389
RELATIVE VISCOSITIES OF NON-AQUEOUS SOLUTIONS
TABLE 1 Naphthalene i n benzene d
T 'C
!
C
C
.
60
0.8754 0.8699 0,8594 0.8486 0.8379
0.1021 0.1014 0.1002 0.0990 0.0977
25 30 40 50 60
0.8832 0.8780 0.8675 0.8569 0,8460
25 30 40
0,8956 0.8904 0.8603 0.8700 0.8596
25
30 40 50
50 Bo
~1
0.2427 0.2412 0.2383 0.2354 0.2324
1.0355 1,0345 1 ,0327 1.0315 1.03%
0,4984 0.4954 0.4895 0,4835 0,4775
0.6025 0,7978 0.7885 0.7792 0.7698
1,1218 1.1186 1.1133 1,1095 1.1061
1.1271 1.1205 1.1078 1,0949 1.0818
1.4733 1.4650 1.4486 1.4320 1.4155
1.2394 1.2318 1.2197 1.2113 1.2055
C
no
0 2477 0 2462 0 2433 0 2403 0 2372
1.0512 1 ,0498 1.0475 1.0458 1.0448
0 7034 0 7890 0 7801 0 7709 0 7617
1,1782 1.1724 1.1634 1,1577 1.1532
1 4543 1 4463 14306 1 4149 1 3084
1,3625 1.3498 1.3288 1,3135 1.3025
1 0150 1 0147 1 0140 1 0134
'1
0 0 0 0
8782 8728 8623 8516
TABLE 2 Diphenvl i n benzene T
d
'C.
0.8757 0.8703 0.8599 0.8490 0.8383
0 0976
0.8853 0.8802 0.8696 0.8591 0.8486
04990 0 4961 0.4902 0.4843 0,4783
50
0.9004 0.8954 0.8853 0,8750
80
0.8649
1.1259 1.1197 1.1071 1,0942 10816
25 30 40 50
60 25 30 40 50
60 25
30 40
0 8740 0 8635
1 0192
1
'~'
0 8923 0 8873
1
0 8669 0 6566
2672 2588
'
0 9082 09032
1.2265
1,
0.8733
11064 1 1037 0951 0924
1
~
glycerol solutions does not give a straight line, as previously reported (1). I t is again apparent that the curves for naphthalene-methanol and for naphthalenebenzene solutions practically coincide.
390
H. T. BRISCOE AND WILMER T. RINEHART TABLE 3 Xavhthalene in methanol T
d
C
0.7899 0.7854 0.7806 0.7758 0.7711 0,7663
0.0993 0.0987 0.0981 0.0975 0.0969 0.0963
0.7983 0.7936 0.7889 0.7842 0.7796 0,7747
0.3483 0.3462 0.3442 0.3421 0.3401 0.3380
C
10
0.1953 0.1942 0.1931 0.1919 0.1907 0.1895
1.0286 1 .0277 1 ,0268 1.0262 1,0258 1.0255
0.4984 0.4956 0.4927 0.4897 0.4868 0.4839
1.0732 1.0704 1.0679 1.0663 1.0651 1.0641
'C.
25 30 35
40 45 50
25 30 35 40 45 r)
1.0147 1.0140 1.0133 1.0130 1.0127 1.0125
0.7932 0.7884 0.7839 0.7790 0.7744 0 7695
TABLE 4 Potassium iodide in methanol T
d
C
C
0.7942 0.7895 0.7849 0.7801 0.7755 0.7705
0.0506 0,0503
0,0985 0.0979 0.0973
0.0497 0.0494 0.0491
0.0968 0.0962 0.0956
1.0610 1.0596 1.0586 1.0579 1.0574 1 ,0570
0.8155 0,8109 0.8061 0.8014 0.7969 0.7922
0.1090 0.1979 0.1967 0.1956 0.1945 0,1933
0.3480 0.3460 0.3441 0.3421 0.3401 0.3381
1.1828 1.1781 1.1750 1.1726 1.1710 1.1699
0.8585 0.8539 0.8492 0.8446 0.8397 0.8349
0.5037 0.5010 0.4982 0.4955 0.4926 0.4898
0.6057 0.6023 0.5992 0.5958 0.5925 0.5893
1.3013 1.2945 1 ,2895 1.2858 1,2830 1.2803
0.8933 0,8885 0.8837 0.8791 0.8746 0.8695
0.7523 0.7482 0,7442 0.7403 0.7365 0.7322
T.
25 30 35 40 45 50
25 30 35 40 45 50
25 30 35 40 45 50
25 30 35 40 45 50
0.0501
TABLE 5 Potassium iodide in glycerol T
d
C
70
1.2784 1.2750 1.2688 1.2622 1.2558 1.2492
0.1970 0.1965 0.1955 0.1946 0.1936 0.1926
0.98% 0.9837 0.9850 0.9868 0.9888 0.9914
1.2957 1.2925
0.3647 0.3638
1.2729 1.2665
0.3601 0.3583 0.3565
0.9586 0.9603 0.9648 0.9700 0.9747 0.9800
C
-~
'C.
25 30 40 50
60 70 25
30 40 50
60 70 25
30 40 50
60 70 25 30 40 50
60 70 25 30 40 50
60 70 25 30 40 50
60 70
1.2690 1.2657 1.2594 1.2530 1.2465 1.2400
0.1045 0.1042 0.1037 0.1031 0.1026 0.1021
0.9934 0.9936 0,9944 0.9961 0,9964 0.9972
1.2859 1.2824 1.2760 1.2696 1.2631 1.2567
0.2675 0.2667 0.2651 0.2641 0.2627 0.2614
0.9728 0.9739 0.9767 0.9796 0.9830 0.9865
1.3086 1.3052 1.2992 1.2927 1.2860 1.2796
0.4926 0.4913 0.4890 0.4866 0.4841 0.4814
0.9721
1.3392 1.3358 1.3292 1.3225 1.3161 1.3093
0.7899 0.7879 0,7840 0.7800 0.7762 0,7722
1.3908 1.3872 1.3806 1.3740 1.3670 1.3603
1.2976 1.2943 1.2881 1.2819 1.2754 1.2691
1.4360 1 ,4323 1.4254 1.4184 1.4117 1.4048
1,7438 1 ,7393 1.7309 1.7224 1.7143 1 ,7058
1 1
0.3620
1.2968
0.6635 0.6603 0.6570 0.6537 0.6504
0.9168 0.9211 0.9304 0.9404 0.9505 0.9616
0.9013 0.9065 0.9176 0.9293 0.9418 0.9550
1.3586 1.3549 1.3484 1.3418 1.3350 1.3283
0.9812 0.9784 0.9737 0.9690 0.9641 0.9592
0.8779 0.8839 0.8985 0.9119 0.9293 0.9445
0.8425 0.8510 0.8688 0.8873 0.9085 0.9265
1.4087 1 ,4052 1.3984 1.3915 1.3847 1.3779
1.4740 1.4703 1.4632 1.4560 1.4488 1.4417
0.8262 0.8364
2,1770 2.1716 2.1620 2.1516 2.1412 2.1309
0.7876 0.7978 0.8224 0.8464 0.8725 0.9oOo
0.6653
0.8554
0.8758 0.8970 0.9195
TABLE 6 PhvsicaE constants of oraanic chemicals used
1
I
SOLVENT
DENSITY
_At -ZS'C.~ - At_30'C._ _ At_40T. _
1
At S O T .
.
At W'C.
I *e.
xxmrna POINT
SOLrnE
Diphenyl. , . . . . . . . . . . . . . . . . . . . Naphthalene. . , . . . . . . . . . , . . . . .
1
. .. ... .... . ... . .. . . ... . ... .... .. ... .... ... .. , . . . . . . ... 391
"C. 69 80.25
392
OC.
1.02
1.10
1.18
RELATIVE VISCOSITY k t . F ~ ~ . fVariation l. of
70
with temperature for solutions of approximately the earn8
concentration.
MOLAR CONCENTRATION FIG.2. Plot of concentration against
70 for
solutions at 25OC.
Griineisen (2) discovered for several aqueous salt solutions that the expression ( T ~ -1)/C decreased with increasing concentration until a minimum value was
reached and then increased. This was true no matter whether the salt increased
RELATIVE VISCOSITIES O F XOX-AQUEOUS SOLUTIONS
MOLAR
393
CONCENTRATION
FIG.3. Solutions of potassium iodide in methanol
MOLAR CONCENTRATION FIG.4. Solutions of potassium iodide in glycerol
or decreased the viscosity. Xon-electrolytes do not exhibit this property when dissolved in water. Jones and Fornwalt (3) have recently studied several organic solvents in which inorganic salts were dissolved and found that they exhibited
394
H. T. BRISCOE AND WILMER T. RINEHAFLT
the Griineisen effect to a marked extent. Not to our knowledge has anyone reported a solution of a non-aqueous solvent and an inorganic salt for which the expression ( 1 0 - 1)/C increases after dropping to a minimum. Figures 3 and 4 present an interesting contrast in the Griineisen effect a t different temperatures. When (70- l)/C is plotted against molar concentration for solutions of potassium iodide in methanol, the Griineisen effect is more pronounced at 50°C. than a t 25°C. and there is no concentration a t which the curve rises. The opposite is true for solutions of potassium iodide in glycerol; for these solutions the Griineisen effect is greater a t 25°C. than a t 70"C., and the curve does rise after a minimum has been reached a t about C = 0.7. SUMMARY
1. The variation of relative viscosity with temperature has been studied for solutions of naphthalene in benzene and in methanol, of diphenyl in benzene, and of potassium iodide in methanol and in glycerol. It was found that the relative viscosity decreaaes with increasing temperature for all solutions studied except that of potassium iodide in glycerol. The viscosity of the solvent was lowered by the addition of a solute only in the case of the solution of potassium iodide in glycerol. 2. Only the solutions containing potassium iodide exhibited the Gruneisen effect. For the solutions of potassium iodide in glycerol, (qo-l)/C was found first to decrease and then to increase, after reaching a minimum a t about C = 0.7. It is interesting to note that the behavior of the potassium iodide-methanol solution resembles that of a water-electrolyte solution with respect to the Griineisen effect, but acts as a typical water-non-electrolyte solution with respect to the effect of temperature variation on the relative viscosity. The potassium iodide-glycerol solutions behaved in all respects as typical water-electrolyte solutions. REFERENCES
(1) GETMAN,F. H.: J. Am. Chem. SOC.30, 1077 (1908). (2) GRUNEISEN,E.: Wiss. Abhandl. physik.-tech. Reichsanstalt 4, 239 (1905). (3) JONES, G., AND F O B ~ W A LH.: T , J. Am. Chem. SOC. 67, 2041 (1935).
