1236 CHOLESTERIN. 



The crystals are insoluble in ammonia and acetic acid, but 

 readily soluble in hydrochloric or other mineral acid, also 

 slightly so in solutions of acid phosphates and urates of sodium. 

 The above characteristics serve to identify this salt, but in 

 practice the microscopical appearance is usually of most use. 



Succinic acid. COOH . CH 2 . CH 2 . COOH. 



This is the third acid of the oxalic series, being separated from 

 oxalic acid by the intermediate malonic acid, CH 2 (COOH) 2 . 

 It may occur in the spleen, the thymus, and thyroid bodies, 

 hydrocephalic and hydrocele fluids. It has also been stated to 

 occur normally in urine, but this is very doubtful, as also is 

 the statement that it is found in this excretion after taking 

 food rich in asparagin, e.g. asparagus. It is obtained as a 

 product of the putrefaction of proteids. 



Succinic acid crystallizes most usually in the form of large 

 four-sided prisms, occasionally as rhombic tables. It is soluble 

 in about 20 parts of cold water, much more so in hot; it is also 

 soluble in alcohol, more especially if hot, and is but very 

 slightly so in ether. 



The crystals melt at 180 C., and boil at 235 C., being at 

 the same time decomposed into the anhydride and water. The 

 alkali salts of this acid are soluble in water, insoluble in 

 alcohol and in ether. 



Some of the amido-derivatives of succinic acid, viz. asparagin 

 and aspartic acid, are of considerable interest; they will be 

 described later on. 



Cholesterin. C 26 H 44 O or C^ 7 H 46 O. 



This substance is described here rather for the sake of 

 convenience than from its possessing any relationship to those 

 which have preceded it. 



Cholesterin is the only alcohol which occurs in the human 

 body in the free state. (The triatomic alcohol glycerin is always 

 found combined as in the fats; and cetyl-alcohol is obtained 

 only from spermaceti.) It is a glittering white crystalline 

 substance, soapy to the touch,, crystallizing in fine needles from 

 its solution in ether, chloroform or benzene; from its hot alco- 

 holic solutions it is deposited on cooling in rhombic tables; 

 this is the characteristic form and of great importance for the 

 identification of cholesterin. 



When dried it melts at 145, and distils in closed vessels 

 at 360. It is quite insoluble in water and in cold alcohol, 

 but soluble in solutions of bile salts. 



Solutions of cholesterin possess a left-handed rotatory action 



