SYNTHESIS AND THERMAL-DECOMPOSITION OF SOME RARE EARTH(III) DIMETHYLAMMONIUM SULFATE CRYSTALLOHYDRATES .1. RESULTS OF INVESTIGATIONS OF (CH3)2NH2LN(SO4)2.H2O (WHERE LN IS LA-GD)

The double sulphates of some rare earths(III) with dimethylammonium were obtained as crystalline products by evaporation at room temperature of an aqueous mixture of Ln(III) sulphate and dimethylammonium sulphate in molar ratio from 1:4 to 1:15, and treatment, in some cases, of the concentrated mixture with ethanol. The identification was carried out by means of X-ray powder diffraction patterns. It was found that they are isostructural. On the basis of the thermal decomposition and chemical analysis of the obtained double salts, their general empirical formula (CH3)2NH2Ln(SO4)2 . H2O was established. It was found that rare earth(III) sulphates are obtained at 700-degrees-C. The thermal decomposition takes place in two well-resolved stages. The decomposition of the anhydrous double salts is not a simple dissociation, but involves intermediate reactions.