Sublimation study of BiCl3 and of BiBr3

The sublimations of BiCl3(s) and of BiBr3(s) have been studied by the torsion and the Knudsen-effusion methods. The measured vapour pressures can be expressed in the temperature range covered by the equations: BiCl3(s): log10(p/kPa) = (10.6±0.2)-(5.63±0.10)×103(T/K), (390 to 475 K), BiBr3(s,I): log10(p/kPa) = (10.3±0.2)-(5.49±0.15)×103(T/K), (400 to 431 K), BiBr3(s,II): log10(p/kPa) = (9.3±0.2)-(5.10±0.15)×103(T/K), (431 to 478 K),. The standard sublimation enthalpies were calculated by second- and third-law treatments and compared with the values reported in literature. The average values ?Hsub o(298.15 K) = 116.5 and 112.4 kJ·mol-1 for BiCl3 and BiBr3 respectively were derived.