SKATOL. 199 



matter of fact, that under the influence of certain organisms, such 

 as the Proteus vulgaris, indol is formed almost exclusively. 



Structurally indol is closely related to indigo, and according to 

 Nencki this transformation can be effected through the action of 

 ozone. It is represented by the equation : 



/CH X \ /C<K / C O\ 



2C < NH > H + 4 " C '<NH/ C = C <NH/ 6H ' + 2H - 

 Indol. Indigo. 



Conversely, indigo can be transformed into indol on reduction. 



From the albumins the substance can also be obtained on fusion 

 with potassium hydroxide (see page 38). 



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 

 (pages 90 and 250). 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, however, on boil- 

 ing with dilute ammonia, and 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. 



For the isolation of indol, see page 206). 



Skatol. Skatol, like indol, belongs to the ortho-series, and is 

 likewise formed during the process of albuminous putrefaction. It 

 is a methylated indol, and may be represented by the formula : 



C 6 H 4 < 



NH 



By combining with carbon dioxide it gives rise to the formation 



