788 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1913. 



Gibbs has given rise to some exaggerations, that one may eyen in the 

 most complicated labyrinth of heterogeneous equilibrium discover 

 the right way without having recourse to the theory of phases, that 

 all the individual cases involved can be solved without one's being 

 obliged to state the law — all that is indisputable, and van't Hoff has 

 furnished a practical demonstration of it ; but it is no less indisputa- 

 ble that there is a gTeat utility in the fact that the particular types 

 and the rules relating to them may be united into one body without 

 one's being obliged to find them again each time, the scheme being 

 capable of great usefulness not only for classification, but because it 

 furnishes a convenient guiding thread in research, especially to those 

 who have not the breadth of mind of a van't Hoff. 



Van't Hoff was a faithful partisan of the atomic and molecular 

 theory. One could expect nothing else from the founder of stereo- 

 chemistry. Friend and companion of Ostwald in the struggles for 

 the modern physiochemical theories, he separated from him when 

 the latter declared war on the atomistic theory in the name of the 

 energetic, not only by doubting the real existence of atoms and 

 molecules, but by denying the possibility of ever demonstrating 

 this existence, and disputing even the advantage of the use of the 

 atomic theory as an instrument of work. When the campaign of 

 Ostwald, which a prompt defeat awaited, was in full swing, van't 

 Hoft' gave, in 1906, in Vieimaj a lecture in which, without departing 

 from his calm and serene tone, he put people on guard against the 

 dangers of this movement and affirmed once more his conviction 

 that the atomic theory was still destined to render great service to 

 science. 



Of the two courses which physical chemistry can pursue he fol- 

 lowed the chemical one. As a chemist he was always interested in 

 the substances themselves, the physical properties interesting him 

 only as characteristics of the substances, and the general laws them- 

 selves, as well as the physical and mathematical methods, interesting 

 him only as more perfect means toward the investigation of their 

 nature — a means permitting one to give of the infinite variety of 

 the latter a quantitative and more exact expression than could be 

 obtained with the vague concepts and inexact methods of traditional 

 chemistry. On the other hand, what interests the physical chemists 

 of the other wing, as well as the pure physicists, is above all, the 

 properties in themselves, the substances appearing to them only as 

 the inevitable bearers of these properties. 



In any case it is certainly no injustice to even the most famous 

 physicochemists of his generation to say that he was head and 

 shoulders above them. If one wants to find men whose worth is 

 comparable to his one must go further back to the heroic times when 



