DISACCHARIDES. 223 



with yeast. With the phenylhydrazine test it gives crystalline com- 

 pounds which are not sufficiently characteristic (THIERFELDER, P. 

 MAYER 1 ). By the action of 3 mol. phenylhydrazine and the necessary 

 amount of acetic acid upon 1 mol. glucuronic acid at 40 for a few days, 

 NEUBERG and NEIMANN obtained the glucuronic-acid osazone, which 

 was very similar to glucosazone and melted at 200-205. With p-brom- 

 phenylhydrazine hydrochloride and sodium acetate, glucuronic acid gives 

 p-bromphenylhydrazine glucuronate, which is characterized by its insolu- 

 bility in absolute alcohol and by a very prominent levorotatory action. 

 This compound is very well suited for the detection of glucuronic acid. 2 

 Dissolved in a mixture of alcohol and pyridine (0.2 gram substance in 4 cc. 

 pyridine and 6 cc. alcohol) the rotation is 7 25', which corresponds to 

 ()= 369. On distillation with hydrochloric acid, glucuronic acid 

 yields furfurol and also carbon dioxide, and on this behavior TOLLENS 

 and LEFEVRE 3 have based their quantitative method for the estimation 

 of glucuronic acid. 



They give the pentose reactions with phloroglucin or orcin and hydrochloric 

 acid, and also a good reaction with naphthoresorcinol and hydrochloric acid 

 (see page 218). The product produced herewith is soluble in ether with a blue, 

 bluish-violet or reddish-violet color, and the solution shows an absorption band 

 somewhat to the right and on the D-line. According to MANDEL and NEUBERG 4 

 this reaction is not characteristic of glucuronic acid, as many aldehyde and ketone 

 acids give the same reaction; still, it is important in the differentiation of the 

 pentoses. 



Glucuronic acid is best prepared from euxanthic acid, which decom- 

 poses on heating it with water to 120 C. for several hours. The nitrate 

 from the euxanthon is concentrated at 40 C., when the anhydride 

 gradually crystallizes out. On boiling the mother-liquor for some time 

 and evaporating further, the crystals of the lactone are obtained. In 

 regard to the quantitative estimation of glucuronic acid we must refer 

 the reader to the works of TOLLENS and his collaborators and of NEUBERG 

 and NEIMANN. 5 



2. Disaccharides. 



Some of the varieties of sugar belonging to this group occur ready 

 formed in nature. Thus we have saccharose and lactose. Some, on the 

 contrary, such as maltose and isomaltose, are produced by the partial 



1 Thierfelder, Zeitschr. f. physiol. Chem., 11, 13, 15; P. Mayer, ibid,, -29. 



2 See Netiberg, Ber d. d. chem. Gesellsch., 32; and Mayer and Neuberg, Zeitschr. 

 f. physiol. Chem., 29. 



3 Ber. d. d. chem. Gesellsch., 40. 



4 Bioch. Zeitschr. 13. 



5 Tollens, Zeitschr. f. physiol. Chem., 44, which cites also the older work; Neuberg 

 and Neimann, ibid., 44; Neuberg, ibid., 45. 



