Molten general assumptions

The model of Wilemski and co-workers [2, 3,26] is one of the first molten carbonate fuel-cell electrode models. Together with the models of Jewulsld and Suski [28,34], they form the basis for the class of thin-film electrode models (Figure 28.4). The following general assumptions are made in thin-film models ... 

Theoretical interpretation of the concentration dependence of equivalent conductivity for simple binary mixtures was first presented by Markov and Shumina (1956). It should be emphasized that this theory, even when considering simple structural aspects, represents rather a method of interpretation of the experimental data than a genuine picture of the structure of the melt. In molten salts generally only ions and not molecules are present, hence the conception of Markov and Shumina (1956) is to be considered also from this aspect. Their theory is based on the assumption that the electrical conductivity of a mixture of molten salts varies with temperature like pure components. In this respect, general character of the electrical conductivity dependence on composition, indicating the interaction of components in an ideal solution, could be expected. 

The assumption that the b axis is a linear function of the ionic proportions is quite obviously an empirical approximation, whose main virtues are that it is simple and gives reasonable cell dimensions generally. In fact, the average (Na, K)-0 distance does not increase linearly with the substitution of K" " for Na (Burnham and Radoslovich [1963]). Moreover, the elfect of K on the b axis of muscovite has been studied quite directly by Burns and White [1963]. They treated muscovite with molten lithium nitrate, thereby forcing Li ions into the vacant octahedral sites, reducing the layer charge, and removing the potassium. The b axis decreased, as expected, and the data indicated a curvilinear relationship with at least two distinct slope values between the b dimension and potassium content. 

---