Vapor pressures and sublimation enthalpies of praseodymium trichloride, tribromide, and triiodide

The vapor pressures for praseodymium trihalides, PrCl3, PrBr3, and PrI3, we re measured above solid and liquid phases by the torsion method. In the cov ered temperature ranges, their values can be expressed by the following equ ations: PrCl3(s), lg(p/kPa) = 12.45 +/- 0.20 - (16540 +/- 200) K/T (from 96 3 to 1045 K); PrCl3(1), lg(p/kPa)= 9.56 +/- 0.10 - (13422 +/- 150) K/T (fro m 1060 to 1131 K); PrBr3(s), lg(p/kPa) = 12.06 +/- 0.30 - (15060 +/- 200) K /T (from 890 to 961 K); PrBr3(1), lg(p/kPa) = 9.55 +/- 0.30 - (12698 +/- 20 0) K/T (from 967 to 1061 K); PrI3(s), lg(p/kPa)= 11.31 +/- 0.30 - (13766 +/ - 200) K/T (from 889 to 1003 K); PrI3(1), lg(p/kPa) = 8.36 +/- 0.35 - (1081 6 +/- 300) K/T (from 1013 to 1127 K). The standard sublimation enthalpies ( Delta H-sub degrees (298 K) = 330 +/- 10, 300 +/- 10, and 278 +/- 5 kJ mol( -1) for PrCl3, PrBr3, and PrI3, respectively) were determined by second- an d third-law treatment of the vapor pressure data.