1910. | with the State of Aggregation of Matter. 105 
tensiong. In the latter, the solubility of crystalline substances was generally 
less than that of water; in the former it was generally greater. These 
results are especially marked in the case of caffeine. 
The solution capacities of the salts do not all follow in absolutely the 
same order in the case of all salts. The rate of diffusion and the surface 
tension at the junction of the phases could not be directly measured, and in 
some instances the former exerted a greater effect than the latter. Hence, 
in some cases, sodium formate has a greater solution capacity than sodium 
chloride, in others less. If, however, the salts be arranged in series, viz., the 
inorganic salts, with solutions of low viscosity, the organic salts, with 
solutions of high viscosity, with sodium formate forming an intermediate 
class by itself, it will be invariably found that the dissolving capacity of salt 
solutions of the same series bears a direct relationship to the surface tension. 
It was also thought possible that the state of hydration of the salts in 
solution might exert some influence, in that, owing to combination of salt 
with water, less water in a normal solution would be available to act as 
solvent. W. Bilz* and H.C. Jonest have suggested that the abnormally great 
depression of freezing point of water produced by solutions of salts was due 
to the forrhation of hydrates in solution. The molecular depression of the 
freezing point of various salts was therefore investigated, and it was found 
that that of the organic salts was, as a rule, greater than that of the inorganic 
salts. Sodium formate, however, depressed the freezing point of water to 
about the same extent as did sodium chloride. 
If the state of hydration played the chief rd/e in determining the solubility 
of a crystalline substance in a salt solution, sodium formate solution should 
have had about the same solution capacity as sodium bromide and sodium 
nitrate. The solution capacity was invariably less, and less also in some 
cases than that of sodium chloride solution, which has a higher surface 
tension. It does not appear, therefore, as if the state of hydration plays 
a very direct part in determining the solution capacity of a salt solution, 
although it may play an indirect part, in that a highly hydrated salt may 
form a more viscous solution than one less hydrated in solution (compare in 
tables, viscosities and freezing points of sodium chloride and sodium iodide, 
sodium chloride and lithium chloride, sodium benzoate and sodium salicylate). 
In the case of leucine and phenylalanine, both of which contain a 
carboxyl group, solutions of the salts of polyvalent metals possessed a greater 
solution capacity than those of the monovalent metals, the chlorides of the 
triad metal cerium dissolving more of these substances than any other 
* ¢ Zeitsch. Physikal. Chem.,’ 1902, vol. 40, p. 485. 
Tt ‘Publications of the Carnegie Institute,’ 1907. 
