INFECTIONS OF THE DIGESTIVE TRACT 139 



A slight blue precipitate forms in solutions containing 

 one part of indol to 256,000 parts of water; in greater 

 dilution the coloration is green, and fails entirely when 

 the dilution is 1 : 1,024,000 parts. Even in this extreme 

 dilution chloroform will indicate the presence of the di- 

 indyl - di - hy dronaphthalme - keto - sodium - monosulpho- 

 nate by its faintly pink color. The reaction is essentially 

 a time reaction, and even in dilute solution it has been 

 found desirable to allow a period of not less than ten 

 minutes to elapse before shaking out the condensation 

 product with chloroform. The naphthaquinone solution 

 should be added in sufficient excess to tinge the filtrate 

 slightly yellow. 



As indol is sometimes associated in the course of putre- 

 faction with skatol (and this is not uncommonly so in 

 the case of the contents of the large intestine), it becomes 

 important to have a method for the separation of indol 

 and skatol. These putrefactive decomposition products 

 may be separated by means of their picrates, but the 

 method involves so much time as to make it unfit for 

 clinical or ordinary chemical investigations. It is 

 believed that the method described by Herter and 

 Foster l will prove useful in effecting the quick and nearly 

 complete separation of indol from skatol. Moreover, 

 this method serves also for the determination of the 

 quantity of skatol present. 



The procedure is based on the fact that by means of 

 the naphthaquinone method for indol which has just 



1 " On the Separation of Indol from Skatol and their Quanti- 

 tative Determination," Journ. Biol. Chem., II, p. 267, 1906. 



