486 ‘TRANSACTIONS OF SECTION B. 
7. Report on Wave-length Tables of the Spectra of the Elements and 
Compounds.—See Reports, p. 116. 
8. Report on Dynamic Isomerism.—See Reports, p. 270. 
9. Report on the Study of Isomorphous Derivatives of Benzene 
Sulphonic Acid.—See Reports, p. 272. 
10. Experiments illustrative of the Infllammability of Miatures of Coal 
Dust and Air. By Professor P. Puinuirs Bepson, D.Sc. 
1l. On Substances which form Three different Liquid Phases. 
By Dr. F. M. JAEGER. 
The results now recorded arose originally during an experimental investigation 
into certain theoretical objections which occurred to the author in connection with 
Bomer’s method for detecting the adulteration of animal fats with vegetable 
fats. During this work the series of fatty esters of cholesterol and of Windaus’s 
two phytosterols of Calabar fat were prepared, and the observation of the brilliant 
colour changes which occur on melting the cholesterol esters led to the study of 
the liquid phases of these substances. The colour changes in question occur with 
greatest brilliance with cholesteryl cinnamate, and were demonstrated to the 
audience. 
The colour changes are due to the fact that the substances which exhibit them 
yield on melting several strongly doubly refracting liquid phases; the liquid 
phase stable at higher temperatures is always singly refracting. Lehmann showed 
by the microcrystallographic examination of the caproic ester that two doubly 
refracting liquid phases exist, and that of these one is in metastable equilibrium 
with the solid substance. 
The author has, however, found that in the cases of a number of the esters in 
question three liquid phases occur, and are in perfectly stable equilibrium with 
the solid phase: of the three liquid phases two are doubly refracting, and consist 
of aggregations of liquid erystals, whilst the third is always singly refracting, but 
often much more viscid than the doubly refracting phases. The colour changes 
occur at the transition temperatures, or rather at a few degrees below those 
temperatures, whilst the two liquid layers are separating from each other. 
The transitions of phase are in many respects analogous to those occurring 
with polymorphous substances, so that stable and metastable equilibria and 
therefore also cases of monotropy and enantiotropy occur. It is, however, 
remarkable that a new kind of equilibrium is observed with these substances ; 
this the author terms ‘prostable equilibrium.’ A prostable phase resembles a 
metastable phase in that both can be experimentally realised only as the result 
of a temperature change in one direction; the two kinds of phase differ in that 
the prostable phase can only be obtained as a result of raising the temperature, 
The formation of a prostable phase therefore occurs before and after that of the 
stable phases during a rise of temperature. This was demonstrated to the audience 
with the aid of cholesteryl laurinate and illustrated by means of the vapour- 
tension curve of the ester. 
With some of these esters the author has further observed that the solid phase 
can be heated to above the melting-point without melting ; cholesteryl laurinate 
can thus be heated to five degrees above the highest transition temperature 
without the solid phase entirely disappearing. Similar retardation phenomena 
occur in other cases, and their occurrence can be conveniently illustrated by means 
of the vapour-tension curves of the o-phytosterol esters. 
