EXPERIMENTAL AND MODEL STUDIES OF SOLID-L IQUID EQUILIBRIA OF THE BINARY-SYSTEMS WATER-YTTRIUM NITRATE, WATER-BARIUM NITRATE AND WATER-COPPER NITRATE .1. THE BINARY-SYSTEMS H2O-BA(NO3)2 AND H2O-Y(NO3)(3)
R. Bouchet et al., EXPERIMENTAL AND MODEL STUDIES OF SOLID-L IQUID EQUILIBRIA OF THE BINARY-SYSTEMS WATER-YTTRIUM NITRATE, WATER-BARIUM NITRATE AND WATER-COPPER NITRATE .1. THE BINARY-SYSTEMS H2O-BA(NO3)2 AND H2O-Y(NO3)(3), Thermochimica acta, 241, 1994, pp. 229-246
An experimental study of solid-liquid equilibria of H2O-Ba(NO3)(2) and
H2O-Y(NO3)(3) systems has been conducted using conductimetry and cont
rolled thermal flux analysis. The solid phases were studied using X-ra
y diffraction, thermogravimetry and chemical analysis such as calcinat
ion and DCP. Calorimetric analysis using DSC on the water-barium nitra
te eutectic has given the transformation enthalpy (303 J g(-1)) and th
e specific heat capacities of the solid and the liquid mix between -20
and 15 degrees C. The invariant transformation temperatures of the H2
O-Y(NO3)(3) system have been determined or qualified and the measured
metastable melting point of the tetra-, penta- and hexahydrate are res
pectively 120.4, 77.8 and 51.8 degrees C. A thermodynamic study of the
phase equilibria of the two systems has been achieved taking into acc
ount ionic dissociation and solvation phenomena. It shows that the bar
ium nitrate in aqueous solution behaves as a binary electrolytic compo
und, that the yttrium nitrate in aqueous solution is dissociated and t
hat the yttrium ion tends to solvate itself mainly into tetra-, octa-
and dodecahydrate. The model used provides an excellent representation
of the equilibrium curves. The metastable fusion enthalpies of the va
rious hydrates have been computed and the validity check of these valu
es has been successfully conducted on yttrium nitrate pentahydrate.