( 485 ) 



'continuously. At about 97. °5 the liquid is clear and isotropous; it 

 has then the thickness of paraffin-oil. 



It', however, the isotropous fused mass is eooled, t he isotropous 

 paraffin-oil-like liquid remains clear to about 87. °3, when a turbid 

 doubly-refracting phase is formed. This, on further cooling, gradually 

 becomes more viscous; at 80° it is as thick as butter, at 66° it can 

 hardly be stirred, and may be drawn into threads. It may be cooled 

 to the temperature of the room without solidifying. It remains in 

 this condition for hours, but after 24 hours it has again become 

 crystalline. The substance, therefore, has no determinable melting 

 or solidifying point. 



I). a-Phytosterol-Isovalerate behaves quite analogously to the n- 

 valerate. Neither a definite melting point, nor a solidifying point can 

 be observed. The mass softens at about 45°, is anisotropous thick- 

 fluid at 65°, and becomes clear and isotropous at 81°. 



On cooling to 78. °J, a beginning of turbidity is noticed, the liquid 

 gradually becomes thicker and is converted at an uncertain temperature 

 into a tenacious sticky, doubly-refracting mass, which after 24 hours 

 has again soliditied to a crystalline mass. 



§ 3. The thermometrical behaviour of these remarkable substances 



is represented in the annexed schematic /^-/-diagram, for the case 

 of the n-butyrate and isobutyrate. The typical irreversibility of these 

 phenomena is thus seen at once. Moreover in the case of the two 

 valerates, the whole behaviour can be described only as a real, 

 gradual transformation, solid ^f liquid with an intermediate realisation 

 of an indefinite number of optieally-anisotropous liquids. 



§4. The micro-physical behaviour of the fatty «-phytosterol 

 esters. Perhaps, there are no substances known, which exhibit under 

 the microscope the characteristic phenomena of anisotropous liquids 

 in so beautiful and singular a manner as these esters; in this respect 

 the isobutyrate and the valerate excel in particular. In the normal 

 butyrate, the traject, where the liquid crystals are capable of exis- 

 tence is rather too small. For this reason, although the behaviour of 

 the four substances differs in details, I will describe more particularly 

 the behaviour of the «-valerate and as to the others, 1 will state 

 occasionally in what respect they differ from the valerate. In conse- 

 quence of the totally different circumstances which the microscopic 

 method involves, nothing more is seen of the thermically observed 

 peculiar irreversibility and even progression of the transformations. 

 For the study of the nature of the diverse phase-transformations, the 



