INDOLE  , or BENioPYRR0I., CBH,N, a substance first prepared by A .

Baeyer in 1868 . It may be synthetically obtained by distilling oxindole (C8H8NO) with zinc dust; by heating orthonitrocinnamic acid with potash and iron filings; by the reduction of indigo blue; by the action of sodium ethylate on orthoaminochlorstyrene; by boiling-aniline with dichloracetaldehyde; by the dry distillation of ortho-tolyloxamic acid; by heating aniline with dichloracetal; by distilling a mixture of calcium INDORE formate and calcium anilidoacetate; and by heating pyruvic acid phenyl hydrazone with anhydrous zinc chloride . It is also formed in the pancreatic fermentation of albumen, and, in small quantities, by passing the vapours of mono- and dialkylanilines through a red-hot tube . It crystallizes in shining leaflets, which melt at 52° C. and boil at 245° C . (with decomposition), and is volatile in a current of steam . It is a feeble base, and gives a cherry-red coloration with a pine shaving . Many derivatives of indole are known . B-methyl indol or skatole occurs in human faeces .