​PICENE, C₂₂H₁₄, a hydrocarbon found in the pitchy residue obtained in the distillation of peat-tar and of petroleum. This is distilled to dryness and the distillate repeatedly recrystallized from cymene It may be synthetically prepared by the action of anhydrous aluminium chloride on a mixture of naphthalene and ethylene dibromide (R. Lespieau, Bull. soc. chim., 1891, (3), 6, p. 238), or by distilling α-dinaphthostilbene (T. Hirn, Ber., 1800, 32, p. 3341). It crystallizes in large colourless plates wi hich possess a blue fluorescence It is soluble in concentrated sulphuric acid with a green colour. Chromic acid in glacial acetic acid solution oxidizes it to picene-quinone, picene-quinone carboxylic acid, and finally to phthalic acid. When heated with hy driodic acid and phosphorus it forms hydrides of composition C₂₂H₃₄ and C₂₂H₃₆ (see F. Bamberger and F.D. Chattaway, Ann., 1805, 284, p. 61).