202 SKATOXYL-SULPHUKIC ACID. 



When this substance is heated with zinc chloride it loses NH 3 

 and yields skatol 1 



:N T H 

 C 6 H/ CH. 



Since the condition of the occurrence and formation of skatol 

 are on the whole the same as those for indol, and since these sub- 

 stances further resemble each other in being both volatile and 

 hence passing over in the vapours arising from their heated solu- 

 tions, the method previously described for the preparation of indol 

 from putrefactive products may be applied for the preparation of 

 skatol. The separation of the two depends chiefly on the fact 

 that skatol is much less soluble in water than is indol, so that if 

 the mixed substances are dissolved in a minimal amount of ab- 

 solute alcohol, then on the addition of 8 10 volumes of water, 

 indol remains in solution while skatol is precipitated. 2 Skatol is 

 unaffected by being boiled with moderately strong caustic soda, 

 whereas indol is decomposed. This difference in behaviour to 

 caustic alkalis provides a further means by which the former 

 may be obtained free from the latter. 



Skatol is a crystalline substance which melts when heated to 

 93, and has a powerfully unpleasant odour, somewhat like that 

 of indol. 



Reactions. Many of the reactions of skatol resemble so closely 

 those of indol that they provide no means for distinguishing be- 

 tween the two substances. Skatol is however characterised by 

 yielding only a milky opacity instead of a red colouration on the 

 addition of fuming nitric acid to its aqueous solutions (see sub in- 

 dol), in not giving the reaction with a strip of pine-wood dipped 

 in hydrochloric acid which indol does, 3 by its lesser solubility in 

 water and greater resistance to the action of caustic soda. 



5. Skatoxyl-sulphuric acid. C 9 H 8 N . . S0 2 OH. 



The close relationship between indol and skatol is further 

 shown by the fact that the latter, like the former, after absorp- 

 tion from the alimentary canal is oxidised, the product being 

 skatoxyl C 9 H 8 N , OH, which unites, as does indoxyl, with the 

 elements of sulphuric acid and leaves the body in the urine as a 

 potassium salt of the above acid. 4 This salt may be isolated from 



1 E. Fischer, Ber. d. d. chem. Gesell. Bd. xix. (1886), S. 1563. Liebig's Ann. 

 Bd. ccxxxvi. (1886), S. 116. 



2 Brieger, Ber. d. d. chem. Gesell. Bd. xn. (1879), S. 1985. Zt. f. pkysiol. Chem 

 Bd.iv. (1880), S. 414. 



3 When, however, a strip of pine-wood is dipped into an alcoholic solution of 

 skatol and subsequently into strong hydrochloric acid, it is coloured first crimson, 

 which turns to bluish violet. Fischer, Liebig's Ann. Bd. ccxxxvi. (1886), S. 140. 



* Brieger, Zt. f. physiol. Chem. Bd. iv. (1880). S. 414. Baumann u. Brieger, 

 Ibid. Bd. in. (1879), S. 255. G. Hoppe-Seyler, Ibid. Bd. vii. (1883), S. 423. 



