200 BACTERIAL ACTION IN THE INTESTINAL TRACT. 



ofskatol-r(irb<>nicacid,wlrid\ is also found in the contents of the 

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



/C(CH,U 

 C 6 H 4 ">C.COOH. 



Like indol, skatol is also formed on fusing albumins with caustic 

 soda, and can be obtained from indigo on reduction with tin and 

 hydrochloric acid. When passed through a red-hot tube it yields 

 indol. On absorption, it is oxidized to skatoxyl and is eliminated in 

 the urine in combination with sulphuric acid and glucuronic acid, as 

 in the case of indol (see pages 90 and 250). Skatol-carbonic acid, on 

 the other hand, appears in the urine as such. 



Skatol crystallizes in fine platelets, which melt at 95 C. and are 

 readily soluble in ether, alcohol, and benzol ; in hot water it is 

 soluble with greater difficulty than indol. Its odor is exceedingly 

 offensive. Like indol, it is volatile, and combines with picric acid 

 to form a red crystalline compound. On distilling this in ammo- 

 niacal solution or in the presence of sodium hydrate the skatol passes 

 over as such, while indol in the latter instance is decomposed. On 

 distilling a mixture of indol and skatol in aqueous solution the 

 skatol passes over first, and it is thus possible to separate the two 

 substances from each other. 



Tests. From its aqueous solutions skatol is precipitated by yellow 

 nitric acid as a white substance skatol nitrate. 



If a small piece of pine wood is moistened with an alcoholic solu- 

 tion of skatol and then placed in strong hydrochloric acid, it assumes 

 a red color. If, on the other hand, the test is conducted as with 

 indol, no reaction is obtained. 



With nitric acid of a specific gravity of 1.2 skatol gives a marked 

 xanthoproteic reaction on boiling i.e., a yellow color which changes 

 to orange when ammonia is added in excess. 



The substance does not give the reaction with sodium nitro- 

 prusside. 



Isolation (see page 206). 



Phenol. The phenol which is formed during the process of 

 intestinal putrefaction is derived from tyrosin. As has been shown, 

 this is first reduced to hydroparacumaric acid. This in turn is 

 oxidized to para-oxy-phenyl-acetic acid. Paracresol then is formed 

 through a splitting off of carbon dioxide, and on subsequent oxida- 

 tion phenol results (see page 96). To a certain extent this is elimi- 

 nated in the feces, but a variable amount is always absorbed, and 

 subsequently oxidized in part to hydroquinon or pyrocatechin. 

 These three bodies then combine with sulphuric acid and {ire elimi- 

 nated through the urine in this form. A certain amount of para- 

 cresol, moreover, is absorbed as such, and likewise appears in the 

 urine as a conjugate sulphate. According to some observers, indeed, 

 a larger quantity of paracresol is here encountered than of phenol. 



