A magenta pyrazolone azomethine dye was prepared by oxidative coupling of p -diethylaminoaniline with 1-phenyl-3-methyl-5-pyrazolone. The dye was bleached in buffered EtOH-H₂O solution containing excess sodium sulphite. The reaction rate of the dye bleaching was observed in the range of pH 5-10, several ten minutes, at 85°C, in N₂ gas. Regeneration ratio of the dye was about 100% by addition of HCHO, while it was only 3-5% in the case of K₂S₂O₈ adding. The reaction scheme was concluded as follows: the main reaction dye+SO₃^2-+H⁺→H·dye·SO₃^-complex (1) the side reaction dye+SO₃^2-+H2O→leuco dye+SO₄^2- (2)