122 RESINOUS ACID. 



when oleic acid was similarly treated), and besides these, a heavy, 

 stupifying oil, which, when treated with alkalies, was decomposed 

 into nitrocholic acid and cholachrole ; while in the retort there 

 remained, as if proof against the further action of nitric acid, oxalic, 

 choloidanic and cholesteric acids. 



Cholacrole, C 8 H 5 N 2 O 13 , is a yellow oil with a pungent, over- 

 powering, cinnamon-like odour, dissolving readily in alcohol and 

 ether, but difficult of solution in water ; it is indifferent towards 

 both acids and alkalies, and is decomposed at 100 with the deve- 

 lopment of nitrous acid, and sometimes with slight decrepitation. 



Nitrocholate of potash, KO.C 2 HN 4 O 9 , occurs in lemon-yellow, 

 square tablets, has a faintly overpowering odour, decrepitates at 100, 

 is decomposed when boiled with water, and is not precipitated by 

 metallic salts. 



On pouring into a large test glass the thick, brownish yellow 

 mass which remains in the retort, it separates on cooling into two 

 layers, of which the upper is frothy, and consists of crystals of cho- 

 loidanic acid, while the lower is of a yellowish brown colour, acid 

 and bitter. 



Choloidanic acid, C 16 H 12 O 7 , crystallises in satiny, hair-like 

 prisms ; when dry, it resembles asbestos ; it is difficult of solution 

 even in hot water, but dissolves freely in alcohol; it reddens 

 litmus, and is decomposed at a high temperature, but is unaffected 

 by hydrochloric or nitric acid. Its salts, even those of the alkalies, 

 are insoluble or difficult of solution, and do not crystallise. 



In this yellowish brown mother-liquid there are also contained 

 oxalic acid, a resinous mass, and cholesteric acid. 



Cholesteric acid, C 8 H 4 O 4 .HO, occurs as a light yellow mass, 

 resembling cherry-gum ; it has a well-marked acid and bitter taste, 

 abstracts water from the air, dissolves both in water and in alcohol, 

 the solution being of a yellow tint, and decomposes when heated 5 

 its compounds with alkalies and alkaline earths do not crystallise, 

 and are soluble in water, but its compounds with metallic oxides 

 are insoluble. The silver-salt dissolves in boiling water, from 

 which it is deposited, on cooling, in crystalline incrustations. 



Preparation. Cholic acid, which occurs in the bile conjugated 

 with nitrogenous bodies, is most readily obtained by boiling the 

 resinous masses precipitated by ether from the alcoholic solution 

 of the bile with a dilute solution of potash for twenty-four to thirty- 

 six hours, till the potash-salt that has separated begins to crystallise. 

 The potash-salt must then be dissolved in water and the acid 

 removed from it by hydrochloric acid. By the addition of a few 



