Vaporization studies of lanthanum trichloride, tribromide, and triiodide

The total vapor pressures of the lanthanum trihalides LaCl3, LaBr3, and LaI 3 were measured by the torsion method, and their temperature dependence can be expressed by the following selected equations in the covered temperatur e ranges: LaCl3(s): log(p/kPa) = (12.31 +/- 0.10) - (17012 +/- 100) K/T (10 06-1122 K). LaCl3(l): log(p/kPa) = (9.65 +/- 0.23) - (13989 +/- 272 K/T (11 37-1188 K), LaBr3(s): log(p/kPa) = (11.71 +/- 0.20) - (15392 +/- 150 K/T (9 55-1045 K). LaI3(s): log(p/kPa) = (11.10 +/- 0.20) - (14098 +/- 200 K/T (93 2-1038 K). LaI3(l): log(p/kPa) = (8.39 +/- 0.15) - (11306 +/- 200 K/T (1055 -1123 K). Treating by second- and third-law methods the obtained results, t he standard sublimation enthalpies, Delta(sub)H degrees(298 K) = 334 +/- 5, 308 +/- 5, and 285 +/- 3 kJ mol(-1) for LaCl3, LaBr3, and LaI3, respective ly, were determined.