Main Features of Molten Salt Systems

The transition from the solid to the liquid state is so commonplace that ancient scholars tried to explain this phenomenon. The development of the natural sciences in the sixteenth and seventeenth centuries enabled its deeper understanding, especially in connection with the development of suitable methods for the measurement of volume and heat. The first experiments to apply thermodynamic principles to the melting process of substances arose approximately at the time of the formulation of the second law of thermodynamics, i.e. in the middle of the nineteenth century. 

From the general structural classification, the crystalline substances can be divided into four groups  

At melting, each group forms its own type of melt. Of course, melts having the features of two of these groups may also occur. For example, silicate melts belong to the network forming as well as to the ionic melts. 

The Structure of inorganic melts is, in spite of their relative simplicity, not completely understood. The earlier calculations and simple models of molten salts were built up rather on intuition. However, they were the necessary first step for more sophisticated approaches. 

The concept of complexing in molten salt mixtures is somewhat different from that for solutes in aqueous or organic solvents. In water solutions, every ion is separated from the other ions by the solvatation wrapping of water. Ions, simple or complex, are mutually influenced only by weak forces and each ion behaves independently. 

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