SYNTHESIS, IDENTIFICATION AND THERMAL-DECOMPOSITION OF DOUBLE SULFATES OF SOME LANTHANIDES AND Y WITH ETHANOLAMMONIUM CATION

On evaporation at room temperature of an aqueous mixture of Ln(III) su lphate and ethanol-ammonium sulphate in a molar ratio higher than 1:12 , in the presence of sulphuric acid, double sulphates of Sm, Eu, Ho, T m, Yb and Y with a waxy feel were obtained. The stoichiometry of the o btained compounds was determined by means of elemental and TG analysis . On the basis of X-ray powder diffraction patterns it was concluded t hat an isostructural group with a general formula: Ln(2)(HOCH2CH2NH3)( 8)(SO4)(7). 8H(2)O was obtained. The above compounds have a stoichiome try and a crystal structure different from those of the double sulphat es of La, Ce, Pr and Nd with the same monovalent cation, as presented earlier. The thermal decomposition of the investigated compounds in th e temperature range from ambient temperature up to 1173 K occurred in a similar way, mainly in three not well-differentiated steps. Lanthani de oxysulphates were obtained as final products.