INDOXYL-SULPHURIC ACID. 691 



detecting pyrocatechin in the urine it is concentrated when necessary, filtered, 

 boiled with the addition of sulphuric acid to remove the phenols, and repeatedly 

 shaken, after cooling, with ether. The ether is distilled from the several ethereal 

 extracts, the residue neutralized with barium carbonate and shaken again with 

 ether. The pyroeatechin which remains after evaporating the ether may be 

 purified by recrystallization from benzene. 



Hydroquinone, or p-DioxYBENZENE, C 6 H 4 (OH) 2 , often occurs in the urine after 

 the use of phenol (BAUMANN and PREUSSE). The dark color which certain urines, 

 so-called " carbolic urines," assume in the air is due to decomposition products. 

 Hydroquinone does not occur as a normal constituent of urine, but only after 

 the administration of hydroquinone ; and according to LEWiN, 1 it may be found 

 in the urine of rabbits as an ethereal-sulphuric acid, being a decomposition product 

 of arbutin. 



Hydroquinone forms rhombic crystals which are readily soluble in water, 

 alcohol, and ether. It melts at 169 C. Like pyroeatechin, it easily reduces 

 metallic oxides. It acts like pyroeatechin with alkalies, but is not precipitated 

 by lead acetate. It is oxidized into quinone by ferric chloride and other oxidiz- 

 ing agents, and quinone can be detected by its peculiar odor. Hydroquinone- 

 sulphuric acid is detected in the urine by the same methods as pyrocatechin- 

 sulphuric acid. 



C.O.SO 2 .OH 

 Indoxyl-sulphuric Acid, C 8 H 7 NS0 4 , C 6 H 4 /\CH , also called 



NH 



URINE INDICAN, formerly called UROXANTHINE (HELLER), occurs as an 

 alkali-salt in the urine. This acid is the mother-substance of a great 

 part of the indigo of the urine. The quantity of indigo which can be 

 separated from the urine is considered as a measure of the quantity of 

 indoxyl-sulphuric acid (and indoxyl-glucuronic acid) contained in the 

 urine. This amount, according to JAFFE, 2 for man is 5-20 milligrams per 

 twenty-four hours. Horse's urine contains about twenty-five times as 

 much indigo-forming substance as human urine. 



Indoxyl-sulphuric acid is derived, as previously mentioned (page 492), 

 from indol, which is first oxidized in the body into indoxyl and is then 

 conjugated with sulphuric acid. After subcutaneous injection of indol 

 the elimination of indican is considerably increased (JAFFE, BAUMANN 

 and BRIEGER, and others). It is also increased by the introduction 

 in the animal organism of orthonitrophenolpropiolic acid (G. HOPPE- 

 SEYLER 3 ) . Indol is formed by the putrefaction of proteins. The 

 putrefaction of secretions rich in protein in the intestine also explains the 

 occurrence of indican in the urine during starvation. Gelatin, on the 

 contrary, does not increase the elimination of indican.. 



An abnormally increased elimination of indican occurs in those 



1 Virchow's Arch., 92. 



2 Pfliiger's Arch., 3. 



3 Jaffe, Centralbl. f. d. med. Wissensch., 1872; Baumann and Brieger, Zeitschr. f. 

 physiol. Chem., 3; G. Hoppe-Seyler, ibid., 7 and 8. See also Porcher and Hervieux, 

 Journ. de Physiol., 7. 



