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 we re obtained as crystalline products by evaporation at room temperature of an aqueous mixture of Ln(III) sulphate and dimethylammonium sulpha te in molar ratio from 1:4 to 1:15, and treatment, in some cases, of t he concentrated mixture with ethanol. The identification was carried o ut by means of X-ray powder diffraction patterns. It was found that th ey are isostructural. On the basis of the thermal decomposition and ch emical analysis of the obtained double salts, their general empirical formula (CH3)2NH2Ln(SO4)2 . H2O was established. It was found that rar e earth(III) sulphates are obtained at 700-degrees-C. The thermal deco mposition takes place in two well-resolved stages. The decomposition o f the anhydrous double salts is not a simple dissociation, but involve s intermediate reactions.