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Chemistry. — "On the anisotropous liquid phases of the butyric 

 ester of dihydrocholesterol, and on the question as to the 

 necessary presence of an ethylene double bond for the occur- 

 rence of these phenomena''. By Dr. F. AI. Jaeger. (Communi- 

 cated by Prof. A. P. N. Fkanchimont). 



(Communicated in the meeting of February 23, 1907). 



§ J. In order to explain the behaviour of substances which arc 

 wont to exhibit double-refracting liquid phases, some investigators 

 have started the hypothesis that, in this kind of organic substances, 

 it might be a question of systems formed of two components, and 

 of equilibrium phenomena between tautomeric and isomeric modifica- 

 tions, which would be converted into each other with finite velocity. 



Although it is difficult to understand how such a supposition, 

 which is easy to propound, but very difficult to prove, could explain 

 the numerous well ascertained facts of the regular optical an isotropism 

 of these phases, it might explain, however, at least to some extent, 

 the peculiar irreversible transitions of phases, which I found more 

 particularly with the esters of cholesterol and «-phytosterol, and also 

 the hindrance phenomena noticed on that occasion *). 



Such a supposition, however, is perhaps of some importance for 

 the interpretation of the brilliant colour phenomena which accompany 

 the phase-transitions in the cholesterol esters. For a mixture, or an 

 emulsion of substances, whose indices of refraction differ very little, 

 but whose dispersions differ much, might, like Christhiansen's mono- 

 chromes, cause a similar display of colours. 



§ 2. There is more than one cause for tautomerism (or isomerism) 

 in the case of these cholesterol esters, for all the esters, as well as 

 cholesterol itself, possess an asymmetric carbon atom, and in solution 

 they all polarise to the left. 



Consequently, a racemisation during the esterification is by no 

 means excluded, and we might, therefore, have a mixture of the 

 optical antipodes. Cholesterol, moreover, possesses an ethylene double 

 bond, so that we may also expect an isomerism in the sense of* 

 fumaric and maleic acids. 



§ 3. As many other compounds (in fact most organic substances 

 which are wont to exhibit these phenomena of doubly refracting 



] > F. M. Jaeger, These Proc. 1900 p. 472 and 483 (29 December). 



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