THE URINE. 365 



weighed filter, washed with dilute bromine-water, dried over sul- 

 phuric acid without the use of a vacuum and weighed (331 parts 

 tribromphenol correspond to 94 parts phenol). Paracresol is gradu- 

 ally converted into tribromphenol by this treatment with bromine- 

 water. The methods for the separate determination of the coupled 

 sulphuric 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 (and PYROCATECHIN). This acid was first 

 found in horses' urine iii rather large quantities by BAUMANN. It only occurs 

 in human urine in the very smallest quantities and perhaps not constantly, 

 but it occurs abundantly in the urine after taking phenol, pyrocatechin, or 

 protocatechinic acid. 



On an exclusive meat diet this acid does not occur in the urine, and it 

 therefore originates from the 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 depend on 

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



Pyrocatechin, or o-DioxYBENZOL, C 6 H4(OH) a , was first observed in the 

 urine of a child (EPSTEIN and J. MULLER). The reducible body ALCAPTON, 

 first found by BODEKER in human urine and which was considered for a long 

 time as identical with pyrocatechin, is UROLEUCIC ACID, according to KIRK. 



Pyrocatechiu crystallizes in prisms which are soluble in alcohol, ether, 

 and water. It melts at 102-104 0. and sublimes in shining plates. The 

 watery solution becomes green, brown, and ultimately 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 by saturating with acetic acid. Pyrocatechin is precipitated 

 by lead acetate. It reduces an ammoniacal silver solution at the ordinary 

 temperature and reduces alkaline copper-oxide solutions with heat, 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 with 

 heat. 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 benzol. 



Hydroctonon, or P-DIOXYBENZOL, CeH^OEDa, often occurs in the urine 

 after the use of phenol (BAUMANN and PREUSSE). The dark color which cer- 

 tain urines, so-called " carbolic urines," take in the air is due to decomposition 

 products. Hydrochinon does not occur as a normal constituent of urine, but 

 after the administration of hydrochinon ; according to v. MERINO and LEWIN, 

 it passes into the urine of rabbits as ethereal sulphuric acid, as a decomposition 

 product of arbutin. 



Hydrochinon forms rhombical 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 

 with lead acetate. It is oxidized into chinon by ferric chloride and other 

 oxidizing agents, and chinon is detected by its peculiar odor. Hydrochinon- 

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

 sulphuric acid. 



