Vapor Pressures and Sublimation Enthalpies of Gadolinium Trichloride, Tribromide, and Triiodide and Terbium Trichloride, Tribromide, and Triiodide

The equilibrium vapor pressures over GdCl3, GdBr3, GdI3, TbCl3, TbBr3, and TbI3 were measured by the torsion effusion method. The obtained data are well represented in the covered temperature ranges by the following selected equations: GdCl3(l)log(p/kPa)=9.50±0.30-(13113±300)(K/T)(from 930 to 1213 K) GdBr3(s)log(p/kPa)=11.46±0.20-(14355±200)(K/T)(from 895 to 1057 K) GdBr3(l)log(p/kPa)=9.75±0.30-(12671±400)(K/T)(from 1060 to 1179 K) a-GdI3(s)log(p/kPa)=10.99±0.20-(13651±200)(K/T)(from 890 to 1012 K) TbCl3(l)log(p/kPa) = 9.13±0.20 - (12210±200)(K/T) (from 921 to 1117 K) TbBr3(s)log(p/kPa) = 11.09±0.20 - (14013±200)(K/T)(from 904 to 1108 K) TbI3(s)log(p/kPa) = 11.33±0.30-(13850±400)(K/T)(from 861 to 1078 K) Considering the vapor consists only of the monomeric form, by the second- and third-law treatment of the experimental data the following standard sublimation enthalpies, at 298n K, of the compounds were derived: (311±4, 292±2, 279±2, 296±4, 288±4, and 279±2) kJ mol-1 for GdCl3, GdBr3, GdI3, TbCl3, TbBr3, and TbI3 respectively.