A composition containinga) 25 to 87 wt.% of KHSO5 containing triple saltb) 1 to 20 wt.% of at least one H2N(CH2)nSO3H compound with n being 0, 1, 2 or 3,c) 1 to 8 wt.% of a surfactantd) 1 to 60 wt.% of a C2-C10 aliphatic dicarboxylic acid, optionally substituted with a hydroxyl and/or carboxylic group ande) 10 to 30 wt.% alkali metal phosphate.
