276 LIPOIDS. 



bining cholesterin with any other body, we have no means of con- 

 trolling this formula and of determining its atomic weight. Zwenger 

 has very recently analysed the cholesterilins, of which he was the 

 discoverer, and found them composed in a tolerably uniform man- 

 ner. He assumes, however, that there are differences between them, 

 and that they may be respectively represented by C 32 H 26 , C 22 H 18 , 

 and C 27 H 22 ; and he believes that cholesterin consists of these 

 three carbo-hydrogens and 3 atoms of water, its formula being, 

 according to his views, C 81 H 69 O 3 . Taking into consideration the 

 limited accuracy which we are capable of attaining in our elemen- 

 tary analyses, and the method by which we deduce a formula from 

 empirical results, we must regard Zwenger's view as, at present, 

 very hypothetical. 



We give the composition of cholesterin according to both 

 formulas : 



Carbon 37 atoms 84'733 81 atoms 83-93 



Hydrogen 32 12'214 69 11.91 



Oxygen 1 3'053 3 4'16 



100-000 100-00 



Notwithstanding its extraordinarily high numbers, Zwenger's 

 formula accords more closely than the simpler one with the empi- 

 rical results. 



Products of decomposition. . Cholesterilin, C 32 H 265 is earthy, 

 amorphous, insoluble in water, and slightly soluble in alcohol ; it 

 differs from the two other carbo-hydrogens by its insolubility in 

 ether; it crystallises from a hot oil of turpentine solution, and 

 melts and is decomposed at 240. 



b. Cholesierilin, C 22 H 18 , crystallises in minute, strongly glisten- 

 ing plates or delicate needles, which are insoluble in water and 

 alcohol, but soluble in ether; it fuses at 255, and on cooling soli- 

 difies in a crystalline form. 



c. Cholesterilin, C 27 H 22 , is a yellow, amorphous, resinous mass, 

 freely soluble in ether, slightly so in alcohol, and insoluble in water ; 

 it fuses at 127. Both this and the preceding variety are decom- 

 posed by heat. The formulae must be regarded as entirely hypo- 

 thetical, since the per-centage composition, both as found and as 

 calculated, approximates to 88$ of carbon, and 12 of hydrogen for 

 all three of them. 



a. Cholesterone is obtained by extracting with spirit the resi- 

 due of cholesterin, heated with phosphoric acid to 137; it 

 crystallises in right rhombic, bilaterally acuminated prisms ; is 



