CHAP. IV.] 



GLYCOCINE. 



309 



composition, by acids and alkalies, of glykocholic acid, of hyoglyco- 

 cholic acid a-nd of hippuric acid. It is also one of the products of 

 decomposition obtained when gelatine is subjected to long boiling 

 with barium hydrate, or with dilute sulphuric acid, as well as when 

 it undergoes digestion by trypsin. It is also yielded when fibroin 

 (one of the constituents of silk) is subjected to Schtitzenberger's 

 process, and when spongin is boiled with dilute sulphuric acid. 



1. From glykocholic acid. Pure glykocholic acid 

 is added to a saturated solution of barium hydrate 

 and the mixture boiled in a flask with an inverted 

 condenser for eight hours (see fig. 20). The liquid having been 

 allowed to cool, sulphuric acid is added to it ; this precipitates both 

 cholalic acid and barium. The filtrate containing an excess of 

 sulphuric acid is heated with pure barium carbonate, and then 

 filtered. The filtrate is concentrated and set aside to crystallize. 



Modes of 

 preparation. 



FIG. 20. FLASK, PLACED ON SAND BATH, AND FITTED WITH AN INVERTED CONDENSER. 



2. From hippuric acid. Glycocine is most economically as well 

 as most readily obtained by decomposing hippuric acid (benzoyl- 

 amido-acetic acid), by boiling it with hydrochloric or sulphuric acids. 

 The reaction which occurs is represented by the following equation : 



C 6 H 6 . CO.NH.CH 2 .COOH + H 2 = C 6 H 5 .COOH + CH 2 . NH 2 .COOH 



Hippuric acid. 



Benzoic acid. 



Glycocine. 



