HIPPURIC ACID. 719 



cipitation of allantoin from the urine can be accomplished by mercuric 

 nitrate and by mercuric acetate solutions, in the presence of sodium 

 acetate. 



Glyoxylic Acid, C 2 H 4 4 , QQQTT , is produced on boiling allantoin as well as 



uric acid with alkalies, and also on the oxidation of many substances, among 

 which we can mention creatine and creatinine. It is also of interest that allantoin 

 can be prepared synthetically from glyoxylic acid and urea and that glyoxylic 

 acid yields oxalic acid when introduced into the body. The reports in regard 

 to its occurrence in the urine conflict, 1 as it is readily destroyed in the body, and 

 its passage into the urine is very improbable, or at least only seldom occurs. 



Hippuric Acid (BENZOYL-AMINO ACETIC ACID), 



C 9 H 9 NO 3 = (C 6 H 5 CO)HN CH 2 COOH. 



This acid decomposes into benzoic acid and glycocoll on boiling with 

 mineral acids or alkalies, and also in the putrefaction of the urine. The 

 reverse of this occurs if these two components are heated in a sealed 

 tube, according to the following equation: C 6 H 5 COOH+NH2.CH2.COOH 

 = C 6 H5.CO.NH.CH2.COOH+H 2 O. This acid may be synthetically 

 prepared from benzamide and monochloracetic acid, CeH5.CO.NH2 

 +CH 2 Cl.COOH = C 6 H 5 .CO.NH.CH 2 .COOH-r-HCl, and in various other 

 ways, but most simply from glycocoll and benzoyl chloride in the presence 

 of alkali. 



Hippuric acid occurs in large amounts in the urine of herbivora, 

 but only in small quantities in that of carnivora. The quantity of hip- 

 puric acid eliminated in human urine on a mixed diet is usually less than 

 1 gram per day; as an average it is 0.7 gram. After eating freely of vege- 

 tables and fruit, especially such fruit as plums, the quantity may be 

 more than 2 grams. Hippuric acid is also found in the perspiration, the 

 blood, the suprarenal capsule of oxen, and in ichthyosis scales. Noth- 

 ing is positively known in regard to the quantity of hippuric acid in the 

 urine in disease. 



The Formation of Hippuric Acid in the Organism. Benzoic acid and 

 also the substituted benzoic acids are converted into hippuric acid and 

 substituted hippuric acids within the body. Moreover, those bodies 

 are transformed into hippuric acid which by oxidation (toluene, cinnamic 

 acid, hydrocinnamic acid) or by reduction (quinic acid) are converted 

 into benzoic acid. The question of the origin of hippuric acid is there- 

 fore connected with the question of the origin of benzoic acid; the for- 

 mation of the second component, glycocoll, from the protein substances 

 in the body is unquestionable. 



1 The literature on the occurrence and detection of glyoxylic acid in the urine can 

 be found in Granstrom, Hofmeister's Beitrage, 11. 



