GB274226A - A new method for the preparation of indanthrone-disulphonic acids and indanthrone - Google Patents

Abstract

274,226. British Dyestuffs Corporation, Ltd., Shepherds on, A., and Hailwood, A. J. April 26, 1926. 1-Hydroxylaminoanthraquinone - 8 - sulphonic acid; aminohydroxyanthraquinone sulphonic acids; indanthrone; indanthrone disulphonic acid. - 1-Nitroanthraquinone-8-sulphonic acid is reduced in neutral or alkaline solution with less reducing agent than is necessary for reduction to the amino compound. The product, which is probably 1 - hydroxylaminoanthraquinone - 8 - sulphonic acid, yields an indanthronedisulphonic acid on heating with alkali. The sulphonic groups can be split off from the latter, for example, by electrolytic reduction in a divided cell according to the method described in Specification 273,043, [Class 41, Electrolysis]; since the disulphonic acid first becomes reduced to the leuco compound, the latter may be prepared by reduction with hydrosulphite prior to the electrolytic reduction. According to examples the 1- nitroanthraquinone-8-sulphonic acid is reduced with sodium sulphide, zinc dust and ammonium chloride, or glucose; the 1-hydroxylaminoanthraquinone-8-sulphonic acid so obtained yields aminohydroxyanthraquinonesulphonic acid d (1 : 2 : 8 or 1 : 4 : 8 or a mixture of both) by treatment with concentrated sulphuric acid, and an indanthronedisulphonic acid by heating with caustic alkali; the latter dyes cotton from the vat in fugitive shades and wool from an acid bath. In a further example, the indanthronedisulphonic acid dissolved in alkaline hydrosulphite solution is subjected to electrolytic reduction in a divided cell using a mercury cathode, an iron anode, and a caustic soda anolyte; the product is a solution of leuco-indanthrone which yields indanthrone on oxidation.