On the Physical Properties of Aqueous Solutions. 47 



Simple Solutions. 



In order to test the applicability of the above expression 

 I have determined the ionization-constants for the density, 

 thermal expansion, viscosity, surface-tension, and refractive 

 index of solutions of Sodium and Potassium Chlorides, by the 

 aid of observations made by Bender*, Bruckner f, and Bother J. 

 I selected these observations as a first instalment not because 

 of their precision (for in one or two cases more exact obser- 

 vations are available) , but because these observers, in all cases 

 but one, determined the values of the above properties for 

 mixtures of solutions as well as for simple solutions. I 

 selected the above chlorides partly because I thought it well 

 to begin with salts of simple molecular structure, but largely 

 also because, for the purpose of calculating the conductivity 

 of mixtures of them (as described in my paper on this sub- 

 ject §), I had already obtained interpolation formulae and 

 curves which, judged by the results of that paper, gave with 

 considerable accuracy the ionization-coefficients of the simple 

 solutions of these salts in terms of their molecular concentra- 

 tion. To save space I may tabulate here the values of the 

 ionization-coenicients used in the calculations for simple 

 solutions. They are as follows : — 



Sodium Chloride. 



Potassium Chloride. 



Grm.-mols. 

 per litre. 



Ionization- 



coefficient at 



18° C. 



Grm.-mols. 

 per litre. 



Ionization- 

 coefficient at 



18° O. 



•25 

 •5 



•8928 

 10 

 ]5 



1-8353 

 2-0 

 2-5 



28373 

 30 

 3-9375 



•792 



•736 



•6866 



•676 



•633 



•601 



•5866 



•5504 



•5255 



•514 



•4516 



•1875 



•3402 



•375 



•5 



•6856 



•75 



1-0 



1-0467 



1-4292 



1-5 



20 



2-185 



2-5 



2-986 



30 



•8267 



•811 



796 



•788 



•769 



•768 



•756 



•755 



•731 



•731 



•712 



•7048 



•695 



•681 



•680 



* Wied. Ann, vol. xxii. (1884) p. 184, and vol. xxxix. (1890) p. 89. 

 t Ibid. vol. xlii. (1891) p. 293. % Ibid. vol. xxi. (1884) p. 576. 



$ Phil. Mag. [5] xli. p. 276 (1896) ; and Trans. N.S. Inst. Sci. ix. 

 (1896) p. 101. 



