PYROCATECHIN-SULPHURIC ACID. 727 



cresol into dibromcresol under exactly observed conditions is deter- 

 mined and from the quantities of bromine by weight (Bi and 62) 

 quantities by weight of phenol and cresol can be calculated. In regard to 

 the procedure as well as to the necessary solutions we refer to the original 

 publication. 



The methods for the separate determination of the conjugated sul- 

 phuric acid and the sulphate-sulphuric acid will be spoken of later in 

 connection with the determination of the sulphuric acid of the urine. 



Pyrocatechin-sulphuric Acid. This acid was first found in horse's urine in 

 rather large quantities by BAUMANN. It occurs in human urine only in the very 

 smallest amounts, and perhaps not constantly, but it is present abundantly in 

 the urine after taking phenol, pyrocatechin, or protocatechuic acid. 



With an exclusively meat diet this acid does not occur in the urine, and it 

 therefore must originate from vegetable food. It probably originates from the 

 protocatechuic acid, which, according to PREUSSE, passes in part into the urine 

 as pyrocatechin-sulphuric acid. This acid may also perhaps be formed by the 

 oxidation of phenol within the organism (BAUMANN and PREUSSE l ). 



Pyrocatechin, or O-DIOXYBENZENE, C 6 H 4 (OH)2, was first observed in the urine 

 of a child (EBSTEIN and J. MULLER). The reducing body ALCAPTON, first found 

 by BODEKER 2 in human urine and which was considered for a long time as iden- 

 tical with pyrocatechin, is in most cases probably homogentisic acid (see below). 



Pyrocatechin crystallizes in prisms which are soluble in alcohol, ether, and 

 water. It melts at 102-104 C., and sublimes in shining plates. The watery 

 solution becomes green, brown, and finally black in the presence of alkali 

 and the oxygen of the air. If very dilute ferric chloride is treated with tartaric 

 acid and then made alkaline with ammonia, and this added to a watery solution of 

 pyrocatechin, we obtain a violet or cherry-red liquid which becomes green on 

 adding excess of acetic acid. Pyrocatechin is precipitated by lead acetate. It 

 reduces an ammoniacal silver solution at the ordinary temperature, and with 

 heat reduces alkaline copper-oxide solutions but does not reduce bismuth oxide. 



A urine containing pyrocatechin, if exposed to the air, especially when alkaline, 

 quickly becomes dark and reduces alkaline copper solutions when heated. In 

 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 pyrocatechin 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, 3 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 pyrocatechin, it easily reduces 

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

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



1 Baumann and Herter, Zeitschr. f. physiol. Chem., 1; Preusse, ibid., 2; Baumann, 

 ibid., 3. 



2 Ebstein and Muller, Virchow's Arch., 62; Bodeker, Zeitschr. f. rat. Med. (3), 7. 

 J Lewin, Virchow's Arch., 92; Bass, Zeitschr. f. exp. Path. u. Ther., 10. 



