Volatilities of the Saturated Vapor Components of UCl4–RbCl Molten Mixtures

For the first time, the volatilities of UCl4 and RbCl from their molten mixtures containing 2.0, 5.0, 12.3, 25.2, 32.6, and 48.8 mol % UCl4 are measured in the temperature range from 890 to 1200 K using the transpiration technique. The chemical composition of the saturated vapors is determined. The commensurable amounts of binary compounds with the presumably RbUCl5 composition are found to be present in the vapor phase along with UCl4 and RbCl monomers and Rb2Cl2 dimers. The variation of the temperature and concentration of the UCl4–RbCl molten mixtures with significant negative deviations from ideal behavior can change the volatility of uranium tetrachloride by several orders of magnitude. The laws of changing the volatility of uranium tetrachloride from its molten mixtures with various alkaline metal chlorides are discussed. The experimental data obtained by us earlier and in this work indicate that, in the medium of molten alkaline metal chlorides, the U4+ ions enter the composition of complex anionic groups, the strength of which increases with a decrease in the uranium ion concentration in solutions and a decrease in the counterpolarizing effect of the alkaline cations on the anionic groups on going from LiCl to CsCl. This leads to a decrease in the volatility of UCl4 in the same direction. An almost linear change in $$\log {{f}_{{{\text{UC}}{{{\text{l}}}_{{\text{4}}}}}}}$$ as a function of the inverse radius (ionic moment) of the alkaline cations is observed.