Molten salts equilibrium concentrations

The process is done at 740°C in a molten salt consisting of NaCl-KCl-PuCl3-MgCl2, under near-equilibrium conditions. Virtually all of the impurities concentrate in the anode. Of the impurities usually present in plutonium, only americium concentrates in the salt. 

The surface tension reflects the nature of chemical bonds between species of the system under question. Since molten salts are ionic in character, the surface tension is predominantly given by the chemical nature of the present ionic species. Due to different coulombic interactions between species, the ions more covalent in character are concentrated on the surface and become surface active. Therefore the concentration dependency of the surface tension of binary systems will be substantially influenced by the ionic composition. Due to the equilibrium between the bulk and the surface, the course of the... 

The most convenient method used widely for acidity (basicity) determination in various ionic media is the potentiometric method using an indicator electrode which is reversible to oxide ions. Usually, the measurements are performed in cells with a liquid junction. The most common scheme of an electrochemical cell used to measure the equilibrium concentration of oxide ions in molten salts is as follows ... 

The remainder of this chapter centers upon the calculation of the equilibrium properties of MM-level models. Such models with ion concentrations of up to 10 molecules/cm correspond to ionic solutions with total ionic concentrations up to about 1M. This concentration is roughly a tenth of the ionic concentration in a molten salt it is low enough so that many approximation methods that are quite satisfactory for BO-level models at densities up to a tenth that of the liquid may be used to calculate the measurable properties of MM-level models for the solutions. A typical approximation method of this kind is the HNC integral equation (Section 7). 

This reaction equilibrium determines the saturation concentration of NiO ions in presence of solid NiO. The activity (concentration) of NiO ions in the molten salt depends on the partial pressure of oxygen and on the activity of the 0 ions ... 

FIGURE 9.1. Coulometric titration curves for the systems Li-Sb and Li-Bi using a molten salt electrolyte for lithium ions. The equilibrium cell voltage is plotted with reference to elemental lithium as a function of the lithium concentration. 

Equilibrium concentrations for these components will strongly depend on the solvent system. Examination of the free energies of formation for the various alloy components shows that chromium is the most active of the metal components. Therefore, any oxidative attachment to these alloys should be expected to show selective attack on the chromium. Stainless steels, having more chromium than smdied Ni-based alloys for molten salt applications, are more susceptible to corrosion by fluoride melts, but can be considered for some applications. 

In this chapter we summarize the main features of the p>seudolattice theory of ionic fluids, starting with the experimental evidence of the existence of this kind of stmctmal arrangement in these systems. The so-called Bahe-Varela formalism of concentrated electrolyte solutions is reviewed, and its generalization to transpert phenomena introduced. On the other hand, the pseudolattice approach to equilibrium and transport properties of pure room temperature molten salts (ILs) and their mixtures with molecular fluids is analyzed. Particularly, pseudolattice theory is seen to provide an adequate understanding of both volumetric and surface properties of ionic liquid mixtures, as well as of electrical and thermal transport in these systems. 

When sodium chloride is dissolved in water at ordinary temperatures, it is practically completely dissociated into sodium and chloride ions which, under the action of an external field, move in opposite directions and independently of each other subject to coulombic interactions. If, however, sodium chloride is dissolved in a solvent of lower dielectric constant, and if the solution is sufficiently dilute, there is an equilibrium between ions and a coulombic compound of the two ions which are commonly termed 4 ion pairs. This equilibrium conforms to the law of mass action when the interaction of the ions with the surrounding ion atmosphere is taken into account. In solvents of very low dielectric constant, such as the hydrocarbons, sodium chloride is not soluble however, many quaternary ammonium salts are quite soluble, and their conductance has been measured. Here at very low concentrations, there also is an equilibrium between ions and ion pairs which conforms to the law of mass action but at higher concentration, in the neighborhood of 1 X 10 W, or below, a minimum occurs in the conductance. Thereafter, it may be shown that the conductance increases continuously up to the molten electrolyte, provided that a suitable electrolyte and solvent are employed which are miscible above the melting point of the electrolyte. 

Oxoacidic properties of oxo-compounds of chromium molybdenum in molten equimolar KN03-NaN03 mixture were studied by Kust [115], who used the standard potentiometric cell with a liquid junction. The measurement routine consisted in certain additions of neutral chromate or molybdate to the solution of the corresponding salt of composition Na2R207. Determination of the equilibrium O2- concentrations in these buffer solutions allowed the authors to estimate the equilibrium constants as... 

In molten fluoride-salt systems, the drivdng force for mass transfer is a result of a temperature dependence of the equilibrium constant for the reactioit Itetween chromium and IJF4 (Eq. 13-3). If nickel and iron are considered inert diluents for chromium in Inconel, the process can be simply described. I.hider rapid circulation, a uniform concentration of UF4, IT 4. and CrF2 is maintained throughout the fluid the concentrations must satisfy the equilil)rium constant... 

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