VIL. ON SOLUBILITY. 851 
ception of hydration in aqueous solution so as to embrace the idea of 
dissociation by suggesting that hydration may go so far as to separate the 
solute into two or more hydrated ‘ ions.’ 
This view of the changes taking place on dissolution was criticised by 
Dreaper,?*® who maintained that hydration does not completely sever the 
primary bond between the elements. 
Jones and Basset *** considered the fact of the amount of water of 
erystallisation being a function of the temperature to be a strong argu- 
ment in favour of the view that salts dissolve by virtue of their power to 
combine with the solvent.* 
When criticising Roozeboom’s explanation of some peculiar solubility 
graphst on the assumption of hydrate formation, Van Laar* expressed 
the opinion that hydration must be attributed mainly to the ‘ ions ’ if the 
peculiarities referred to are to be explained adequately. 
Schiller ?°* also contributed a mathematical paper dealing with the 
reciprocal behaviour of solvent and solute. 
1906 Winkler **? continued his work on the absorption of gases in 
" water at different temperatures, and established the relationship 
which he had already discovered between the absorption coefficient of a 
gas, its molecular weight and the internal friction of the water. Rex ?°* 
studied the solubility of halogen derivatives of hydrocarbons and con- 
cluded that the dissolution of these substances in water is a process of 
absorption just as in the case of the absorption of a gas. This author 
also found the value k in Winkler’s formula? increases with tempera- 
ture, and when calculated for each of a series of derivatives increases 
regularly with the atomic weight. 
An attempt was made by Walden *** to find some general relationship 
between solvent and solute. “He examined the solubility of a number of 
tetralkylammonium halides in various organic solvents, § but his results 
did not seem capable of general interpretation in terms of any particular 
theory. The observation that saturated solutions of tetramethyl- 
ammonium iodide in various solvents are all dissociated to the same 
extent—have equivalent molecular conductivity—appeared to be of some 
significance. 
Smirnoff 28* studied the separation of liquids into layers—salting out 
phenomena—and concluded that the added salt becomes associated with 
the solvent. 
The observation made by Fischer *** that hydrogen chloride at first 
raises, and then with increasing concentration lowers the solubility of 
B-napthalene sodium sulphonate is in agreement with the results ob- 
tained by Noyes. Fischer attributed the subsequent lowering of solu- 
bility to the withdrawal of water from solvent action by the hydrogen 
chloride, or to some considerable change in the solvent medium. 
Longinescu ** considered dissolution to be a purely physical pheno- 
menon. He found a criterion for the solubility of organic compounds 
in water in the magnitude of the ratio of the absolute boiling-point to the 
molecular weight. If this ratio is greater than 5 for any substance, then 
* Arguments similar to these had been published previously (1904) by Jones and 
Getmann.? + Zeitschr. physikal. Chem., 58, 449. 
{ Vide Part [..190. § Compare Sections ILI, B. and IV. B. 
312 
