THERMODYNAMIC PROPERTIES OF THE RARE-EARTH ELEMENT VAPOR COMPLEXES LAAL4CL15, CEAL4CL15 AND HOAL2CL9

Thermodynamic studies were carried out for the vapor complexes of alum inum chloride with lanthanum chloride at 588-673 K and 0.05-0.22 MPa, cerium chloride at 593-705 K and 0.04-0.11 MPa, and holmium chloride a t 756-838 K and 0.04-0.20 MPa, respectively, by quenching experiments. The results suggest that the coexistent complexes are LnAl(3)Cl(12) a nd LnAl(3)Cl(12) for Ln=La and Ce and LnAl(3)Cl(12) and LnAl(3)Cl(12) for Ln=Ho. Thermodynamic functions of the reaction LnCl(3)(s)+(v/2)Al2 Cl6(g)=LnAl(v)Cl(3v+3)(g) derived from the measurements are: Delta H(2 98)degrees=-56.9 kJ . mol(-1) and Delta S(298)degrees=-162.6 J . mol(- 1). K-1 for LaAl4Cl15, Delta H(298)degrees=-28.2 kJ . mol(-1) and Delt a S(298)degrees=-1115.8 J . mol(-1). K-1 for CeAl4Cl15, and Delta H(29 8)degrees=83.6 kJ . mol(-1) and Delta S(298)degrees=57.4 J . mol(-1). K-1 for HoAl2Cl9. (C) 1998 Elsevier Science S.A.