CHAP. X.] 



SKATOL-CARBONIC ACID. 



427 



Reactions. 



complicated that the reader is referred, for the description, to Salkowski's 

 original paper. The body possesses, however, chemical characters 

 which permit of its ready identification, and the following method 

 suffices to yield a product which enables its reactions to be tried. 



Thirty or fifty cc. of the decomposing liquid are concentrated, on 

 the water bath, to about one-fifth their volume, by which means indol 

 and skatol are driven off. The liquid is then acidified with glacial 

 acetic acid and shaken with ether. The ether is separated and 

 shaken with a very weak solution of sodium carbonate, which takes 

 up the acid from the ethereal solution. The sodium skatol-carbonate 

 solution can then be employed for trying the reactions. 



Properties of Skatol-carbonic acid occurs in the form of colourless 

 skatoi-carbonic i ea fl ets which are readily soluble in alcohol and ether, 

 and sparingly soluble in water. They melt at a tem- 

 perature of 164 C. When still further heated, the body splits up 

 into skatol and carbon dioxide. 



1. (Nitric acid and potassium nitrite 1 .} When a 

 solution of the acid (which may only contain 1 part in 

 1000 of water) is treated with some drops of pure nitric acid (of 

 sp. gr. 1*2) and then with a few drops of potassium nitrite solution 

 (2 %), the solution assumes pretty generally a cherry-red colour ; it 

 then becomes turbid and deposits a red colouring matter, which is 

 dissolved by acetic ether, when this liquid is shaken up with it. The 

 solution in acetic ether exhibits, if sufficiently diluted, an absorption 

 band in the green. When the solution in acetic ether is shaken up 

 with solution of caustic soda, the former is decolourised, whilst the 

 former acquires an intense yellow colour. If now an excess of 

 hydrochloric acid be added the red colour is restored, and again is 

 dissolved by acetic ether. Instead of acetic ether, amyl-alcohol may 

 be employed, in which the red colouring matter is even more soluble. 

 It is insoluble in ether, benzol, and chloroform. The reaction with 

 nitric and nitrous acids, though reminding one of the indol reaction 

 can be shewn not to depend on the formation of nitrate of nitroso- 

 indol (Salkowski). 



2. (Hydrochloric acid and bleaching powder 2 .) 



The aqueous solution is treated with an equal volume of HC1 

 (of 1-2 sp. gr.) and, afterwards, with some drops of a weak (1 2 %) 

 solution of bleaching powder. The mixture gradually acquires a 

 purple-red colour and, after long standing, deposits a purple-red 

 precipitate which is easily soluble in alcohol. 



3. (Hydrochloric acid and ferric chloride 2 .) 



This reaction is much more delicate than the two first. If, to a 

 solution containing 1 part of the acid in 10,000 of water, a few drops 



1 Salkowski, 'Ueber das Verhalten der Skatolcarbonsaure im Organismus, ' Zeitsch. 

 f.phys. Chem. Vol. ix. (1885), p. 23. 



2 Salkowski, op. cit. Zeitsch. f. phys. Chem. Vol. ix. p. 25. 



