1202 



duced, for that the double binding can exert- a very divergent 

 influence on the refraction, and especially on the dispersion of 

 unsaturate compounds. 



Among the posthumous papers there were the refractometric 

 determinations of more than 350 compounds, which had not yet 

 been published, among which almost complete series of liomologues. 

 That Eykman did not publish these himself I attribute chiefly to the 

 fact that he could less and less bring himself to prepare his results 

 for the press. Possibly, too, he wished to wait till some series had 

 become still more complete, or to repeat some measurements before 

 their publication. In view of these surmises it may seem somewhat 

 bold to make results public which the master himself thougiit fit 

 to withhold still. Besides, however, the fact mentioned just now, 

 there is another circumstance that justifies publication. It is the 

 comparison of the measurements made at the same substances which 

 were carried out by hiui in many successive years. Then there appears 

 to exist an almost perfect agieement in the values in almost all 

 cases. In fact all his work gives the impression of having been 

 executed with scrupulous care, also as regards the purity of the 

 compounds. 



It is to be regretted that the material left behind consists almost 

 exclusively of tables, without any commentary. 1 have tried to supply 

 this defect by adding a review to every series of measurements of 

 homologues, for the rest fully realising the difficulty of this task, 

 which certainly would have been accomplished by the master him- 

 self in a much better way. I have set myself the task to interpret 

 the results in these reviews as much as possible in the same spirit 

 as speaks from Eykman's works, which often give evidence of 

 entirely different views from those embraced by most chemist who 

 work in this field, in the hope that those who are more competent 

 in this kind of researches will judge that I have succeeded in giving 

 the right interpretation. 



The measurements left behind comprise compounds from the fol- 

 lowing homologous series: saturate hydrocarbons, alcohols C„H„2i+0H, 

 alkylhaloids, aliphatic and cyclic amines, acid C„H2„02 and their 

 esters, saturate aldehydes and ketones, unsaturate hydro-carbons, 

 unsaturate acids, plurivalent alcohols, pluribasic acids, hydroxy-acids, 

 aldehydic and ketonic acids, derivatives of carbonic acid, cyclic 

 compounds, aromatic hydro-carbons, phenols, aromatic amines and 

 aromatic acids. 



This posthumous material confirms on one side for the greater 

 part the conclusions at which Eykman had already arrived by the 



