Thermodynamical study on the magnesium selenate-nickel selenate-water system at 25�C

Thermodynamic study of the co-crystallization of 2RbCl·NiCl2·2H2O and 2RbCl·MnCl2·2H2O, at the temperature 298.15 K

“…The authors (28) have calculated the Gibbs free energy of mixing of crystals D mix G m by the following equation: (2) where x i is the mole fraction of component i in the mixed crystals, a is the activity, and the indices s, l, and l 0 refer to mixed crystals, and saturated ternary and binary solutions, respectively. In previous studies (26,29,30) we proved the applicability of these equations to the determination of D mix G m for a series of systems in which mixed crystals of both anhydrous salts and crystalline hydrates are formed.…”

“…This means that the interionic interactions of the type M-N and M-N-X in ternary solutions of the type (m 1 MX+m 2 NX)(aq), from which mixed crystals crystallize, are very weak and that the ternary parameters may be neglected (u MN =c MNX =0). This approach has been proposed by Pitzer and Kim (24) for a series of solutions and has been used successfully for simulation of systems where mixed crystals are formed by anhydrous salts (alkali halides (26,29,35) ) as well as by crystalline hydrates (sulphate heptahydrates), (29) selenate hexahydrates, (30) and halide hexahydrates). (26) Values of the ternary parameters used by as are given in This work was supported by the Bulgarian Ministry of Science and Education, Project X-594.…”

Thermodynamic study of (m1Cs2SeO4+m2NiSeO4)(aq)wheremdenotes molality atT= 298.15 K

“…The salts obtained were recrystallized twice with distilled water at room temperature in a desiccator above concentrated sulfuric acid and dried in air. (1,2,(4)(5)(6) The osmotic coefficients of the Cs 2 SeO 4 (aq) solutions were determined by the isopiestic method described by Ojkova et al, (1,4) Christov et al, (2) and Stoilova et al (5) The solutions were prepared by the gravimetric method. The salts were weighed with an accuracy of ±1 · 10 −5 g giving, after the addition of 3 ml of water, a solution of the desired concentration.…”

“…(15) It has been shown that Pitzer equations can describe the properties of binary (1,2,4,13) and multicomponent (16,17) solutions in which phases with a constant composition (simple and double salts) (16)(17)(18)(19)(20) and solid solutions (3,5) crystallize.…”

Thermodynamics of the formation of solid solutions of the type (Me,Me′)SeO4·6H2O where Me and Me′ denote Mg, Co, Ni, or Zn from aqueous solutions

“…It is of both theoretical and practical importance to establish the regularities of formation of selenate mixed crystals from aqueous solutions and to determine the most important thermodynamic characteristics of this process. Ojkova et al (1)(2)(3) and Stoilova et al (4) have investigated the ternary solutions of the type (m 1 MeSeO 4 + m 2 Me'SeO 4 )(aq) where Me and Me' denotes Mg, Co, Ni, or Zn and established the formation the mixed crystals of the type (Me,Me')SeO 4 ·6H 2 O. After isopiestic determination of the dependence of the activity of water a w on the molality m of the binary and ternary solutions and using different extrapolation methods (5,6) the same authors have determined the activity coefficients in the liquid g i and in the mixed crystalline f i phases.…”