SYNTHESIS AND DEHYDRATION OF DOUBLE OXALATES OF RARE EARTHS(III) WITHSOME MONOVALENT METALS .1. SYNTHESIS AND THERMAL-BEHAVIOR OF KLN(C2O4)(2)CENTER-DOT-NH(2)O

The synthesis of double oxalates of rare earths(III) and potassium wit h empirical formulae K(4)Ln(2)(C2O4). 10H(2)O (Ln=La, Ce) and KLn(C2O4 )(2) . nH(2)O (where n=4 for Pr-Dy and n=4.5 for Ho-Lu, Y) is describe d. The compounds obtained were studied by TG, DTG and DTA over the tem perature interval 25-500 degrees C and by X-ray powder diffraction and chemical analysis. Three structurally different groups were recognize d. It was found that either rare earth oxide or basic carbonate (Ln(2) O(2) . CO3) and potassium carbonate were obtained as final product at 500 degrees C, depending on the rare earth element. The thermal decomp osition takes place in two well-resolved stages.