THE AROMATIC CONSTITUENTS OF THE URINE. 269 



cording to the character of the aromatic component uniting with 

 glucuronic acid, the resulting compounds have been termed camphor- 

 glucuronic acid, urochloralic acid, menthol-glucuronic acid, phenyl- 

 indoxyl-, skatoxyl-glucuronic acid, etc. 



Of the origin of glucuronic acid little is known. That it is 

 formed in the tissues of the body is apparent from the fact that even 

 in a starving animal the administration of camphor, chloral, etc., 

 leads to elimination of these substances in combination with the acid 

 in question. As glucuronic acid is a derivative of glucose, we may 

 imagine that during starvation it is derived from glycogen, or even 

 from the albumins. It has been demonstrated, as a matter of fact, 

 that the formation of glycogen in the liver can be artificially in- 

 creased by introducing glucuronic acid with the food. The chemi- 

 cal relation of glucuronic acid to glucose has already been considered. 

 On oxidation glucose thus first yields the monobasic gluconic acid, 

 and then the dibasic saccharinic acid. The latter in turn may be 

 transformed into saccharo-lactonic acid, which on reduction yields 

 glucuronic acid, so that this stands midway between gluconic acid 

 and saccharinic acid. These relations are shown by the formulae : 



CH 2 .OH (CH.OH) 4 COH, glucose. 



CH 2 .OH (CH.OH) 4 COOH, gluconic acid. 



COOH - (CH.OH) 4 COH, glucuronic acid. 



COOH - (CH.OH) 4 COOH, saccharinic acid. 



On boiling with water glucuronic acid is, in part at least, trans- 

 formed into its anhydride, glucuron, C 6 H 8 O 6 . 



COH.CHOH.CH.CHOH.CHOH.CO 



Formerly glucuronic acid was also thought to be derived from 

 chondroitin-sulphuric acid ; this view, however, has now been aban- 

 doned. 



Glucuronic acid does not occur in crystalline form; it is a syrupy 

 substance which is readily soluble in water and alcohol. Its anhy- 

 dride, glucuron, however, is a crystalline body, and is likewise 

 soluble in water, but insoluble in alcohol. The free acid and its 

 alkaline salts are dextrorotatory, while the conjugate glucuronates 

 turn the polarized light to the left. The free acid, moreover, as 

 well as its salts and most of its compound ethers, reduce the oxides 

 of copper, bismuth, and silver in alkaline solution, and it is thus 

 possible to confound them with glucose if reliance is placed upon 

 the corresponding tests alone. With phenyl-hydraziii the free acid 

 is said to form a crystalline compound with a melting-point of 114- 

 115 C. Unlike glucose, it is non-fermentable. It gives the fur- 

 furol reaction and simulates the pentoses in reacting with phloro- 

 glucin hydrochlorate, but not with orcin (see Pentoses). The 

 amount of furfurol which may be obtained from glucuronic acid on 



