A review is presented of various types of solutions of metals in molten salts, especially in their own molten halides. With relatively little reference to the older literature, the progress made in the last 20 years is discussed. Roughly, the solutions are classified into two groups: The metal may retain, to some degree, its metallic properties in the solution, or it may lose them through strong interaction with the salt solvent. The alkali-metal systems are typical examples of the former type, while solutions of cadmium or bismuth represent the second. Equilibrium phase diagram data are presented in detail for many metal- salt systems. These include critical solution temperatures, that is, temperatures above which metal and salt are miscible in all proportions. Electrical conductivity is singled out as a most significant physical property from which conclusions on the state of the electron in the solution may be drawn. In the electronically conducting solutions, notably of the alkali metals, the electrons may be thought to resemble F centers in color-center colored crystals. In solutions where electronic conductance is absent, monomeric, dimeric, and even more highly poly, merized species of the solute metal in a low valence state must be assumed to occur. (auth)
