476 J. H. van't Hoff on the Origin 



occurred to me that I might conveniently start from one of 

 two centres. It was open to me to give an account either of the 

 investigations on double salts and the limits of their existence, 

 or of the theory of dilute solutions and osmotic pressure. As 

 I had no desire to introduce a topic which might prove un- 

 welcome to the members of the Society, I remitted the choice 

 of the subject to the committee. Although I had half hoped 

 it would be otherwise, they expressed themselves in favour of 

 the theory of solutions, but in giving an account of this sub- 

 ject I have promised to avoid everything of a polemical 

 nature. Another reason which would have induced me to 

 eschew this subject is that, in outline at least, it is already 

 familiar to most of you ; consequently, a simple exposition 

 would be mere repetition. I think, therefore, that it would 

 be better to consider for a short time the origin of the theory 

 of solutions; not for the purpose of espousing claims of 

 priority, but rather to disclose how the train of ideas deve- 

 loped in my mind, so that finally the opponents can also say 

 " Dass alles wissen, alles vergeben ist." 



All my opinions in regard to the " position of the atoms in 

 space," which were only a structure founded on the relation- 

 ship between a physical property, viz. optical activity, and 

 chemical constitution, began to germinate when I commenced 

 the study of chemistry under Kekule and Wislicenus. Young 

 as I was at that time, I wished to determine the relation 

 between constitution and chemical properties, for a con- 

 stitutional formula should express the complete chemical 

 behaviour of a substance. 



This was the origin of my work Ansichten uber die organ- 

 ische Chemie, which is possibly not known to you. It little 

 matters. It was only of value to me in so far as it clearly 

 indicated a gap in our knowledge. As is well known, the 

 oxygen in organic compounds exercises an accelerating action 

 on almost alt changes ; for example, the oxidation of methane 

 is more difficult than the oxidation of methyl alcohol, and so on. 



An accurate knowledge of the velocity of reactions was 

 thus rendered necessary, and this consequently gave rise to 

 my work Etudes de dynamique chimique. The study of che- 

 mical equilibrium, which depends on the equality of two 

 opposed reactions, naturally accompanied that of the velocity 

 of reaction, and was placed on a sure basis by its connexion 

 with thermodynamics. As often happens, in trying to reach 

 my goal I was getting farther and farther from it. And 

 since the question of equilibrium is intimately connected with 

 the problem of chemical affinity, I first of all encountered a 



