HANDBOOK FOR BIO-CHEMICAL LABORATORY. 51 



leum ether, which removes the benzole acid, oxyacids, fat, and 

 phenol, while the hippuric acid is left undissolved. The 

 residue is dissolved in a little warm water, treated with 

 animal charcoal, and evaporated at 50-60 C. to point of 

 crystallization. (Bunge and Schmiedeberg.) 



Synthetical Hippuric acid may be prepared by adding a 

 few drops caustic-soda solution to a watery solution of glyco- 

 coll, shaking with benzoyl chloride, adding gradually an ex- 

 cess thereof and then making strongly alkaline with caustic 

 soda. Now precipitate with hydrochloric acid on cooling. 

 The precipitate of hippuric and benzoic acids are carefully 

 drained, pressed between filter-paper and washed with cold 

 water, dried, and extracted with petroleum ether, which only 

 dissolves the benzoic acid. The remaining hippuric acid is 

 recrystallized from hot water. (J. Baum.) 



Properties. Hippuric acid crystallizes in semi-transparent, 

 milk-white, long, four-sided rhombic prisms or columns, or 

 in needles on rapid crystallization. They dissolve in 600 

 parts cold water, but more easily in hot water. It is soluble 

 in alcohol, but with difficulty in ether. It is insoluble in 

 petroleum ether, benzol, and carbon disulphide. Hippuric 

 acid is readily soluble (about 12 times) in acetic ether. It 

 combines with bases, forming salts which are soluble in water 

 or alcohol. The combinations with the alkalies and the alka- 

 line earths are readily soluble in alcohol, while the silver, 

 copper, and lead salts are soluble with difficulty. On boiling 

 with caustic alkalies, mineral acids, or by continued heating 

 with water at 170-180 C. it splits into benzoic acid and 

 glycocoll. 



Allantoin, 



.CH.NH.CO.NH,. 



Preparation. 1. Evaporate the amniotic fluid of a cow to 

 one sixth (-J-) its volume, or calf urine to syrupy consistency, 



