OXINDOL. 389 



Oxindol, C 8 H 7 ^"0. Is formed by further reduction 

 of dioxindol with tin and hydrochloric acid or with 

 sodium-amalgam in a dilute solution, kept constantly 

 acid. Long, colorless needles or feathery groups. 

 Difficultly soluble in cold water, easily soluble in hot 

 water and in alcohol; fuses at 120 ; and in small quan- 

 tities, it can be distilled without undergoing decom- 

 position. When its aqueous solution is evaporated in 

 contact with air, it becomes partially oxidized again, 

 forming dioxindol. Like dioxindol, it yields crystal- 

 lizing salts with acids, as well as bases. Nitrous acid 

 transforms it in very dilute aqueous solutions into 

 nitroso-oxindol, C 8 H 6 (JTO)NO, a substance that crystal- 

 lizes in long, golden needles, difficultly soluble in 

 water. 



Indol, C 8 IKN". Is formed when the vapors of oxin- 

 dol are conducted over heated zinc-dust ; or when in- 

 cligo-blue is boiled with zinc and hydrochloric acid 

 until it is converted into a brownish -yellow powder, 

 and this then distilled with an excess of zinc-dust. It 

 is also formed in small quantity when nitrocinnamic 

 acid is fused with potassium hydroxide with an addi- 

 tion of iron filings. Large, colorless laminse similar to 

 benzoic acid ; fusing point, 52 ; not distillable alone, 

 but very well with water vapor. Very weak base. 

 With hydrochloric acid, it forms a difficultly soluble 

 salt, which, when boiled with water, yields free indol. 



Isatyde, C 16 H 12 N 2 O, is formed by heating isatin 

 with dilute sulphuric acid ; or when its warm saturated 

 alcoholic solution is mixed with ammonium sulphy- 

 drate in a closed flask, and allowed to stand for some 

 time, it being deposited gradually in the form of crys- 

 talline scales. It bears the same relation to isatin, as 

 indigo-white bears to indigo-blue. Colorless, fine crys- 

 talline inodorous and tasteless substance, insoluble in 

 water, but slightly in alcohol. 



Sulphisatyde, C 16 H 12 N 2 2 S 2 . When sulphuretted 

 hydrogen is conducted into an alcoholic solution of 



