DETECTION OF GLYCURONIC ACID 325 



chloric acid, into a coloring matter which gives a blue color 

 in ether, and in solution gives a dark spectral band in the 

 vicinity of the sodium lime. It is true that this reaction is 

 also not specific for glycuronic acid ; it occurs also (as shown 

 by A. Mandel and C. Neuberg) 62 with many aliphatic 



CO 



aldehyde- and ketonic-acids containing the group I 



beginning with glyoxylic acid, | , and seems to be due 



to a certain combination between carboxyl and carbonyl 

 groups. Indoxyl may also cause confusion. 63 The test is 

 suited, however, for positive differentiation of glycuronic 

 acid from the pentoses. If glycuronic acid in a mixture of 

 different sugars is precipitated with these as an osazone, the 

 glycuronic acid osazone alone will give the Tollens color 

 reaction. 64 



A very valuable recent reaction for glycuronic acid has 

 been originated by Guido Goldschmiedt, as above stated; he 

 found that glycuronic acid with a-naphthol and concentrated 

 sulphuric acid will give an emerald green color (passing into 

 violet and blue when diluted with water) . Neither hexoses 

 nor pentoses give this reaction, which is directly applicable 

 in human urine only when the diet is free from nitrates (as 

 milk, white bread and meat) . The urine of dogs and rabbits 

 is always free from nitrites, as proved by the diphenylamine 

 reaction. 65 



A method of quantitative determination of glycuronic 

 acid has been recently proposed by Lefevre and Tollens. It 

 depends on the fact that if urine is precipitated by acetate 

 of lead and ammonia, the furfurol appearing in distillation 



" A. Mandel and C. Neuberg, Biochem. Zeitschr., 13, 148, 1908; C. Neuberg, 

 ibid., 2Jt, 436, 1910. 



**R. Bernier, Jour. d. Pharm. et de Chim., series 7, 2, 401, 1910; cited in 

 Jahresber. f. Tierchem., 40, 301, 1910. 



84 C. Neuberg, and S. Saneyoshi, Biochem. Zeitschr., 36, 56, 1911. 



"G. Goldschmiedt (Prague), Zeitschr. f. physiol. Chem., 65, 389, 1910; 

 67, 194, 1910; cf. also L. v. Udransky, ibid., 68, 88, 1910. 



