vi OBITUARY NOTICES OF MEMBERS DECEASED. 



reacting substances not only conditions the velocities of chemical 

 reactions, but often even the direction or nature of the reaction. 

 The effect of mass on chemical reaction was given simple algebraic 

 expression in 1867 by the Norwegian mathematical physicist Guld- 

 berg, and the Norwegian chemist, his son-in-law, Waage ; both of 

 the University of Christiania. 



It remained here again for \*an't Hoff to demonstrate the real 

 importance of the law of mass action. He showed that chemical 

 dynamics in general, and the conditions that obtain when chemical 

 equilibrium is reached, can all be dealt with by the law of mass 

 action. In this work the whole subject of chemical dynamics and 

 equilibrium was reduced to a science, and whatever has been subse- 

 quently done in this field has felt the influence of this early work 

 by Van't Hoff. 



The results, both dieoretical and experimental, obtained by Van't 

 Hoff and his co-workers, were published in the well-known volume 

 •^ fitudes de Dynamique chimique " in 1884. In the portion of the 

 work that deals with chemical dynamics, it is shown that the velocity 

 of a reaction is a function of the number of molecules taking part 

 in that reaction ; and a method for determining the " order " of a 

 reaction, or the number of molecules taking part in the reaction was 

 worked out. The effect of temperature on reaction velocity was 

 here discussed, and it was pointed out that chemical reactions are, in 

 general, much more complex than we are usually accustomed to 

 regard them ; a number of " disturbing " factors coming into play. 



The treatment of chemical equilibrium is quite as important as 

 that of chemical kinetics. The new feature here was the systematic 

 application of thermodynamics to such problems. Before this book 

 appeared there was no scientific treatment of the subject of chemical 

 equilibrium. Van't Hoff showed in this volume the importance; in- 

 deed, the absolute necessity of a physical and mathematical training 

 for every chemist who wishes to go beneath the purely empirical 

 side of his science. 



We come now to the third and greatest contribution of Van't 

 Hoff to chemistry in particular and to science in general, the rela- 

 tions betiveen solutions and gases. 



