A CTION OF EYTESTEVA L BA CTERIA ON P ROTE IDS. 469 
2. An aqueous solution of indol treated with fuming nitric acid turns a 
bright red colour, and on standing a red precipitate is formed. 
3. When sodium nitroprusside is added to a very dilute solution of indol, 
and afterwards caustic soda, the mixture turns a deep violet-blue, passing into 
a pure blue on making faintly acid with acetic acid, and disappearing with 
excess of acid (LegaFs reaction). 1 
/ XH \ 
Skatol? C f H 4 < / CH, is methyl-indol ; it crystallises in similar form 
X C.CH 3 ^ 
to indol (M. P., 95° C, B. P., 265° - 266 D C). It also possesses much the 
same solubilities as indol, and is volatile with steam. Passed through a red- 
hot tube, it decomposes and yields indol. 
It is distinguished, in addition to its physical properties, by the following 
tests : — 
1. Instead of a red precipitate, as in the case of indol, it gives a milky 
turbidity when treated with fuming nitric acid. 
2. In Legal's test (vide supra) it gives an intense yellow, turning violet 
with acid. 
3. It dissolves in concentrated hydrochloric acid, giving a highly coloured 
solution. 
Both indol and skatol, dissolved in benzol in concentrated solution, give, 
with a saturated solution of picric acid in benzol, a crop of fine red crystals. 
When the compound of indol and picric acid is treated with caustic soda, and 
distilled, the indol is decomposed ; under similar conditions the skatol picric 
acid compound yields skatol which is not decomposed. 
/ XH. 
Skatol carbonic acid? C,H/ >OCOOH, crystallises m scales (M. P., 
X C.CH 3 ^ 
164° C), sparingly soluble in water, easily soluble in alcohol and ether. Heated 
above its melting point, it breaks up into skatol and carbon-dioxide. 
It may be identified by the following tests : — 
1. Its aqueous solution, treated with pure nitric acid and afterwards with 
potassium nitrite solution, turns a cherry-red colour, and deposits a red pre- 
cipitate, which is dissolved by acetic ether. 
2. Its aqueous solution, treated with an equal volume of hydrochloric acid 
(sp. gr. 1*2), and afterwards with dilute bleaching powder solution, gradually 
turns a purple-red colour, and, after long standing, deposits a purple-red 
precipitate, easily soluble in alcohol. 
3. A very dilute solution (1 in 10,000 of water), treated with a few drops 
of hydrochloric acid, then with a few drops of a very dilute solution of ferric 
chloride, and heated, gives an intense violet colour. More concentrated solution 
gives an intense cherry-red colour. 
The aromatic compounds resulting from bacterial decomposition in the 
intestine are to a considerable extent absorbed. Tyrosine absorbed as such 
disappears ; it is decomposed and completely oxidised in the tissues without 
the formation of urea. The non-nitrogenous substances resulting from its de- 
composition by bacteria (as well as indol and skatol) are not completely 
oxidised, but are excreted in modified form in the urine, combined chiefly 
with sulphuric acid, as ethereal sulphates, but also in part with glycocoll and 
glycuronic acid. In this way the poisonous properties of the phenols and 
similar compounds are removed, for the ethereal sulphates formed are very 
1 Breslau. iirztl. Ztschr., 1893. 
3 Brieger, Ber. d. deutsch. chem. GeseUsch., Berlin, 1877, Bd. x. S. 1028. 
3 E. and H. Salkowski, Ztschr. f. physio?. Chem., Strassbnrg, 1885, Bd. ix. S. 8. 
