The volumetric and thermochemical properties of , , , and at K and MPa

Densities and apparent molar volumes of HClO4(aq) and Yb(ClO4)3(aq) at elevated temperatures and pressures

“…A sample of the commercial metal oxide, Yb 2 O 3 (0.999 mol fraction) (Aldrich Chemical Company, catalog number 24,699-9), was used, without further purification, to prepare an acidified perchlorate salt stock solution using a method that has been previously described in detail [2].…”

“…Initial work focused on the apparent and partial molar volumes and heat capacities of aqueous rare earth sulfates at T ¼ 298:15 K and p ¼ 0:1 MPa [1]. However, volumetric and calorimetric studies on aqueous rare earth perchlorate [2] and aqueous rare earth chloride salt solutions [3] have also been completed. Although experiments were performed over a range of temperatures (p ¼ 0:1 MPa) in the latter studies [2,3], the high temperature and pressure volumetric and thermochemical surfaces of these systems have remained unexplored with the exception of the volumetric studies by Xiao et al [4,5] on aqueous solutions of gadolinium and lanthanum trifluoromethanesulfonate.…”

“…However, volumetric and calorimetric studies on aqueous rare earth perchlorate [2] and aqueous rare earth chloride salt solutions [3] have also been completed. Although experiments were performed over a range of temperatures (p ¼ 0:1 MPa) in the latter studies [2,3], the high temperature and pressure volumetric and thermochemical surfaces of these systems have remained unexplored with the exception of the volumetric studies by Xiao et al [4,5] on aqueous solutions of gadolinium and lanthanum trifluoromethanesulfonate. In the absence of such experimental data, estimates of the temperature and pressure dependences of the apparent molar properties at infinite dilution for aqueous trivalent metal cation containing systems have been calculated using semiempirical equations of state [6].…”

“…Unfortunately, the predictive abilities of these models have remained untested. Aqueous rare earth salts are currently used in a wide variety of applications [1,3], some with significant socioeconomic importance, and therefore a more complete understanding of the thermodynamics of these systems could prove to be advantageous. In an attempt J. Chem.…”

“…T /K p/MPa q 1 /(kg Á m À3 ) q 3 À q 1 /(kg Á m À3 ) V /;3 /(cm 3 Á mol À1 ) dV /;3 /(cm 3 The concentration, temperature, and pressure surfaces of the apparent molar volumes for Yb(ClO 4 ) 3 (aq) and HClO 4 (aq) solutions have been modelled using modified Pitzer ion-interaction equations [12]. For Yb(ClO 4 ) 3 (aq) solutions, the temperature and pressure dependences of apparent molar volumes at infinite dilution have been modelled within the Pitzer ion-interaction equation framework using an equation of state of TABLE 2 The densities of pure water, q 1 , the concentration dependence of relative densities, q 3 À q 1 , apparent molar volumes of aqueous solutions of perchloric acid, V /;3 , and the uncertainties in apparent molar volumes, dV /;3 , at approximately T ¼ 373:15 K and p ¼ (10, 20 and 30) MPa the form proposed by Helgeson and co-workers [13,14].…”