of Edinburgh, Session 1885-86. 
779 
comparatively small dose (0*04) in cats; with benzoylecgonin the 
convulsions are spinal in origin, and come on later. Local applica- 
tion of benzoylecgonin to the eye has no effect on the pupil, while 
cocain dilates it markedly. 
I have to express my thanks to Professor T. R Fraser for much 
valuable criticism and advice while carrying on the investigation. 
3. Laws of Solution. By William Durham. 
In my paper on “ Chemical Affinity and Solution,” read before 
the Royal Society of Edinburgh on 16th February last, I gave 
some general proofs of the correctness of my theory of solution, 
taken from Thomsen’s researches on thermo-chemistry, as given in 
Muir and Wilson’s book on that subject. In the present paper I 
propose to extend these proofs, and to show the laws of solution, so 
far at least as chlorides, bromides, and iodides are concerned. I 
have verified these laws in the case of many sulphates, and have no 
doubt they govern all cases of solution. My theory is simply this, 
“ Solution is due to the chemical affinities of the constituent atoms 
or elements of the body dissolved for the constituent atoms of the 
solvent.” For instance, the solubility of BaCl 2 in water is due 
mainly to the affinity of the Ba of the salt for the 0 of the water, 
and of the Cl of the salt for the H of the water, and the degree of 
solubility depends on the relation between these affinities. Now it 
can be shown, from Thomson’s researches, that the heats of solution 
in water of chlorides , bromides , and iodides vary directly — 
1st, As the affinity (as measured by heat of combination) of the 
positive element for 0 varies ; 
2nd, As the affinity (as measured by heat of combination) of the 
negative element for H varies ; 
and inversely — 
As the affinity (as measured by heat of combination) between the 
positive and negative elements of the salt varies. 
That is, the greater affinity the positive element has for O, and the 
greater affinity the negative element has for H, the greater is the 
