156 THE PROTEIN SUBSTANCES. 



acid a red liquid and then a red precipitate of nitroso-indol nitrate 

 (NENCKi 1 ). It is better first to add two or three drops of nitric acid 

 and then a 2-per cent solution of potassium nitrite, drop by drop (SAL- 

 KowsKi 2 ). Skatol does not give this reaction. An alcoholic solution 

 of indol treated with hydrochloric acid colors a pine chip cherry -red. 

 Skatol does not give this reaction. Indol gives a deep reddish-violet 

 color with sodium nitroprusside and alkali (LEGAL'S reaction). On 

 acidifying with hydrochloric acid or acetic acid the color becomes pure 

 blue. Skatol does not act the same. The alkaline solution is yellow 

 and becomes violet on acidifying with acetic acid and boiling. With a 

 few drops of a 4-per cent formaline solution and concentrated sulphuric 

 acid indol gives a beautiful violet color while skatol gives a yellow or 

 brown color (KoNDO 3 ) . Skatol dissolves in concentrated hydrochloric 

 acid with a violet coloration. On warming skatol with sulphuric acid 

 a beautiful purple-red coloration is obtained (CIAMICIAN and MAGNANINI 4 ) . 



For the detection of indol and skatol in, and their preparation from, 

 feces and putrefying mixtures, the main points of the usual method are 

 as follows: The mixture is distilled after acidifying with acetic acid; 

 the distillate is then treated with alkali (to combine with any phenols 

 which may be present) and again distilled. From this second distillate 

 the two bodies, after the addition of hydrochloric acid, are precipitated 

 by picric acid. The precipitated picrate is then distilled with ammonia. 

 The two bodies are obtained from the distillate by repeated shaking with 

 ether and evaporation of the several ethereal extracts. The residue, 

 containing indol and skatol, is dissolved in a very small quantity of abso- 

 lute alcohol and treated with 8-10 vols. of water. Skatol is precipitated, 

 but not the indol. The further treatment necessary for their separation 

 and purification will be found in other works. 5 



Skatosine, Ci H 16 N 2 O 2 , is a base first obtained by BAUMmthe pancreas auto- 

 digestion and later studied by SWAIN. It develops an indol- or skatol-like odor 

 on fusing with potassium hydroxide. LANGSTEIN 6 obtained a substance which is 

 perhaps identical with skatosine, in the very lengthy peptic digestion of blood 

 proteins. 



1 Ber. d. d. deutsch. chem. Gesellsch., 8, 727, and ibid., 722 and 1517. 



2 Zeitschr. f. physiol. Chem., 8, 447. In regard to newer reactions for indol and 

 skatol, see Steensma, ibid., 47, and Deniges, Compt. rend. soc. biol., 64. 



3 Zeitschr. f. physiol. Chem., 48; see also Dakin, Journ. of biol. Chem., 2. 



4 Ber. d. d. chem. Gesellsch., 21, 1928. 



5 For quantitative, colorimetric determinations of indol in feces see Einhorn and 

 Hiibner, Salkowski's Festschrift, Berlin, 1904; C. A. Herter and Foster, Journ. of 

 biol. Chem., 2. 



8 Baum, Hofmeister's Beitrage, 3; Swain, ibid.; Langstein, see Hofmeister, Ueber 

 Bau und Gruppierung der Eiweisskorper, in Ergebnisse der Physiologic, I, Abt. 1, 

 1902. 



