8203. Newton, P. A., [Farbenfabriken vorm. F. Bayer & Co.]. April 1. Indigoid dyes are obtained by condensing alphaketo derivatives of isatin or its homologues or halogen derivatives (in which the alpha-keto oxygen is replaced by easily removable groups such as halogen, sulphur, the amino group or the alkoxy group) with 1-naphthol or 1-anthrol or derivatives thereof having free ortho- and para-positions to the hydroxy group, and introducing one atom of chlorine into the products by means of sulphuryl chloride; the chlorine enters in paraposition to the hydroxy group; according to examples the condensation products from alphaisatinanilide or dibromisatin chloride and 1- naphthol are chlorinated.