Dissolution of Gases in Liquids. 45 



Cumulative evidence which may be a very strong argument 

 in favour of experimental facts may be a very weak argument 

 when applied, as it is by the dissociationists, to a theory, so 

 long as the theory is by no means essential for the interpreta- 

 tion of facts, and is, moreover, opposed to many of our scientific 

 beliefs and experiences. For even if van der Waals's admission 

 of the existence of a specific attraction between the dissolved 

 substance or ions and the solvent — which in my opinion 

 " opens half the turnpike gates " to the hydrate theory — 

 obviates any objections on the score of heat evolved, we still 

 have left the obstacles of the origin of the " enormous elec- 

 trical charges " on the ions, how atoms with opposite charges 

 can remain in a state of communism, and why, when oppo- 

 sitely charged, they do not stick to each other more firmly 

 than when uncharged : all of which objections Dr. Walker 

 does not attempt to remove. 



But, more potent than any such objections, there is a simple 

 experimental fact which the supporters of the dissociation 

 theory have hitherto found it convenient to ignore, namely, 

 that when sulphuric acid, or any similar substance, is mixed 

 with a large excess of water, instead of splitting it into ions 

 and forming a solution containing more acting units than the 

 acid -h water separately, the solution contains less acting- 

 units, the number of acting units being measured by the 

 depression produced by the solution on some independent 

 solvent, measured, that is, by the very means on which the 

 dissociationists rely for proving dissociation (Ber. d. deutsch, 

 chem. Gesell. xxiv. p. 3317, and Chem. News, lxiii. p. 290). 



Dr. Walker concludes his attack on me by attempting a 

 supercilious dismissal of my calculations of the freezing- 

 points of sulphuric-acid solutions. His objections are two- 

 fold : (1) that they involve a " thorough confusion of heat 

 with temperature " — an objection for which Dr. Walker may, 

 perhaps, be excused, as he drew his conclusions from an abstract 

 only of my paper, but which he will find to be groundless 

 if he refers to the full paper, which is at present in the hands 

 of the Chemical Society ; and (2) that they are based on 

 Person's so-called absolute zero while my own subsequent 

 work has proved Person's views to be utterly untenable. For 

 this latter most unfortunate objection Dr. Walker can have 

 no excuse : it is true that my work proved that Person's 

 zero, or rather temperature of no crystallization, was not a 

 constant for all bodies, as Person had imagined it to be, but 

 the values for it which I obtained in the case of those two 

 solvents, water and the monohydrate of sulphuric acid, where 

 my calculated freezing-points agreed very closely indeed with 



