DOUBLE SULFATES OF COBALT(II), NICKEL(II), COPPER(II) AND ZINC(II) WITH TRIMETHYLAMMONIUM CATION - SYNTHESIS, IDENTIFICATION AND THERMAL-DECOMPOSITION

Double sulfates of Co(II), Ni(II), Cu(II) and Zn(II) were obtained by evaporation of the reaction mixture of the corresponding metal sulfate and trimethylammonium sulfate aqueous solution in molar ratio 1:6, at room temperature. The crystals obtained were identified and investiga ted by elemental analysis, TG, DTG and DTA analysis, X-ray powder diff raction and electronic spectroscopy. It was found that the double sulf ates of Co(II), Ni(II) and Zn(II) have the general empirical formula [ (CH3)3NH]2M(SO4)2 . 8H2O, but although obtained in the same manner, th e double sulfate of copper has the empirical formula [(CH3)3NH]2Cu2(SO 4)3 . 7H2O. The X-ray powder diffraction patterns of the compounds obt ained, show that the double sulfates of cobalt and zinc are isostructu ral, but although it has the same empirical formula, the double sulfat e of nickel seems not to be isostructural with them. The thermal decom position of the compounds is also discussed.