196 PYROCATECHIK 



acid, 1 C 7 H 7 O . S0 2 OH. The general conditions of its presence in 

 urine are practically identical with those for the occurrence of 

 phenylsulphuric acid. 2 When introduced into the animal body 

 the three isomeric kresols undergo distinctly different oxidational 

 changes. 3 



Reactions. On the addition of an excess of bromine water to 

 its solutions parakresol yields a brominated derivative, but the 

 compound is only obtained in a separate and crystalline form 

 after prolonged standing, differing characteristically from the 

 analogous compound of phenol, which under similar circumstances 

 is formed rapidly. It yields a reddish yellow colouration with 

 potassium nitroprusside and caustic potash, which turns bright 

 pink on the addition of an excess of acetic acid. 4 Aceton gives 

 a similar reaction. With furfurol and sulphuric acid the reaction 

 is closely similar to that which phenol gives. 5 



7. Pyrocatechin. C 6 H 4 (OH) 2 , Orthodioxybenzol. 



This substance occurs, in small amounts in human urine united 

 with sulphuric acid as a mono-ethereal compound OH . C 6 H 4 . O . 

 S0 2 OH. It is more plentifully present in the urine of herbivora, 

 especially of the horse, and is largely increased in amount by the 

 administration of benzol or phenol. 6 It is also stated to occur in 

 cerebrospinal fluid." When present in urine it (together with 

 hydrochinon) confers on this excretion, especially if alkaline, the 

 property of turning successively greenish, brown, and finally dark- 

 brown or almost black on exposure to the air, and of readily re- 

 ducing solutions of metallic salts, a fact to be taken into account 

 when dealing with the presence or absence of sugar in the urine. 

 Solutions of pyrocatechin turn emerald green on the addition of 

 a few drops of very dilute solution of ferric chloride, avoiding all 

 excess of the reagent. If the green solution is now acidulated 

 with tartaric acid, it turns violet on the subsequent addition of a 

 little ammonia and purplish-red on the addition of excess. The 

 green colour may be restored by excess of acetic acid. 8 It may 



1 Baumann, Ber. d. d. chem. Gesell. Bd. ix. (1876), S. 1389. Zt. f. ph>/siol. 

 Chem. Bd. 11. (1878), S. 335. Preusse; Ibid. S. 355. Brieger, Ibid. Bd. iv. 

 (1880), S. 204. 



2 Baumann u. Brieger; Ibid. Bd. in. (1879), S. 149. Baumann, Ibid. IT. S. 

 304. For the detection and separation of the kresols and phenol see Baumaun 

 u. Brieger, Ber. d. d. chem. Gesell. Bd. XH. (1879), S. 804. Baumann, Zt. f. 

 physiol. Chem. Bd. vi. (1882), S 183. Brieger, Ibid. Tin. (1883), S. 311. 



'3 Preusse, Ibid. Bd. T. (1881), S. 57. 

 * v. Jacksch, Zt.f. klin. Med. Bd. vm. (1884), S. 130. 



5 Udranszky, cit. (sub phenol). 



6 See Baumann, Pfl tiger's Arch. Bd. xn. (1876), S. 63, Baumann u. Herter, Zt. 

 f. physiol. Chem. Bd. I. (1877), S. 248, Baumann u. Preusse, Ibid. Bd. ill. (1879), S. 

 156. Brieger, Arch. f. phi/siol. Jahrg. 1879, Suppl.-Bd. S. 61. Nencki u. Giacosa, 

 Zt. f. physiol. Chem. Bd. 'IT. (1880), S. 325. Schmiedeberg, Arch. f. exp. Path. u. 

 Pharm. Bd. xiv. (1881), S. 288. 



7 Halliburton, Jl. of Physiol. Vol. x. (1889), p. 247. 



8 Ebstein u. Miiller, Yin-how's Arch. Bd. LXT. (1875), S. 394. See also Jacquemin, 

 Rev. Med. de PEst. T. TIII. (1877), p. 90. 



