VII. ON SOLUBILITY. 853 
that complexes are formed was held to be frequently unnecessary as an 
explanation of solubility phenomena. 
In connection with the velocity of dissolution, Bruner and Tol- 
loczko *1* confirmed the Noyes-Whitney formula, not only for slightly 
soluble substances, but even for solutes such as sodium chloride. 
The ‘ ionic dissociation ’ theory of solution was strongly attacked by 
Armstrong,*** who advanced evidence and argument in favour of the 
view that union takes place between solvent and solute. It was insisted 
upon that the solvent must be regarded as playing an important part in 
conditioning dissolution, and that the molecular complexes which con- 
stitute solids and liquids become simplified. For example, water is con- 
sidered to be an equilibrium mixture represented by (H,O)n 2 nH,0, 
and the simplex molecular H,O, called hydrone, is regarded as being the 
active agent* effecting dissolution. 
Rothmund *** published a paper dealing with solubility influences and 
discussed the evidence he had obtained when using aqueous solutions of 
slightly soluble salts, and previous work relating to experiments with 
more soluble salts. The conclusions he came to were that the nature 
of this influence of non-electrolytes on the solubility of electrolytes de- 
pends upon the individual character of the substances in solution—upon 
some interaction between them, and not between solvent and solute. 
1909 It was demonstrated by Timmermans *** that the mutual solu- 
* bility of two non-miscible liquids depends upon the external 
pressure, and that it is possible to pass continuously from dilute to con- 
centrated solutions by varying the pressure. On the basis of this fact 
the author proposed to elaborate a theorem, applying to concentrated 
solutions the conceptions of Van der Waals. 
Hudson **° developed a theory of solution in which he supposed 
hydrated and anhydrous salt capable of existing together in solution. t+ 
Gillet *** also favoured an hydration theory of solution; he supposed 
water to be a mixture of dihydrol and hydrol—(H,O), =H,O0* +H,0- 
—and considered all aqueous solutions to be compounds of solute with 
either positive H,O*, or negative H,0-, hydrol. 
A paper dealing with complex mathematical equations respecting the 
representation of solubility influences, published by Rothmund,*°7 con- 
tained also observations on the diminution of solubility of a salt as caused 
by the presence of non-electrolytes. This author considered Philip’s 
method of calculating hydration values (R. 307) to be indefensible, and 
also adversely criticised the views expressed by Abeggt and by Hudson | 
(R. 360). Traube *4* maintained that quite irrespective of any question 
of quantitative correctness in certain cases, the electrolytic dissociation 
hypothesis is based upon a fundamental error inasmuch as no regard is 
paid to the ‘ intensity factor.’§ This factor he called the ‘ cohesion 
* Vide Armstrong on ‘ The Origin of Osmotic Effects,’ Proc, Roy. Soc., 78, 264. 
t+ Vide Section V., C. ii. 
t Zeitschr. f. elektrochem. (1901), £. 677. 
§ In connection with these and similar views, reference should be made to the 
per by Bose and Bose (Zeitschr. physikal. chem., 69, 58) dealing with the localisation 
of molecular forces and a discussion of the attractive constant a of Van der Waals’ 
equation. 
