Thorium valency in molten alkali halides in equilibrium with metallic thorium

✍ Scribed by M.V. Smirnov; V.Ya. Kudyakov

• Publisher: Elsevier Science
• Year: 1983
• Tongue: English
• Weight: 941 KB
• Volume: 28
• Category: Article
• ISSN: 0013-4686
• DOI: 10.1016/0013-4686(83)85187-1

✦ Synopsis

Metallic thorium is shown to corrode in molten alkali halides even in the absence of external oxidizing agents, alkali cations acting as oxidizing agents. Its corrosion rate grows in the series of alkali chlorides from LiCl to CsCl at constant temperature. Substituting halide anions for one another exerts a smaller infhumce, the rate rising slightly in going from chlorides to bromides and iodides, having the same alkali cations. Thorium valency is determined coulometrically, the metal being dissolved anodically in molten alkali halides and their mixtures. In fluoride melts it is equal to 4 but in chloride, bromideand iodide ones, as a rule, it has non-integral values between 4 and 2 which diminish aa the temperature is raised, as the thorium concentration is lowered, as the radii of alkali cations decrease and those of halide anions increase. The @of cellsThlNThHl,+(I -N)MHIIMHfIC,HI, 'f' whereHIisCl,BrorI,MisLi,Na,K,CsorNa+K,andN -z 0.05, is measured as a function of conamtra Ion at several temperatures. Expressions are obtained for its concentration depcndencc. The en$grows in the series of alkali chlorides from LiCl to C&l, other conditions h&g equal. A method is suggested for finding predominant pairs of ThHI,, ThHI, and ThHI, in chloride, bromide and iodide melts that are in equilibrium with metallic thorium. From experimental data, ThiW, and TkHI, are ascertained to prevail over ThHI,. Equations are derived for temperature dependence of conditional equilibrium constants for disproportipnation reactions of ThCl, in UCl, NaC1, NaCl+ KC1 and CsCl, ThBr, in NaBr +KBr, and ThI, in NaI +KI.