STUDIES ON THE THERMAL-DECOMPOSITION OF RARE-EARTH ELEMENT COMPLEXES WITH 2-NAPHTHOIC ACID

The rare earth element 2-naphthoates were prepared as crystalline solids sparingly soluble in water water (10(-5)-10(-6) mol . dm(-3)), with general formula Ln(C10H7COO)(3) . nH(2)O, where n = 3 for La-Gd, n = 2 for Tb and Dy, and n = 0 for Y and Ho-Lu. During heating, the di- and trihydrated rare earth 2-naphthoates lose the crystallization water molecules and the anhydrous complexes then decompose directly to Ln(2)O(3), CeO2, Pr6O11 or Tb4O7 Formation of an intermediate is observed only in the case of the anhydrous lanthanum complex, which decomposes to La2O3 via La2O2CO3. The anhydrous complexes of Ho-Lu decompose directly to Ln(2)O(3) in one step when heated. The anhydrous rare earth 2-naphthoates are very stable (up to 578-683 K).