196 KRESOL. 



urine its detection necessitates the decomposition of its compound 

 viz. the phenylsulphate of potassium. This is best brought about 

 by distilling the urine (200 c.c.) with strong hydrochloric acid (40 c.c.) 

 or 5 p.c. of sulphuric acid until about 150 c.c. of distillate has passed 

 over. The distillate contains free phenol which is tested for qualita- 

 tively by the reactions described below and estimated quantitatively 

 by the formation of a compound with bromine, tribrornphenol, 

 C 6 H 2 Br 3 .OH. ] 



Phenol reactions (i), A violet-blue colouration on the addition of 

 neutral solutions of perchloride of iron. This colour is similar to that 

 yielded by salicylic acid but the absorption spectra of the two are 

 stated to be different 2 . It is destroyed by excess of the reagent and 

 is also not obtained in presence of acids and alkalis or of alcohol 3 , 

 (ii) When a solution of phenol is mixed with one quarter of its bulk 

 of ammonia and a few drops of chloride of lime solution (1 to 20 of 

 water) and gently warmed it yields a blue colouration 4 , (iii) When 

 boiled with Millon's reagent a marked and persistent pink or red colour 

 similar to that yielded by tyrosin is obtained 5 , (iv) Mere traces of 

 phenol give a yellowish crystalline precipitate on the addition of 

 bromine water. This reaction is used as stated above for the quanti- 

 tative estimation of phenol. Of these reactions (iii) and (iv) are the 

 most delicate, (v) On the addition of furfurol (C 5 H 4 O 2 , aldehyde of 

 pyromucic acid) solution (*5 p.c.) and strong sulphuric acid, phenol 

 yields a brilliant red colour which finally turns to blue 6 . 



6. Kresol. C 6 H 4 . OH . CH 3 . Methylphenol. 



This homologue of phenol exists in three isomeric forms, ortho-, 

 para- and metakresol. It is now known that the phenols which 

 may be obtained by the distillation of urine with acids consist 

 preponderatingly of parakresol, accompanied in some cases by ortho- 

 kresol and possibly (?) by metakresol in minute amounts. Like 

 phenol it is not found free in urine but as kresylsulphuric acid 7 , 

 C 7 H 7 O . SO 2 OH. The general conditions of its presence in urine are 

 practically identical with those for the occurrence of phenylsulphuric 



1 Landolt, Ber. d. d. chem. Gesell. 1871, S. 770. 



2 Krukenberg, Verhandl. d. physik-med. Gesell. zu Wurzburg, Bd. xvni. (1884), 

 S. 197. 



3 Hesse, Liebig's Annal. Bd. 182, (1876), S. 161. 



4 E. Salkowski, Pfliiger's Arch. Bd. v. (1872), S. 353. 



5 Plugge, Zt.f. anal. Chem. Bd. xi. (1872), S. 173. See also Alm&i, Ibid., Bd. 

 xvn. (1878), S. 107. 



6 Udranszky, Zt. f. physiol. Chem. Bd. xn. (1888), Sn. 355, 377. 



7 Baumann, Ber. d. d. chem. Gesell. Bd. ix. (1876), S. 1389. Zt. f. physiol 

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

 (1880), S. 204. 



