214 BACTERIAL ACTION IN THE INTESTINAL TRACT. 



The greater portion of the indol that is formed in the large in- 

 testine is no doubt eliminated in the feces. A certain amount, 

 however, is absorbed, and after oxidation to indoxyl appears in the 

 urine in combination with sulphuric acid as so-called indican (which 

 see). If larger quantities are formed, a variable fraction is further 

 eliminated in the urine as an indoxyl compound of glucuronic 

 acid. 



Indol crystallizes in small platelets, which melt at 52 C., and 

 are soluble in hot water, ether, alcohol, and benzol. Its odor is 

 feculent ; it is quite volatile, and when boiled with water passes over 

 into the distillate. With picric acid it forms a beautifully red crys- 

 talline compound, which is readily decomposed on boiling with 

 dilute ammonia ; the liberated indol is then found in the distillate. 

 On distilling in the presence of sodium hydrate, on the other hand, 

 the indol is decomposed. 



Tests. When treated in aqueous solution with nitric acid and a 

 trace of sodium nitrite a red precipitate of the nitrate of nitroso- 

 indol is formed. This is soluble in alcohol and crystallizes out upon 

 the addition of ether. 



If a small piece of pine wood is moistened with strong hydro- 

 chloric acid and then placed in a watery solution of indol, it gradu- 

 ally assumes a cherry-red color. 



An aqueous solution of indol is treated with a small amount of 

 a solution of sodium nitroprusside until a brownish-yellow color 

 develops. If now a dilute solution of sodium hydrate is added 

 drop by drop, the color changes to violet. Upon the further addi- 

 tion of a little dilute hydrochloric acid this becomes a deep blue, 

 while an excess of the acid destroys the blue color. 



On shaking a small quantity of an aqueous solution of indol 

 with a few drops of a 2 per cent, solution of dimethyl-p-amino- 

 benzaldehyde in equal parts of water and concentrated hydrochloric 

 acid, a cherry-red color develops either at once or upon the appli- 

 cation of heat. 



For the isolation of indol, see page 221. 



Skatol. Skatol, like indol, is a direct derivative of tryptophan, 

 and is likewise formed during the process of albuminous putrefac- 

 tion. It is a methylated indol, and may be represented by the 

 formula : 



/C (CH 3 )^ 

 C 6 H 4 \^ ^ '**. 



By combining with carbon dioxide it gives rise to the formation 

 of skatol-carbonic acid, which is also found in the contents of the 

 large intestine, and belongs to the ortho-series. Its formula is 



C 6 H 4 < >C.COOH. 



