iv OBITUARY NOTICES OF MEMBERS DECEASED. 



of Berlin by the Imperial Academy of Sciences. 



Let us now turn to the work of this very great man. 



Van't Hoff's name will always be associated with the following 

 epoch-making discoveries : 



The founder of the science of stereochemistry. 



The first to apply the law of mass action to chemical reactions in 

 a broad way, and thus to open up the fields of chemical dynamics 

 and equilibrium. 



To have pointed out the close relations between solutions and 

 gases, and thus to have placed the whole subject of solutions upon 

 a scientific basis. 



Van't Hoff, as we have seen, began his scientific career as a pupil 

 of Mulder in Utrecht, of Kekule in Bonn, and of Wiirtz in Paris. 

 During this period he was, therefore, busy primarily with organic 

 chemistry, and let us see the result. At the age of twenty-two, while 

 still a pupil of Mulder in Utrecht, he published in 1874 a short paper 

 of eleven pages in Dutch, which was destined to revolutionize the 

 whole subject of organic chemistry. Organic chemistry, at this time, 

 under the dominating influence of Kekule was concerned chiefly with 

 the question of constitution, but the constitutional formulje then in 

 vogue did not even raise the question as to how the atoms within 

 the molecules are distributed in three dimensions in space. 



The short paper by Van't Hoff in Dutch had to do with the tre- 

 mendous, and apparently hopeless problem of the arrangement of the 

 atoms in the molecules in space. The following year (1875) this 

 paper was translated into French, bearing the title " La Chimie dans 

 I'Espace," and two years later into German, with a preface by Wisli- 

 cenus, " Die Lagerung der atome im Raume." Let us glance briefly 

 at the contents of this paper. 



It had been shown by the work of Henri and others that methane, 

 or marsh gas (CH^), is a symmetrical compound, /. c, all of the 

 four hydrogen atoms bear the same relation to the carbon atom. 

 Van't Hoff pointed out that this fact alone forces us to conclude that 

 methane must be represented in space by the regular tetrahedron ; 

 the carbon atom being at the center of the tetrahedron and the four 

 hydrogen atoms at the four solid angles. This is the only geomet- 



