Solvation phenomena and revision of solid–liquid equilibria in aqueous solutions of two precursors of mixed oxides, the hydrates of cobalt and nickel nitrates

Linear behaviour in isothermal equilibria involving saturated electrolyte solutions: The H 2 O–Co(NO 3 ) 2 –Ni(NO 3 ) 2 ternary system at low temperature

“…The phase equilibria of the H 2 O-Co(NO 3 ) 2 and H 2 O-Ni(NO 3 ) 2 binary systems were already modelled, taking into account ion solvation in solution [8]. Indeed, though the existence of di-, tetra-and hexahydrate has been established, some uncertainty remains about the other hydration degrees, such as cobalt nitrate enneahydrate.…”

“…In the quasi-ideal model [8], the molar fraction X H 2 O only depends on temperature, as shown in the Eq. (10):…”

“…Table 2 provides the solubility constant values for hydrated cobalt and nickel nitrates, which are calculated using the quasi-ideal model [8], and the ice liquidus equation at 248.15 K and 258.15 K.…”

“…3. The M 1 , M 2 and M 13 mixtures are located on the binaries H 2 O-Ni(NO 3 ) 2 and H 2 O-Co(NO 3 ) 2 , which were studied previously [8]. As the stable solid phase of the nickel nitrate at this temperature is the enneahydrate, the observed hexahydrate is then in a metastable equilibrium.…”

“…It also has the advantage of describing physical and chemical interactions in solution and particularly solvation phenomena. It is based on the fundamental assumption of the model [8]:…”