648 SCIENCE PROGRESS 



following passage in his life by Koenigsberger (English trans- 

 lation, p. 340) : 



" Nernst has thrown himself zealously into the newest 

 applications of physical chemistry, as worked out by the Dutch- 

 man Van't Hoff and advocated with great vigour by Professor 

 Ostwald of Leipzig in his Journal. These theories have already 

 proved to be of great practical utility and have led to a multitude 

 of demonstrably correct conclusions, although they imply some 

 arbitrary assumptions which do not seem to me to be proven. 

 The chemists, however, make use of this hypothesis [of the 

 dissociation of a portion of the compound molecules of the 

 dissolved salts] in order to form a clear conception of the pro- 

 cesses' and they must be allowed to do this after their fashion, 

 since the whole extraordinary comprehensive system of organic 

 chemistry has developed in the most irrational manner, always 

 linked with sensory images, which could not possibly be legiti- 

 mate in the form in which they are represented. There is a 

 sound core in this whole movement, the application of thermo- 

 dynamics to chemistry, which is much purer in Planck's work. 

 But thermodynamic laws in their abstract form can only be 

 grasped by rigidly trained mathematicians and are accordingly 

 scarcely accessible to the people who want to do experiments 

 on solutions and their vapour tensions, freezing points, heats of 

 solution, etc." 



The fact which Helmholtz did not sufficiently appreciate was 

 that the men who were taking the liberties he deprecated were 

 not chemists, at least in feeling — that they were men who had 

 thrown chemistry to the winds and were proceeding on hypo- 

 thetical let-it-be-granted principles. The physico-chemical 

 school, in fact, has never been a school of chemists. 



The one chief "nasty, ugly little fact" which has spoilt the 

 dissociation hypothesis is the fact that the solvent has always 

 been neglected by the advocates of the speculation. To Kohl- 

 rausch it was simply the screen serving to keep the ions apart. 

 Ostwald at first preached a similar doctrine, arguing — as in 

 the above quotation — that it gave space in which the dissociation 

 could take place. In 1885 and again in 1886, as well as on 

 several later occasions, I took exception to this view and insisted 

 that solvent and solute were reciprocally affected. Gradually 

 this was realised by the dissociationists but they quietly hedged 

 and never had the grace to admit that ionic dissociation was 



