690 URINE. 



KOSSLER and PENNY'S Method with NEUBERG's 1 modification. The 

 liquid containing phenol is treated with N/ 10 caustic soda until strongly 

 alkaline, warmed on the water-bath in a flask with a glass stopper, and 

 then treated with an excess of N/10 iodine solution, the quantity being 

 exactly measured. Sodium iodide is first formed and then sodium 

 hypoiodite, which latter forms tri-iodophenol with the phenol accord- 

 ing to the following equation: 



C 6 H 5 OH + 3NaIO =C 6 H 2 I 3 .OH + 3NaOH. 



On cooling, acidify with sulphuric acid and determine the excess of iodine 

 by titration with N/10 sodium thiosulphate solution. This process is 

 also available for the estimation of paracresol. Each cubic centimeter 

 of the iodine solution used is equivalent to 1.5670 milligrams of phenol 

 or 1.8018 milligrams of cresol. As the determination does not give any 

 idea as to the variable proportions of the two phenols, the quantity of 

 iodine used must be calculated as one or the other of the two phenols. 

 Before such a determination is carried out, the concentrated urine is^ 

 first distilled after acidification with sulphuric acid and the distillate 

 purified by precipitation with lead, and distilled again (NEURERG). For 

 details, see NEUBERG, 1. c., and HOPPE-SEYLER-THIERFELDER'S Hand- 

 buch, 8. Aufl. 



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 2 ). 



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 3 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 ultimately black in the presence of alkali and 

 the oxgyen 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 acteate. 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 



1 Kossler and Penny, Zeitschr. f. physiol. Chem., 17; Neuberg, ibid., 27. 



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

 ibid., 3. 



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



