CHAP. X.] IXDOL. 421 



INDOL, SKATOL AND SKATOL-CARBONIC ACID. 



/CH = CH 

 1. Indol, C 8 H 7 N, C 6 H 4 ( 



\NH 



Indol was first discovered by Baeyer in the products obtained by 

 distilling oxyindol with zinc-dust 1 . It was afterwards found by 

 Nencki 2 and by Kiihne 3 amongst the products of the putrefaction of 

 proteids, as well as in those obtained when the proteids are fused 

 with caustic alkalies. Indol, together with skatol (which almost 

 invariably accompanies it), is found in the contents of the large 

 intestine and in the faeces. 



Mode of pre- Two kg. of well-pressed fibrin are placed in a roomy 

 paration of in- flask (of the capacity of 12 litres), together with 8 litres 

 doi and skatol o f wa t er in which 2 grms. of KH.,P0 4 and 1 gr. of 

 ( rS) Skl ' S M S S 4 have been dissolved; to this fluid are added 

 200 c.c. of a saturated solution of Na 2 CO 3 and then 

 some cubic centimetres of a putrefying flesh infusion together with 

 fragments of decomposing meat. The flask is then closed with a 

 stopper, which has been bored and provided with a glass tube ; to 

 the latter is attached an indiarubber tube connected with a wash bottle 

 half filled with water. The indiarubber tube is provided with a 

 clamp, which is left open during the first days of the experiment. 

 The mixture is digested at a temperature of 40 42 C. for a period 

 of 5 or 6 days, the flask being shaken from time to time. As soon 

 as the evolution of gas has ceased, the clamp, above referred to, is 

 closed, and only opened from time to time to liberate the gases 

 which have accumulated. 



At the end of the time mentioned, the fluid contents of the flask 

 are distilled off, until the residue in the flask measures only 1 to 

 1*5 litres. The strongly ammoniacal distillate having been acidulated 

 with hydrochloric acid, which decomposes the sulphide of ammonium 

 present, is then precipitated with solution of sulphate of copper 

 and filtered. The clear filtrate is thoroughly shaken up, in repeated 

 fractions, with ether in a stoppered separating funnel of about half-litre 

 capacity. The united ethereal extracts are distilled until the residue 

 measures 500 cc., the residue is twice thoroughly shaken with 

 solution of caustic soda, with the object of separating phenol 

 and traces of acids. The ether is then distilled off at the lowest 

 possible temperature, and the oily residue having been treated 

 with caustic soda, is distilled in a current of steam, until no more 



1 Baeyer, Ann. Chem. u. Pharm. Vol. CXL. p. 295, and A. Emmerling and C. Engler, 

 .Ber. d. deutsch. chem. Gesellscli. Vol. i. p. 17, and Vol. in. p. 885. 



- M. Nencki, ' Ueber die Harnfarbstoffe aus der Indigogruppe und iiber die Pankreas- 

 verdauung.' Per. d. deutach. chem. Gesellsch. Vol. vm. (1875), p. 336. M. Nencki, 

 'Ueber das Indol,' ibid. Vol. vm. (1875), p. 722. 



3 Kuhne, Ber. d. deutsch. chem. Gesellsch. Vol. vm. (1875), p. 206 



