686 URINE. 



assumption, where he used benzoylated higher ammo-acids, have not 

 given support to this assumption, and the question how the abundant 

 formation and elimination of glycocoll take place is still unexplained. 



The kidneys may be considered in dogs as special organs for the syn- 

 thesis of hippuric acid (SCHMIEDEBERG and BUNGE *). In other animals, 

 as in rabbits, the formation of hippuric acid seems to take place in other 

 organs, such as the liver and muscles. The synthesis of hippuric acid is 

 therefore not exclusively limited to any special organ, though perhaps 

 in some species of animals it may be more abundant in one organ than in 

 another. 



Properties and Reactions of Hippuric Acid. This acid crystallizes in 

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

 or in needles by rapid crystallization. They dissolve in 600 parts cold 

 water, but more easily in hot water. They are easily soluble in alcohol, 

 but with difficulty in ether. The acid dissolves more easily (about 12 

 times) in acetic ether than in ethyl ether. Petroleum-ether does not 

 dissolve hippuric acid. 



On heating hippuric acid it first melts at 187.5 C. to an oily 

 liquid which crystallizes on cooling. On continued heating it decom- 

 poses, producing a red mass and a sublimate of benzoic acid, with the 

 .generation, first, of a peculiar pleasant odor of hay and then an odor 

 of hydrocyanic acid. Hippuric acid is easily differentiated from benzoic 

 acid by this behavior, also by its crystalline form and its insolubility in 

 petroleum ether. Hippuric acid and benzoic acid both give LUCRE'S 

 reaction, namely, they generate an intense odor of nitrobenzene when 

 evaporated to dryness with nitric acid and when the residue is heated 

 with sand in a glass tube. Hippuric acid in most cases forms crystal- 

 lizable salts, with bases. The combinations with alkalies and alkaline 

 earths are soluble in water and alcohol. The silver, copper, and lead 

 salts are soluble with difficulty in water; the ferric salt is insoluble. 



Hippuric acid is best prepared from the fresh urine of a horse or cow. 

 The urine is boiled a few minutes with an excess of milk of lime. The 

 liquid is filtered while hot, concentrated and then cooled, and the hippuric 

 acid precipitated by the addition of an excess of hydrochloric acid. The 

 crystals are pressed, dissolved in milk of lime by boiling, and treated as 

 above; the hippuric acid is precipitated again from the concentrated 

 filtrate by hydrochloric acid. The crystals are purified by recrystalliza- 

 tion and decolorized, when necessary, by animal charcoal. 



The quantitative estimation of hippuric acid in the urine may be 

 performed by the following method (BUNGE and SCHMIEDEBERG 2 ) : 



1 Arch. f. exp. Path. u. Pharm., 6; also A. Hoffmann, ibid., 7, and Kochs, Pfluger's 

 Arch., 20; Bashford and Cramer, Zeitschr. f. physiol. Chem., 35. 



2 Arch. f. exp. Path. u. Pharm., 6. In regard to other methods, such as Blumen- 



