72 PROPERTIES OF CERTAIN AMINO-ACIDS. [CH. IV. 



78. Glycine. 



A. The preparation of glycine ester hydrochloride from gelatin. 



(i.) To 300 cc. of pure concentrated hydrochloric acid in a 

 round-bottomed flask add 100 grams, of ordinary glue. 



(ii.) Heat on a boiling water bath, with occasional shaking, until 

 the glue has dissolved.. 



Fig. 7. Heating on a sand bath under a reflux condenser. 



(iii.) Boil the mixture on a sand bath under a reflux condenser 

 for four hours (see fig. 7). 



(iv.) Transfer the dark product to a litre distilling flask, and 

 distil off the acid as completely as possible in vacuo, 

 using the apparatus shewn in fig. 8. The fluid is placed 

 in flask A, which is immersed in a water bath maintained 



