CHOLIC ACID. 103 



centrated baryta water for some time, allow to cool, 

 separate off the crystalline mass and heat it with 

 hydrochloric acid. The cholic acid will then separate 

 as a glutinous resin. Allow to stand, decant the 

 solution of baryum chloride, wash the resinous mass 

 well with water, dissolve in boiling alcohol, and leave 

 the solution to crystallise. Separate the colourless 

 glassy crystals. 



2. Ascertain their slight solubility in water, greater 

 solubility in ether, and great solubility in boiling 

 alcohol. 



3. Expose them to dry air under the receiver of 

 the air-pump over sulphuric acid ; observe that they 

 lose water of crystallisation and disintegrate. 



4. Take a small quantity of the acid and treat with 

 a drop of solution of cane-sugar, adding concentrated 

 sulphuric acid until the acid is entirely dissolved. On 

 standing for a short time the mixture will assume a 

 purple colour. This test, known as Pettenkofer's, is 

 also produced by the glyko- and tauro-cholic acid, and 

 these yield it probably by virtue of their decomposition 

 liberating cholic acid. See spectrum, p. 74. 



5. Boil cholic acid with nitric acid for a long time, 

 and obtain cholesteric acid from the mother liquor. As 

 the same acid is obtained from cholesterine by the same 

 process, it is probable that cholic acid and cholesterine 

 have the same radical in common. 



Chondrine. 1. Boil cartilage from a young subject 

 in water in an open vessel during twenty- four hours, 

 or in a Papin's digester under pressure at 120 (/. 



