PUTREFACTION PRODUCTS OF PROTE1DS. 169 



aqueous solution. The aromatic oxyacids may be obtained 

 by crystallizing from hot water the residue remaining after 

 evaporating the ether solution. 



To separate the two acids, the hydroparacumaric acid 

 and the paraoxyphenyl-acetic acid, their conduct towards 

 benzene may be utilized according to E. Baumann. Both 

 acids are difficultly soluble in benzene ; the hydroparacumaric 

 acid is, however, more readily soluble than the paraoxyphenyl- 

 acetic acid. A quantitative method of separation is not yet 

 known. 



PROPERTIES AND REACTIONS OF THE PRODUCTS OBTAINED. 

 i. Indol, C 6 H 4 <|>CH. 



Indol crystallizes from hot water in shining white leaf- 

 lets, and is easily volatile with steam. Melting-point 52. 

 It is difficultly soluble in water, readily soluble in ether, alco- 

 hol, benzene, and chloroform. If a solution of picric acid in 

 benzene be added to a solution of indol in petroleum ether, 

 shining red needles of a compound of equal molecules of indol 

 and. picric acid precipitate. These when distilled with 

 ammonia yield indol. Indol, when introduced into the 

 animal body, is oxidized to indoxyl and appears in the urine 



as potassium-indoxyl sulphate (indican), Q$r\rr 



REACTIONS OF INDOL. 



(a) If a cold saturated aqueous solution of indol be acidi- 

 fied with nitric acid and then a few drops of potassium nitrite 

 be added, a flocculent bright brick-red precipitate of nitroso- 

 indol nitrate, according to Nencki, C 16 H 13 (NO)N 2 .HN0 3 , is 

 formed. Very dilute solutions of indol only turn red; if 

 shaken with chloroform, a red-colored crust separates at the 

 surface of contact of the chloroform with the aqueous fluid. 



