222 THE CARBOHYDRATES. 



PILOTY 1 by the reduction of the lactone of saccharic acid. On oxidation 

 with bromine it forms saccharic acid, and on reduction it yields gulonic- 

 acid lactone. SALKOWSKI and NEUBERG 2 have obtained Z-xylose from 

 glucuronic acid by splitting oft CCb by means of putrefaction bacteria. 



Glucuronic acid has not been found in the free state in the animal 

 body. It occurs to a slight extent in normal urine as a conjugated acid 

 (MAYER and NEUBERG). It occurs to a much greater extent in urine as 

 conjugated acid after the ingestion of certain aromatic and also aliphatic 

 substances, especially camphor and chloral hydrate. It was obtained 

 first by SCHMIEDEBERG and MEYER from camphoglucuronic acid, and 

 then by v. MERING 3 from urochloralic acid by cleavage with dilute acids. 

 According to P. MAYER, 4 on the oxidation of glucose a partial forma- 

 tion of glucuronic acid and oxalic acid takes place, and therefore, according 

 to him, an increased elimination of conjugated glucuronic acids shows 

 in certain cases an incomplete oxidation of glucose. Conjugated glucu- 

 ronic acids may also occur in the blood (P. MAYER, LEPINE and BOULUD 5 ), 

 in the feces, and in the bile. 6 NEUBERG and NEIMANN 7 have prepared 

 certain conjugated glucuronic acids (see Chapter XIV) synthetically, 

 among them being euxanthic acid. The most abundant source of glucu- 

 ronic acid is the artist's pigment " Jaune indien," which contains the 

 magnesium salt of euxanthic acid (euxanthon-glucuronic acid). 



Glucuronic acid is not crystalline, but is only obtainable as a syrup. 

 It dissolves in alcohol and is readily soluble in water. If the aqueous 

 solution is boiled for an hour the acid is partly (20 per cent) converted 

 into the crystalline lactone, glucurone, CoHsOe, which is soluble in water 

 and insoluble in alcohol, and which has a melting-point of 175-178 C. 

 The alkali salts of the acid are crystalline. If a concentrated solution 

 of the acid is saturated with barium hydroxide the basic barium salt is 

 obtained as a precipitate. The neutral lead salt is soluble in water, 

 while the basic salt is insoluble. The readily crystallizable cinchonine 

 salt can be used in isolating glucuronic acid (NEUBERG 8 ) . Glucuronic 

 acid is dextrorotatory, while the conjugated acids are levorotatory; 

 they behave like glucose with the reduction tests, and do not ferment 



1 Ber. d. d. chem. Gesellsch., 24. 



2 Zeitschr. f. physiol. Chem., 36. 



8 Mayer and Neuberg, Zeitschr. f. physiol. Chem., 29; Schmiedeberg u. Meyer, 

 ibid.,&; v. Mering, ibid, 6. 



4 Zeitschr. f. klin. Med., 47. See Chapter XIV. 



6 Mayer, Zeitschr. f. physiol. Chem., 32; L4pine and Boulud, Compt. rend.., 133, 

 134, 138. 



See Bial, Hofmeister's Beitrage, 2, and v. Leersum, ibid., 3. 



7 Zeitschr. f. physiol. Chem., 44. 



8 Ber. d. d. chem. Gesellsch., 33. 



