INDENE, a hydrocarbon found in the fraction of the coal tar distillate (see COAL TAR) boiling between 176° and 182° C and isolated from this material by means of the picrate (m.p. 98° C). It is a colourless mobile liquid boiling at 179.5-180.5° C with a specific gravity 1.04 at 15° C. Its chemical formula is and its constitution (II.) may be deduced from its be haviour on oxidation and reduction. The former process gives phthalic acid (I.), the latter hydrindene or indane (III.), an oil, b.p. 176° C.
Indene rapidly absorbs oxygen from air, and polymerizes to a resin utilizable in lacquers and varnishes.