INDOL AND SKATOL. 155 



with hydrochloric acid and washed with water is introduced into a 

 concentrated tryptophane solution, it becomes purple (pyrrole reaction) 

 On drying. The melting-points of the benzoylsulphotryptophane, the 

 /?-naphthalenesulphotryptophane and the naphthylisocyanatetrypto- 

 phane are according to ELLINGER and FLAMAND/ 185, 180 and 158 

 C. respectively. Several compounds of tryptophane have been prepared 

 by ABDERHALDEN and KEMPE. 2 Among these we will mention the trypto- 

 phane chloride hydrochloride, because it is used as the starting material 

 for the synthesis of tryptophane polypep tides. 



In regard to the rather complicated method for preparing trypto- 

 phane we must refer to the original work of HOPKINS and COLE, of NEU- 

 BERG, and of ABDERHALDEN and KEMPE. S 



As shown by HOPKINS and CoLE, 4 tryptophane on anaerobic putre- 

 faction yields indolpropionic acid and indolacetic acid, and indol and 

 skatol on aerobic putrefaction. Among these putrefactive products the 

 indol and skatol will be specially discussed. 



CH 



Indol, C 8 H 7 N = C 6 H 4 <^\CH, and Skatol, or /?-METHYLINDOL, 



NH 

 C.CH 3 

 C 9 H 9 N-C 6 H 4< /V CH ^ are formed - m variable quantities from pro- 



NH 



tein compounds under different conditions. Hence they occur habitually 

 in the human intestinal canal, and, after oxidation into indoxyl and 

 skatoxyl respectively, pass, at least partly, into the urine as the cor- 

 responding ethereal sulphuric acids and also as glucuronic acids. 



Indol and skatol crystallize in shining leaves, and their melting- 

 points are 52 and 95 C. respectively. Indol has a peculiar excremen- 

 titious odor, while skatol has an intense fetid odor (skatol obtained from 

 indigo is odorless). Both bodies are easily volatilized by steam, skatol 

 more easily than indol. They may both be removed from the watery 

 distillate by ether. Skatol is the more insoluble of the two in boiling 

 water. Both are easily soluble in alcohol and give with picric acid a 

 compound crystallizing in red needles. If a mixture of the two picrates 

 be distilled with ammonia, they both pass over without .decomposition: 

 while if. they are distilled with caustic soda, the indol but not the skatol 

 is decomposed. The watery solution of indol gives with fuming nitric 



2 Zeitschr. f. physiol. Chem., 52, and Ber. d. d. chem. Gesellsch., 40. 



3 Hopkins and Cole, Journ. of Physiol., 27 and 29; Neuberg and Popowsky, Biochem. 

 Zeitschr., 2; Abderhalden and Kempe, Zeitschr. f. physiol. Chem., 52. 



4 Journ. of Physiol., 29. 



