NOTES
2784 Viscosities of Protonated and Deuterated Water Solutions of Alkali Metal Chlorides by A. G. Ostroff, B. S. Snowden, Jr., and D. E. Woessner Field Research Laboratory of Mobil Research and Development Corporation, Dallas, Texas 768.21 (Received January 17,1969)
Comparison of the viscosities of the D20 and H20 electrolyte solutions' should provide insight into the effects of various ionic species on the structure of the solution. Since pure D2O and H20 are considered to have different structural characteristics, the introduction of the alkali metal ions should affect the structure of the two types of water differently. This structural difference is expected to be reflected in the viscosity measurements. The series of alkali metal ions is particularly appropriate for this study because it contains ions which have the same net charge but a wide range of charge-toradius ratio. A comparison of the H 2 0 and D2O viscosities of these ionic solutions should demonstrate the effect of these ions on an aqueous solution. The object of this work is the determination of relative viscosities of both protonated and deuterated water solutions of LiC1, XaC1, KC1, RbC1, and CsCl a t 25". Although some of these data are available in the literature, we remeasured them to confirm our experimental technique.
Experimental Section Equipment. Cannon-Fenske kinematic viscometers of different capillary diameters were used in these measurements because of the range of viscosities studied. These viscometers were cleaned initially and periodically with chromic acid cleaning solution, washed with distilled water, and dried with a current of filtered dry air.2 Flow times were measured using stop watches equipped with indicating counters that could be read directly to 0.1 of a second. Viscosities were measured in a thermostatically controlled water bath which was adjusted to control temperature to 25 f: 0.01". The temperature of the bath was adjusted and monitored with a National Bureau of Standards calibrated thermometer. A Mettler Type H15 analytical balance was used in measuring the solution densities and in weighing the solvent and solute used in making the solution. Materials and Solutions. Lithium, sodium, and potassium chloride solutions were made using Baker's Analyzed grade chemicals. Rubidium and cesium chloride solutions were prepared using pure grade reagents abtained from E. H. Sargent Go. Distilled water was used in the H2O solutions and >99.5% deuterium oxide in the D 2 0 solutions. Solutions were made on a weight basis by weighing both solvent and solute. The dilute solutions of RbCl The Journal of Physical Chemistry
and CsCl were prepared by diluting on a weight basis solutions stronger than 3 m. Procedure. Solutions were loaded into the viscometer and placed in the bath and an hour was allowed for equilibration a t the bath temperature of 25" The solutions for density measurements were also placed in this bath. A minimum of five flow-time readings was taken for each solution. Solvent flow times were measured in all viscometers. The reported density values represent an average of at least three readings. A specific timer was used with a particular viscometer. Densities were measured at 25" using a plummet and an analytical balance. These densities were used in calculating relative viscosities.
Results and Discussion The measured relative viscosities and densities of the alkali metal chlorides in both protonated and deuterated
Y 1.000
0.800
XCI i n D20 RbCl I n HiO RbCl In DIQ (IC1 In HiO C i C l i n Q20
Q.??9 -1.W 21.469
---
71.173 14.027
1.001
-1.796
1.000
-2.636 31.416 57.968 -2.726 41.901 .138.79 -3.900 40.414 99.42'4
1.001
I.CDO
0.02
26.819
0.04
1.9 2.5 1.6 2.5
3.0
0.06
0. os
1
Figure 1. Relative viscosities of alkali metal chlorides vs. mole fraction.
water solutions are listed in Table I. The values €or LiCl in H 2 0 are in good agreement with those reported
in ICT3 as well as those reported by J a ~ o p e t t i . ~Both (1) D. E. Woessner, B. S. Snowden, Jr., and A. G. Ostroff, J . Chem. Phgs., 49, 371 (1968). (2) R. C. Hardy and R. L. Cottington, J . Res. Nat. Bur. Stand., A , 42, 673 (1949). (3) E. W.Washburn, Ed., "International Critical Tables," Vol. V, MoGraw-Hill Book Co., Inc., New York, N. Y.,1929, p 12. (4) M. Jaoopetti, Oazz. Chim. Ital., 72, 261 (1942).
2785
NOTES Table I : Measured Viscosities and Densities of Alkali Metal Chlorides Relative viscosity
Mole fraction
Density, g/ml
Mole fraction
1.144: 1.237 1.342 1.490 1.675 1.829 1.905 2.013 2.063
1.0198 1.0327 1.0465 1.0631 1.0801 1.0941 1.0995 1.1071 1.1117
LiCl in DaO 1.120 1.212 1.295 1.480 1.659 1.878 2.107 2,427
0.0151 0.0257 0.0346 0.0517 0.0669 0.0829 0.0967 0.1117
1.1233 1.1360 1.1449 1.1650 1.1787 1.1983 1.2124 1.2288
NaCl in HzO 1.098 1.222 1.381 1.587 1.861
0.0181 0.0355 0.0545 0.0729 0.0917
1.0371 1.0754 1.1131 1.1495 1.1844
NaCl in DzO 0.00698 0.0142 0.0212 0.0280 0.0348 0.0414 0.0480 0.0521 0.0593 0.0672 0.0750 0.0826
1.028 1.063 1.106 1.140 1.191 1.231 1.288 1.313 1.391 1.473 1.571 1.646
1.1192 1.1347 1.1494 1.1630 1.1767 1.1886 1.2014 1.2097 1.2246 1.2394 1.2533 1.2663
KCl in HzO 0.0089 0.0175 0.0264 0.0348 0.0431 0.0513 0.0593 0.0671
0.997 0.998 0,999 1.007 1.011 1.027 1.037 1.051
Density, g/ml
RbCl in Ha0
LiCl in HzO 0,0169 0.0268 0.0375 0.0511 0.0649 0.0782 0.0819 0.0895 0.0919
Relative viscosity
1.0197 1.0414 1.0624 1.0820 1.1003 1.1184 1.1357 1.1526
0.0078 0.0148 0.0199 0.0244 0.0255 0.0326 0.0429 0.0513 0.0588 0.0675 0.0754 0.0822
0.986 0.982 0.976 0.970 0.969 0.969 0.973 0.978 0.984 0.997 1.009 1.027
1.0344 1.0676 1,0910 1.1115 1.1171 1.1487 1.1937 1.2293 1.2604 1.2947 1.3264 1.3528
RbCl in DzO 0.0090 0.0178 0.0265 0.0350 0.0437 0.0516 0.0596 0.0682 0.0746 0.0803
0.980 0.961 0.950 0.944 0.942 0.939 0.942 0.947 0.952 0.962
1.1454 1.1831 1.2224 1.2599 1.2962 1.3285 1.3606 1.3935 1.4172 1.4382
CsCl in HzO 0.0089 0.0177 0.0263 0.0351 0.0431 0.0515 0.0593 0.0677 0.0828
0.983 0.966 0.953 0.951 0.952 0.955 0.957 0.966 0.984
1.0600 1.1199 1.1769 1.2332 1.2827 1.3329 1.3803 1.4265 1.5104
CsCl in DzO 0.0072 0.0143 0.0230 0.0315 0.0397 0.0450 0.0514 0.0597 0.0678 0.0831
0.978 0.957 0.938 0.928 0.921 0.913 0.917 0.914 0.917 0.934
1.1543 1.2013 1.2575 1.3106 1.3587 1.3912 1.4277 1.4756 1.5194 1.6007
NaCl and KC1 values in HzO correspond to those in ICT.a Values for CsCl in HzOare in general agreement with those reported by Lyons and Riley6 at the low and high concentrations; however, the values reported in Table I are slightly higher in the 0.0375-0.0650 mole fraction range. A four-parameter least-squares fit was made of the relative viscosity data, and parameters were determined for calculating relative viscosities of the alkali metal chlorides. The general equation for this calculation is
where C1, Cz, Ca, and Cd are coefficients given in Figure 1 and x is the mole fraction of solute. This equation allows the calculation of the relative viscosities at 25”. Standard deviations (u) for these curve-fitting equations are given in Figure 1. An indication of the goodness of eq 1 is seen from the fact that the C1values are very close t o unity, as is required by the definition of qr. Smoothed viscosity data for KC1, RbC1, and CsCl in both HzO and DzO are shown in Figure 1. Each of these salts decreases the relative viscosity. This effect increases with increasing cation radius. I n the alkali metal ions, the largest increase in viscosity with concentration is shown by LiCl and the next largest with NaC1. Figure 1 also illustrates that the decrease in the relative viscosity is greater in DzOsolutions than in HzOsolutions. It is known that the viscosity, temperature of maximum density, and heat capacity of liquid DzO are higher than for liquid HzO.e This has been interpreted as indicating that liquid DzO is more structurally ordered than liquid HzO because the degree of hydrogen bonding is greater’ in the former than in the latter. The relative viscosity measurements of both the small (Li+ and Na+) and large (K+, Cs+, and Rb+) cations are consistent with the hypothesis that DzO has more structural order than HzO. The viscosity results appear to substantiate the hypothesis8 that the structural order in these aqueous solutions decreases with decreasing charge-to-size ratio.
Acknowledgments. The authors wish to thank Jack T. Wall for his contribution in measuring the viscosities, J. S. Grisham, Jr., for his contribution to the computer programming, and to Mobil Research and Development Corporation for permission to publish this work.
KCI in DzO 0.0090 0.0178 0.0264 0.0350 0.0433 0.0516 0.0596 0.0676
0.986 0.984 0.978 0.981 0.981 0.988 0.995 1.005
1.1255 1.1465 1.1662 1.1838 1.2022 1.2166 1.2354 1.2496
(5) P. A. Lyons and J. F. Riley, J. Amer. Chem. Soc., 7 6 , 6216 (1954). (6) I. Kirshenbaum, “Physical Properties and Analysis of Heavy Water,” National Nuclear Energy Series, Manhattan Project Technical Section, Division 111, IVa, McGraw-Hill Book Co., Inc., New York, N. Y.,1951. (7) L. J. Kavanau, “Water and Solute-Water Interactions,” HoldenDay, San Francisco, Calif., 1964. (8) D. E. Woessner, B. S. Snowden, Jr., and A. G. Ostroff, J. Chem. Phus., 50, 4714 (1969). Volume 73, Number 8 August 1969
