Farbbleichkatalysatoren fuer das Silberfarbbleichverfahren

摘要

2 - Sulpho - 3 - (p - sulphophenylazo - 4-hydroxy-benzo[a] -phenazine is prepared by adding diazotized 1-amino-benzene-4-sulphonic acid to an aqueous solution of 4-hydroxybenzo[a]-phenazine-2-sulphonic acid and adjusting the pH to 9.8 to 10. Azo-azines having the following formulae are said to be obtained by coupling diazotized mono-amines or tetrazotized diamines with the appropriate hydroxybenzophenazines Also 4-amino-benzene sulphonic acid is diazotized and coupled to 2-phenylamino-naphthalene-5-hydroxy-7-sulphonic acid, coupling in 6-position of naphthalene ring.