Water-soluble double potassium and ammonium salts of iron(III) and manganese(II) with (hydroxyethylidene)diphosphonic acid

Abstract

A method to multifold increase the water solubility of diiron(III) tris[(hydroxyethylidene)-diphosphonate) tetrahydrate Fe2(H2L)3·4H2O and manganese(II) (hydroxyethylidene)diphosphonate dihydrate MnH2L·2H2O, prepared by the reaction of 1-hydroxyethylidene-1,1-diphosphonic acid with iron(III)hydroxide and basic manganese carbonate. The method involves conversion of the phosphonates into their double salts Fe2K6L3·4H2O [Fe2(NH4)6L3·4H2O] and MnK1.3H0.7L·2H2O [Mn(NH4)2L·2H2O] by treatment of their aqueous suspensions with potassium or ammonium hydroxides. The solubility of the iron salt increases from 0.2 to 4.0 g per 100 mL solution (20 times) and that of the manganese salt increases from 0.1 to 4.8 g per 100 mL solution (45 times).