Crystal data for a third polymorph (γ) of C.I. Pigment Red 1,1-[(4-nitrophenyl)azo]-2-naphthol

The preliminary single-crystal data and powder pattern are given for a third polymorph of C.I. Pigment Red 1. The powder pattern has been indexed using the single-crystal dimensions; the problems of multiple indexing have been reduced by comparison with single-crystal intensities and calculated structure factors.