232 
Proceedings of the Royal Society 
Similarly, tlie double salts, such as the chloride of potassium and 
platinum, may be represented thus — 
The same principle may be applied to water of crystallisation, &c. 
If this spreading out of chemical affinity be admitted, it may be 
extended to include solutions and other weak combinations; thus, a 
solution of salt in water may be represented thus — 
and it is manifest any number of molecules of water may be added; 
each one, of course, weakening the bonds of union. That some 
such action as this takes place may be inferred from the behaviour 
of magnesium chloride in water. The chloride cannot be recovered 
by evaporation, because, from the strong affinity of the magnesium 
for oxygen, and of chlorine for hydrogen, double decomposition takes 
place, and hydrochloric acid is liberated, while magnesium oxide 
remains. The same principle is illustrated by the phenomena of 
electrolysis, with the varying resistances of solutions of different 
strength, causing the concentration or diffusion of the chemical 
affinity. 
Alloys, solution, and occlusion of gases may all be included 
under the law of the spreading of chemical affinity. 
There are also some physical facts on which it may throw some 
light. Thus, the fact that gases in their behaviour under pressure 
indicate first an attractive, and then a repellant action among 
their molecules, may be explained by the influences of the com- 
ponent parts of each molecule acting on its neighbours, and 
producing attraction ; while the repellant action may be accounted 
for by assuming a motion of revolution round an axis when the 
