362 PHYSIOLOGICAL CHEMISTRY. 



zoic acid by this behavior, also by its crystalline form and its in- 

 solubility in petroleum ether. Hippuric acid and benzoic acid 

 both give LUCRE'S reaction, namely, they generate an intense odor 

 of nitrobenzol when evaporated with nitric acid to dryness and 

 when the residue is heated. Hippuric acid forms crystallizable 

 salts, in most cases, 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 iron- 

 oxide 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 recrystallization 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 SCHMIEDE- 

 BERG) : The urine is first made faintly alkaline with soda, evapo- 

 rated nearly to dryness, and the residue thoroughly extracted with 

 strong alcohol. After the evaporation of the alcohol, dissolve in 

 water, acidify with sulphuric acid, and completely extract by agitat- 

 ing (at least five times) with fresh portions of acetic ether. The 

 acetic ether is then repeatedly washed with water, which is removed 

 by means of a separatory funnel, then evaporated at a medium 

 temperature, and the dry residue treated repeatedly with petroleum 

 ether, which dissolves the benzoic acid, oxyacids, fat and phenol, 

 while the hippuric acid remains undissolved. This residue is now 

 dissolved in a little warm water and evaporated at 50-60 C. to 

 crystallization. The crystals are collected on a small weighed 

 filter. The mother-liquor is repeatedly shaken with acetic ether. 

 This last is removed and evaporated; the residue is added to the 

 above crystals on the filter, dried and weighed. 



Phenaceturic Acid, C,oH n N0 3 = C 6 H 5 .CH 2 .CO.NH.CH 2 .COOH. This 

 acid, which is produced in the animal body by a grouping of the phenyl- 

 acetic acid, C 6 H 5 .CH 2 .COOH, formed by the putrefaction of the proteids 

 with glycocoll, has been prepared from horse's urine by SALKOWSKI, but it 

 probably also occurs in human urine. 



Benzoic Acid, C 7 H 6 O 2 or C 8 H B .COOH, is found in rabbit's urine and some- 

 times, though in small amounts, in dog's urine (WEYL and y. ANBEP). Ac- 

 cording to JAARSVELD and STOKVIS and to KRONECKEK, it is also found in 

 human urine in diseases of the kidneys. The occurrence of benzoic acid in 



