II. CHEMISTRY 185 



dehydrated, melted in sealed capillaries at 160° to 163°. The circumstances 

 of heating were not stated, nor was it made clear whether any precautions 

 against oxidation were taken. Tanret-^^ found that purified hydrated ergos- 

 terol in sealed capillaries melted from 4° to 6° lower than in capillaries 

 filled with carbon dioxide or than it did on the Maquenne block,^^^ which 

 minimizes oxidation by rapid heating. He gave the melting point as 165°. 

 Bacharach et al.-*^ emphasized the importance of rapid heating. They found 

 melting points between 162° and 164° for commercial hydrated ergosterol 

 in open capillaries. Huber et alP^ reported the same range, 162° to 164°, 

 for a purified sample of hydrated ergosterol, but did not specify how the 

 determinations were made. Bills and Honeywell-^^ observed that the point 

 at which molten purified ergosterol in sealed capillaries becomes clear de- 

 pends upon the water content. The clearing points (in distinction from the 

 liquefying points given by others) ranged from 166° to 183°, according to 

 the degree of hydration. 



The turbidity associated with moisture may be related to the phenome- 

 non of mesomorphism described by FriedeP^^ and noted by Gaubert^^^- ^" 

 in ergosterol complexes ("liquid crystals"). Certainly it makes difficult the 

 observation of the true melting point, for it lengthens the apparent melting 

 range, thus more or less offsetting the depressing effects of oxidation. All 

 facts considered, one must conclude that the melting point of ergosterol 

 should be taken in the open to facilitate the escape of water, and rapidly 

 to minimize oxidation. Tanret's value of 165° on the Maquenne block is 

 perhaps the best determination so far recorded. 



The melting points of thirty ergosterol esters are given in Table IV. 

 Many of these esters, and others studied by Gaubert,"^ exhibit melting 

 point anomalies associated with mesomorphism. It is probable, moreover, 

 that the single melting points ascribed to certain other esters in the table 

 represent only the final, or clearing, points, the authors having neglected 

 to note earlier phases. Thus, Tanret-^^ gave the melting point of ergosteryl 

 butyrate simply as 129.5°, whereas Gaubert, working later with the same 

 specimen of this ester, recorded a spread of 28° between the liquefying and 

 clearing points (100° to 128°). Besides the esters, there are several loose 

 combinations of ergosterol with glycerol, orcinol, urea, and substituted 

 ureas, which exhibit more or less extended turbid phases in their melt- 

 ing."®' 2" It is well known that mesomorphic states are exhibited by numer- 

 ous esters and complexes of cholesterol and other sterols, as well as ergos- 

 terol. However, with the ergosterol compounds, the viscous, or smectic, 



2" L. Maquenne, Bull. soc. chim. France Ser. 2, 48, 771 (1887). 



"5 G. Friedel, Ann. phys. Ser. 9, 18, 273 (1922). 



"6 p. Gaubert, Bull, soc.frang. mineral. 32, 62 (1909). 



2" P. Gaubert, Com-pt. rend. 149, 608 (1909). 



