ChemInform Abstract: DENSITIES AND THERMAL EXPANSION OF SOME AQUEOUS RARE EARTH CHLORIDE SOLUTIONS BETWEEN 5 DEGREES AND 80 DEGREES C PART 1, LACL3, PRCL3, AND NDCL3

Enthalpies of Dilution of NdCl3(aq) at Temperatures from 297.89 K to 372.08 K and an Extended Pitzer Ion-Interaction Model for the NdCl3 + H2O System

“…On the basis of the volumetric data for NdCl 3 (aq) reported by Gildseth et al, 15 we concluded that the effect on ∆ dil H m from changing the pressure from 0.5 MPa to 0.1 MPa is completely negligible compared to the direct experimental uncertainties of the ∆ dil H m values.…”

“…Although these association constants imply that formation of the monochloroneodymium(III) and dichloroneodymium(III) complexes may become extensive at higher molalities, these complexes are believed to be of the outer sphere type. 6,7,9,15,39 The calculations reported by Pitzer et al 32 at 298.15 K imply that the thermodynamic effects of a The initial and final molalities are mi and mf, respectively, Tave is the mean temperature for each series of measurements; all measurements were made at the fixed pressure 0.5 MPa. The values of σrms(∆dilHm) are the unweighted root mean square errors for the individual series of experiments relative to the accepted extended Pitzer model fit.…”

“…Densities of NdCl 3 (aq) were reported in three studies from Spedding's laboratory. 9,13,15 Very precise values of the "specific gravities" (i.e., the density ratio of solution to water) at 298.15 K were reported by Spedding et al 13 for molalities of from 0.001 907 mol‚kg -1 to 0.352 21 mol‚kg -1 using a magnetically controlled float apparatus and from 0.025 985 mol‚kg -1 to 3.9292 mol‚kg -1 using pycnometry, 9 where the highest molality is that of the saturated solution. Gildseth et al 15 also measured the densities of NdCl 3 (aq) for temperatures of 278.206 K to 352.891 K using a mercury displacement dilatometer.…”

“…9,13,15 Very precise values of the "specific gravities" (i.e., the density ratio of solution to water) at 298.15 K were reported by Spedding et al 13 for molalities of from 0.001 907 mol‚kg -1 to 0.352 21 mol‚kg -1 using a magnetically controlled float apparatus and from 0.025 985 mol‚kg -1 to 3.9292 mol‚kg -1 using pycnometry, 9 where the highest molality is that of the saturated solution. Gildseth et al 15 also measured the densities of NdCl 3 (aq) for temperatures of 278.206 K to 352.891 K using a mercury displacement dilatometer. Gildseth et al determined their solution molalities by measuring densities in the vicinity of 298 K, interpolating the measured density values to 298.15 K, and then back-calculating the molalities from variation of the density with molality obtained from the pycnometric measurements, 9 which guarantees consistency between the results of these two studies.…”

“…9 In addition, they reported measurements at lower molalities of the emf's of concentration cells with transference for NdCl 3 (aq), 10,11 enthalpies of dilution, 12 densities/partial molar volumes, 13 and also enthalpies of solution of NdCl 3 (cr) and NdCl 3 ‚6H 2 O(cr) in water. 7,12,14 Their only thermodynamic study of NdCl 3 (aq) at other temperatures is of the densities/apparent molar volumes at temperatures from 278.206 K to 352.891 K. 15 A few thermodynamic studies for NdCl 3 (aq) have been reported at other laboratories: isopiestic measurements at 298.15 K 16,17 and 293.15 K, 18 emf measurements for concentration cells with transport at 293.15 K, 18 and enthalpies of solution of NdCl 3 (cr) in water at 298.15 K 19 and for the temperature range (287.95 to 365.99) K. 20 Cordfunke and Konings 21,22 have critically assessed the enthalpies of formation and of solution of various RCl 3 (cr), where R denotes a rare earth element, and recommended ∆ f H°m(NdCl 3 (cr), T ) 298.15 K) ) -(1040.9 ( 1.0) kJ‚mol -1 and ∆ f H°m(Nd 3+ (aq), T ) 298.15 K) ) -(694.8 ( 2.0) kJ‚mol -1 . Spedding et al 23 similarly obtained ∆ sol H°m(NdCl 3 ‚6H 2 O(cr), T ) 298.15 K) ) -(38.14 ( 0.17) kJ‚mol -1 as the average from three concordant studies,…”