Standard Sublimation Enthalpies of Erbium Trichloride, Tribromide, and Triiodide

Abstract

The total vapor pressures of the erbium trihalides ErCl3, ErBr3, and ErI3 were measured by the torsion method, and their temperature dependences can be expressed by the following equations over the given temperature ranges: ErCl3(s), log(p/kPa) = 12.04 ± 0.15 − (15159 ± 200)(K/T) from (880 to 1040) K; ErBr3(s), log(p/kPa) = 11.09 ± 0.15 − (14256 ± 200)(K/T) from (919 to 1058) K; ErI3(s), log(p/kPa) = 11.55 ± 0.15 − (13862 ± 200)(K/T) from (871 to 1082) K. Treating the results by second- and third-law methods, the standard sublimation enthalpies were determined to be Δsub H°(298 K) = {(308 ± 4) kJ·mol-1 and (293 ± 4) kJ·mol-1} for ErCl3 and ErBr3, respectively. For ErI3 the proposed enthalpy, Δsub H°(298 K) = (282 ± 6) kJ·mol-1, was only derived by the second-law method. From this standard enthalpy a set of free energy functions for solid ErI3 was evaluated by third-law treatment of the data.

Vapor Pressures and Standard Sublimation Enthalpies for Thulium Trichloride, Tribromide, and Triiodide

“…Pressures of solid trichlorides for A, La; B, Ce; C, Pr; D, Nd; E, Sm; F, Ho; G, Er; H, Dy; I, Tb; L, Tm (this work). The pressure values for ErCl 3 (G) and TmCl 3 (L) are practically equal.…”

“…The average third-law enthalpy value, Δ sub H °(298 K) = 282.5 kJ·mol -1 , obtained by using the Pankratz's fef for TmBr 3 (g), is higher than the average enthalpy value (278 kJ·mol -1 ) obtained by Gietmann's fef but is in better agreement with the second-law result (290 ± 5 kJ·mol -1 ). On this basis, considering the uncertainties in the fef and enthalpy function for both the solid and gaseous phases, we propose as standard sublimation enthalpy for TmBr 3 the value: Δ sub H °(298 K) = 285 kJ·mol -1 , with an estimated error that should not exceed ±5 kJ·mol -1 , a value slightly higher than the final value (280 ± 6) kJ·mol -1 proposed by Gietmann et al

7 Pressures of solid trichlorides for A, La; B, Ce; C, Pr; D, Nd; E, Sm; F, Ho; G, Er; H, Dy; I, Tb; L, Tm (this work). The pressure values for ErCl 3 (G) and TmCl 3 (L) are practically equal.

8 Comparison of the free energy function [( G °( T ) − H °(298 K)]/ T for solid lanthanides triiodide reported by Pankratz: 22 ▪, LaI 3 ; ○, CeI 3 ; ·, PrI 3 ; ▵, NdI 3 ; ▴, GdI 3 ; ×, TbI 3 ; □, HoI 3 ; ◇, ErI 3 ; +, TmI 3 (this work).

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“…This work is part of a continuing systematic study − carried out in order to obtain accurate measurements of the vapor pressures of rare-earth trihalides and to derive their standard sublimation enthalpies. In particular, the aim of the present paper was to determine the standard sublimation enthalpies of thulium trichloride, tribromide, and triiodide measuring their vapor pressures.…”

Vaporization Study of YbCl3, YbBr3, YbI2, LuCl3, LuBr3, and LuI3 and a New Assessment of Sublimation Enthalpies of Rare Earth Trichlorides

“…For a consistent comparison of these results with the standard sublimation enthalpies of other rare earth trichlorides previously studied by us, − the vapor pressures of these compounds were treated by the second- (2-L) and third-law (3-L) method employing the new sets of enthalpic increments and fef . The standard sublimation enthalpy values so obtained are summarized in Table .…”

“…The present work is the last of our systematic study − on the vaporization thermodynamics of rare earth trihalides carried out in order to determine their sublimation enthalpies from vapor pressure measurements. In this paper, the sublimations of ytterbium trihalides (YbCl 3 and YbBr 3 ), ytterbium diiodide, and lutetium trihalides (LuCl 3 , LuBr 3 , and LuI 3 ) were studied.…”