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did colour-phenomena observed during the ('oolin;^; of the clear, 

 isotropou'ï, fused mass to its temperature of soliditication, and also 

 during the heating in the reverse way. Tiiese colour phenomena are 

 caused by interference of the incident light, every time the turbid 

 anisotropous liquid-phase occurs, or passes into the isotropous liquid. 

 During this last transition we notice while stirring with the ther- 

 mometer, the "oily slides" formerly described by Reinitzer, until the 

 temperature t.-^ has been exceeded. These colours also occur when 

 the solid phase deposits from the anisotropous liquid, therefore below 

 t^. The most brilliant, unrivalled violet and blue colour display is 

 sliown by the butyrate and normal \alerate, also \ery well by the 

 capronate and caprinate. 



The temperatures in \_] t^ answer to anisotropous liquid phases 

 which are labile in regard to the isotropous liquid, and irliich double- 

 refracting liquids are, therefore, only realisable in undercooledfused 

 material. Of this case, which is comparable with the monotropism, as 

 distinguished by LehmaN!* from the case of enantiotropous transfor- 

 mations, the acetate is the only known example up to the present. Xoav 

 the number of cases is increased by three, namely the formiat>>, the 

 caprylate and without any doubt also the isovalerate, to w^hich I will 

 refer presently. Cholesterol-formiate and caprylate melt therefore, 

 perfectly sharply to a clear liquid at, respectively 96^',° and 106. °2. 

 If, however, the clear liquid is suddeidy cooled in cold water, 

 one notices the appearance of the turbid, anisotropous, more-labile 

 phase, accompanied by the said colour phenomena. The acetate in 

 particular exhibits them with great splendour. It is quite possible 

 that many organic compounds which are described as "melting 

 sharply", belong to this category and on being cooled suddenly 

 possess a double-refracting liquid phase, even although this may last 

 only a moment. The phenomenon of liquid crystals would then be 

 more general than is usually believed. 



Prof. Lehmann, to whom I have forwarded a little of the cholesterol- 

 esters, has been able to fully verify my observations. This investigator 

 has, in addition, also found that cholesterol-caprinate may probably 

 exhibit two anisotropous liquid phases. Although, personally, I never 

 noticed more than one single phase, and Prof. Lehmann's determinations 

 are only given provisionally, this case would certainly have to be 

 regarded as one of the most remarkable phenomena which may be 

 expected in a homogeneous body, particularly because the percep- 

 tibility of those tiro phases implies that they would not be miscible 

 in all proportions with each other. 



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