652 SCIENCE PROGRESS 



of composite electrolytes generally — to be explained, if not by 

 the assumption that the solute is dissociated into ions ? The 

 expression " thirst" is used advisedly, as being far more appro- 

 priate than the term "osmotic pressure," as the thirst experienced, 

 for example, after eating salt junk is that engendered by the 

 intrusion of salt into the water in the cells of the organism. 

 The thirst originates in the salted water. 



In 1885 and 1886 I insisted that both constituents of the 

 composite electrolyte, water as well as salt, acted reciprocally ; 

 this view I have never departed from. The idea has constantly 

 been present in my mind that the act of dissolution involves 

 some form of conjunction — yet not hydration as commonly 

 understood. I made this quite clear in 1887 in the British 

 Association report on electrolysis, where the following state- 

 ment will be found : 



Nor do I conceive that it helps us to assume that a com- 

 pound of hydrogen chloride with water is formed : it does not 

 appear to me to be probable that an aggregate of the form 

 (HCl)j(OH 2 ) x would be more susceptible of electrolysis than the 

 component simple molecules and that these would be more 

 likely to suffer dissociation when associated than when free. 



My work has so often been referred to in conjunction with 

 that of Pickering on the determination of the composition of 

 hydrates in solutions that it is desirable to point out that the 

 questions considered by us were of a very different character. 

 I always believed in the existence of hydrates but I was in 

 search of something more — of a process, in fact, to account for 

 the reciprocal character of the effect which solute and solvent 

 exercised ; one which at the same time would make it possible 

 also to explain the effects produced by non-electrolytes. The 

 explanation suddenly flashed into being after the discussion on 

 ions in the Physical Section of the British Association in Brad- 

 ford in 1900, the last occasion on which we enjoyed Fitzgerald's 

 stimulating presence. 



Taking into account the effect produced on water by a 

 substance such as alcohol, for example (in lowering the freezing- 

 point, etc.), as the extent to which such a substance could be 

 supposed to exert a " dehydrating " action was very limited, it 

 appeared obvious that its action must be " mechanical " rather 

 than chemical ; consequently, that the real change must be in 



