The apparent molal volumes (Vφ) of the trivalent rare earth (La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and Y) chlorides, nitrates and perchlorates have been calculated from the density measurements at 25 C and (5 to 80) C and 0.02-4 m. The values of Vφ have been fitted to the Pitzer equations, Vφ = V̄0 + (A vI/(1.2m) ln(1 + 1.2I0.5) + 2RTm(βV(0) + βV(1) g(y) + mCV), where V̄0 is the infinite dilution partial molal volume, Av is the Debye-Hückel slope, I is the ionic strength, and g(y) = (2/y2)·[1-(1 + y) exp(-y)] where y = 2(I0.5). The Pitzer volume parameters βV(0), βV(1) and CV are functions of temperature. The values of V̄0, βV(0), βV(1), and CV for most of the rare earth chlorides are similar orders of magnitude. These results should be useful in estimating the effect of pressure on the equilibria of rare earths in natural waters over a wide range of temperature.
ASJC Scopus subject areas
- Chemical Engineering(all)