Experimental studies by electron microprobe analyses, optical microscopy, and differential scanning calorimetry were performed. New data about the liquidus in the central and the Bi-rich regions were obtained. A narrow homogeneity region (about 50-52 at.% Bi) was found for the compound NiBi while the second intermediate phase in this system (NiBi 3 ) was stoichiometric. Thermodynamic optimization of the Ni-Bi phase diagram was achieved by the CALPHAD method by combining phase diagram and thermodynamic data. Thus, NiBi was modeled with two sublattices, allowing mixing of Bi and Ni on one of them only. The intermetallic phase NiBi 3 was modeled as a stoichiometric compound. Redlich-Kister polynomials were used to describe the excess Gibbs energies of the solution phases (liquid, pure bismuth, and Ni-based solid solutions).

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Bismuth thermodynamic activities in Ni – Bi liquid solutions have been measured by the modified isothermal isopiestic method at 1723, 1753 and 1773 K. These results are coupled with thermochemical and topological data from literature, in order to achieve reliable re-optimization of the Ni – Bi system by the CALPHAD method. The model of disordered substitutional solutions has been applied to the liquid phase and to the face-centered cubic solid solutions (Ni). The compound NiBi3 is stoichiometric and is modeled by a two-sublattice model corresponding to its formula. The nickel solubility in the solid bismuth is negligible, which is why the phase (Bi) is considered as consisting of bismuth only. The description Bi: Ni, Va has been used for the thermodynamic modeling of the nonstoichiometric NiBi phase.

If the internal wall of the diffusion column used in the reversed-flow gas chromatography (RFGC) technique is covered with an adsorbent material or a supported liquid, then isotherm determination becomes much simpler.Diffusion and resistance to mass transfer are not neglected, the sorption effect is non-existent and the pressure gradients are negligible along the bed. The method leads directly to independent experimental isotherms over a wide range of concentrations, without specifying a priori an isotherm equation. The isotherm can also be determined in the presence of a surface reaction of the adsorbate. The necessary theoretical analysis has been developed, and the equations derived were applied to benzene and cyclohexane adsorbed on graphitized carbon black, to ethene, ethyne, propene and sulfur dioxide on marble powder, and to propene on silica gel.

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