JACOBUS HENRICUS VAN'T HOFF 95 



JACOBUS HENRICUS VAN'T HOFF 



By Professor HARRY C. JONES 



JOHNS HOPKINS UNIVERSITY 



THE death of Van't Hoff removes one of the leading men of science 

 not only of this age, but of all time. 



Born in Rotterdam in 1852, the son of a physician, he received his 

 early training in the Bealschule in Rotterdam and in the Polytech- 

 nikum in Delft. At twenty he had completed his work in the Univer- 

 sity of Leiden. He then studied under Kekule in Bonn and Wiirtz in 

 Paris, and obtained the Doctor's degree at Utrecht, at the age of 

 twenty- two. 



Van't Hoff, in 1876, was appointed privatdozent in physics in the 

 veterinary college in Utrecht. In 1877 he was called to Amsterdam as 

 lecturer in chemistry, and was appointed professor of chemistry in 

 1878, a position which he held until 1896, when he accepted a call to a 

 chair created for him at Berlin. He held this chair and was also a 

 member of the Berlin Academy of Sciences until his death on March 

 1, 1911. 



Van't Hoff did three great things. His early work was with 

 Mulder in Utrecht, Kekule in Bonn and Wiirtz in Paris, and therefore, 

 in organic chemistry. He raised and answered the question, what is 

 the arrangement in three dimensions in space of the atoms in the 

 simpler compounds of carbon? Henri had shown that the four 

 hydrogen atoms in marsh gas (CH 4 ) all bear the same relation to the 

 molecule. The geometrical configuration of this molecule follows of 

 necessity from this fact. The only geometrical form in three dimen- 

 sions in space fulfilling the condition of a central object surrounded 

 symmetrically by four things of the same kind, is the regular tetrahe- 

 dron. Thus arose the theory of the " tetrahedral carbon atom." 



Some compounds of carbon rotate the beam of polarized light to the 

 right, others to the left — are " optically active," as they are termed. 

 Pasteur had pointed out that this is possible only in compounds in 

 which there is some kind of asymmetry. Van't Hoff showed in what 

 the asymmetry consisted. He showed that all optically active com- 

 pounds of carbon then known contain a carbon atom in combination 

 with four different atoms or groups, and the same holds true to-day. 

 Such a carbon atom is known as an " asymmetric carbon atom," and 

 thus arose the theory of the "asymmetric tetrahedral carbon atom," 



