Measurement Of The Osmotic Coefficients Of The Cobalt Aqueous Solution

Cobalt which is an important component in all kinds of functional materials, has much excellent performance such as heat-resisting, wear-resisting, high strength and high magnetic properties. Cobalt, as one of important metal elements in space technology material shows its importance in great demand of the properties. As one of the important carrier of the Cobalt element, the thermodynamic properties of the Cobalt chloride aqueous solution in metallurgy industry, acts an important role. The main study content in this paper is described in the following:(1) The osmotic coefficients and water activities of the COCl2-H2O system at303.15K have been determined by isopiestic method, The results have been represented by the Pitzer model. The Pitzer ion interaction parameters were evaluated from experimental data by using multiple regressions. And the results of the pure salt parameter are represented as follows:βCoCl2(0)=0.35790,βCoCl2(1)=1.71314, CCoCl2Φ=-0.01375. The osmotic coefficient and the ion activity coefficient of the system have been calculated by the Pitzer model, thus the changing rules of the osmotic coefficient and the mean activity coefficient have been represented well by the calculation.(2) The osmotic coefficients and water activities of the ternary system CoCl2-NiCl2-H2O at298.15K have been determined by isopiestic method. The results have been represented by the Pitzer model. The Pitzer ion interaction parameters were evaluated from experimental data by using multiple regressions, and the results are represented as follows: θ=-0.02802,Ψ=0.0070. The relative deviation of osmotic coefficients and water activities between the experimental data and that calculated from the Pitzer model act well enough to describe the thermodynamic properties. The mean activity coefficients of CoCl2and NiCl2in the CoCl2-NiCl2-H2O system were obtained from the Pitzer model, and their variations with ionic strength was established by calculations.