Chemistry. — "Eykman's Refractometric Investigations, in Connection 

 loitli the Presentation of the Edition of his Works." By Prof. 



A. F. HOLLEMAN. 



(Communicated in the meeting of January 25, 1919). 



Though Eykman devoted about twenty-five years of his life to 

 refractometric investigations of oiganic compounds, and collected 

 ill the course of these researches a tremendous amount of material, 

 arriving at very important conclusions from this material, his work 

 in this interesting region has, nevertheless, remained pretty well 

 unknown. This is chiefly owing to the way in which he published it. 



At first choosing for this puipose the Berichte der deutschen 

 chemischen Gesellschaft, he afterwards wrote a number of treatises 

 in the Recueil : but by far the greater part of his papers appeared 

 exclusively in the Chemische Weekblad. 



The researches of his pupils were up to now only laid down in 

 Theses for the Doctorate. 



For foreign chemists, who are only by exception conversant with 

 the Dutch language, it was, therefore, practically impossible, to get 

 acquainted with Eykman's researches. 



It further appeared, when his posthumous papers were put into 

 my hands by his brother, our felhiw-member Chr. Eykman, that these 

 contained still a voluminous material of facts which had not yet 

 been published at all. 



In order to render his ideas and experimental results more 

 generally accessible, it was necessary to collect his refractometric 

 researches and publish them as a wiiole. This publication has been 

 rendered possible by the financial help of the Hollandsche Maat- 

 schappij der Wetenschappen, which in this has proved itself worthy 

 of its high traditions. 



In the now published work: Recherches réfractométriques de feu 

 J. F. Eykman, are found in the first place a biography and a sum- 

 mary of his researches in this region. Then follow the i)apers from 

 the "Berichte", which contain among others his researches on the 

 displacement of the double bindings in the side chains of aromatic 

 compounds towards the nucleus. This displacement gives rise to a con- 

 siderable increase of the molecular refraction and dispersion. 



