Phase Equilibrium in the System RbCl−NdCl₃−HCl(13.26 %)−H₂O at 298.15 K and Standard Molar Enthalpy of Formation of New Solid Phase Compound

Abstract

The solubility of the quaternary system RbCl-NdCl 3 -HCl(13.26 %)-H 2 O at 298.15 K was determined, and the corresponding equilibrium diagram was constructed. The quaternary system consists of three equilibrium solid phases, RbCl, RbNdCl 4 • 4H 2 O (1:1 type), and NdCl 3 • 6H 2 O. The new solid phase compound RbNdCl 4 • 4H 2 O was found to be congruently soluble in the system. The compound RbNdCl 4 • 4H 2 O was characterized by X-ray diffraction, X-ray diffraction single crystal structure analysis, thermogravimetry, and differential thermogravimetry. It belongs to an orthorhombic system, with space group P21212, a ) 0.6986(6) nm, b ) 1.1319(1) nm, c ) 0.6665(6) nm, Dc ) 2.795 g • cm -3 , and Z ) 2. The compound loses its crystal water by one step at (370 to 474) K. The standard molar enthalpy of solution of RbNdCl 4 • 4H 2 O in deionized water was measured to be -(26.97 ( 0.24) kJ • mol -1 by heat conduction microcalorimetry. Its standard molar enthalpy of formation was calculated to be -(2732.3 ( 1.0) kJ • mol -1 .

Phase Equilibria in the Systems RbCl–TmCl3–HCl(22.12 %)–H2O and RbCl–LuCl3–HCl(21.37 %)–H2O at 298.15 K and Standard Molar Enthalpy of Formation of Rb2LuCl5·7H2O

“…Comparing the reported quaternary systems − with the present quaternary systems, the phase chemical reactions of the two quaternary systems RbCl–RECl 3 –HCl(∼22 %)–H 2 O (RE = Eu and Tm) were similar, because they are simple eutonic type. The new solid compounds RbRECl 4 ·4H 2 O of the 1:1 type (RE = La, Ce, Pr, Nd, Sm, and Gd) were formed in the quaternary systems RbCl–RECl 3 –HCl–H 2 O; however, the 2:1 type compound (Rb 2 LuCl 5 ·7H 2 O) was obtained in the quaternary system RbCl–LuCl 3 –HCl(21.37 %)–H 2 O.…”

“…The compounds of Er 3+ -doped RbGd 2 C1 7 and RbGd 2 Br 7 (1:2 type), which were synthesized by Riedener et al in the Bridgman technique, have upconversion fluorescence properties in the infrared region . To synthesize the new compounds from rubidium chloride and rare earth chlorides in using the phase equilibrium method and provide the phase relations and interactions of RbCl and RECl 3 in the HCl(∼13 % or ∼22 %)–H 2 O medium, equilibrium phase diagrams of the quaternary systems RbCl–RECl 3 –HCl(∼13 % or ∼22 %)–H 2 O (RE = La, Ce, Pr, Nd, Sm, Eu) were investigated in our previous studies. − In these systems, the quaternary systems RbCl–RECl 3 –HCl(∼13 % or ∼22 %)–H 2 O (RE = La, Ce, Pr, Nd, Sm) were complicated, and new solid phase compounds of the 1:1 type RbRECl 4 ·4H 2 O (RE = La, Ce, Pr, Nd, Sm) were formed. The result shows similarity in the behavior of La, Ce, Pr, Nd, and Sm trichlorides in aqueous salt systems with RbCl, whereas the quaternary systems RbCl–EuCl 3 –HCl(13.44, 22.75 %)–H 2 O were simple eutonic type.…”