EXAMINATION OF THE URINE. 



105 



consistency, precipitate with alcohol, filter, evaporate the 

 alcoholic extract and, when perfectly cold, acidify strongly 

 with hydrochloric acid. The hippuric acid separates as a 

 crystalline paste. Filter this off (keeping the filtrate), 

 wash, drain by pressing between drying-paper, dissolve in 

 water to which ammonia has been added, decolorize by boil- 

 ing with some bone-black, filter, concentrate, precipitate 

 again by adding hydrochloric acid, filter, wash and dry on 

 drying-paper in the air. Examine a small portion while still 

 moist under the microscope. If it proves to be contaminated 

 with benzoic acid (irregularly indented leaflets, see Fig. 10), 



~~ 6 



FIG. 10. a, benzoic acid; b, hippuric acid. 



treat the dry mixture of acids with ether to dissolve the ben- 

 zoic acid. In order to obtain larger crystals the acid may 

 be recrystallized from hot water. 



Reactions of Hippuric Acid. 



1. A small portion is heated in a test-tube with water: it 

 dissolves. On cooling the hippuric acid separates in needles. 

 Examine under the microscope. 



2. Heat a small portion in a test-tube: the hippuric acid 



