On the Mutual Solubility of Salts in Water. 75 



cr and a 10 being the resistances at 0° and 10°. According to 

 my own results in 1888 we should have 





~r00876' 



and the value of <r would be increased from '95334 to about 

 •95360, which is rather greater than my value. The value 

 •000876 is given by Benoit for the mean coefficient between 

 0° and 10°. 



XII. On the Mutual Solubility of Salts in Water. 

 By J. E. Tkevor *. 



INTEREST in this problem has been again aroused by a 

 new investigation by Dr. W. W. J. Nicol t, in which is 

 presented a review of the older literature, together with new 

 solubility determinations and a series of interpolation formulae 

 to express the results. Inasmuch as no mention is made of 

 the recent investigations which have shed so much light 

 upon this hitherto dark subject, I take this opportunity to 

 call attention to the solidly grounded explanations which 

 characterize the more recent progress in the study of the 

 complicated phenomena which are here presented. 



That the addition of a salt to the saturated solution of 

 another sometimes increases, sometimes diminishes the solu- 

 bility of the latter, has been long known. The explanation w T as 

 first given in 1889 by Nernst |, in a simple application of 

 the famous Law of Mass Action § to the conditions of electro- 

 lytic dissociation shown by Arrhenius || to exist in aqueous 

 solutions of electrolytes, to which class of bodies the inorganic 

 salts belong. This theory, as is well known, indicates the 

 necessity for assuming the dissociation of a certain portion of 

 the dissolved electrolyte into its ions, and is intimately con- 

 nected with the van't HofT theory of osmotic pressure If, which 

 shows the entire analogy between the conditions of bodies in 

 gaseous form and in solution. The undissociated dissolved 

 molecules and the dissociated ions produce the same pressure 

 effects as the undissociated and dissociated molecules of a 

 gas. Direct application of the laws of gases explains the 



* Communicated bv the Author. 

 t Phil. Mag. 1891, xxxi. p. 369. 

 % Nernst, Zeitschrift fur phys. Chemie, iv. p. 372. 

 § Theory of Guldberg and Waage. 

 ,|,| Arrheniii^ Zeitschr. fur phys. Chem. i. p. 631. 

 11 Van't Hoff, Zeitschr. fur phys. Chem. i. p. 481. 



