SYNTHESIS, IDENTIFICATION AND THERMAL-DECOMPOSITION OF DOUBLE SULFATES OF LA, CE, PR OR ND WITH ETHANOLAMMONIUM

On evaporation at room temperature of an aqueous reaction mixture of L n(III) sulfate and ethanolammonium sulfate in a molar ratio higher tha n 1:16, crystal products with a waxy feel were obtained. They were ide ntified by means of the X-ray powder diffraction patterns and it was c oncluded that they are isostructural. The results of elemental analysi s and the mass losses by TG analysis indicated the formation of double sulfates with general formula: (HOCH2CH2NH3)(4)Ln(2)(SO4)(5) . 4.5H(2 )O (Ln = La, Ce, Pr or Nd) Their thermal decompositions in static atmo sphere in the temperature range from ambient up to 1173 K took place i n a similar way, and mainly Ln(2)O(2)SO(4) was obtained as final produ ct. The exception was the Ce compound, which decomposed to CeO2. The d ouble sulfates decomposed in many not well-differentiated steps. From the mass losses occurring during thermal decomposition, the mode of th ermal decomposition was presumed. The X-ray powder diffraction pattern s of Ln(2)O(2)SO(4) (Ln = La, Pr and Nd) show that they are also isost ructural.