Bounds of Complex Formation for Alkali-Earth Cation in Molten Alkali Chlorides

Electrical Conductivity of (LiCl–KCl)eut.–SrCl2 Molten Mixtures

“…When SrCl 2 is added to the LiCl–KCl melt, the Sr 2+ cations with chlorine anions mainly form SrCl 4 2– complexes, ,,− which are somewhat stronger than Li + complexes. But since the difference in the ionic moments of Li + and Sr 2+ is small, strontium weakens the lithium complexes only slightly, and together they further reduce the mobility of the Cl – anions.…”

“…The experimental and theoretical studies of the structure of molten SrCl 2 showed that liquid strontium chloride does not form any stable complex structures like CdCl 2 (tetrahedron) or molten YCl 3 (octahedron), and the coordination number of Sr 2+ is 6.6–6.9. ,− When the first portions of LiCl–KCl are added to individual SrCl 2 , the specific conductivity increases due to the appearance of almost free K + cations (Figure ). But there are still many divalent Sr 2+ ions in the melt.…”

Partitioning of elements between silicate melt and immiscible fluoride, chloride, carbonate, phosphate and sulfate melts, with implications to the origin of natrocarbonatite

“…In the complex fluoride melts produced in our experiments, alkalis and alkaline earths interact with aluminofluoride complexes, while in chloride melts the smaller alkaline earth cations themselves form tetrahedral anionic complexes, e.g., [MgCl 4 ] 2À or [BeCl 4 ] 2À analogous to [AlF 4 ] 3À anions of fluoride melts (Sakai et al, 1984). The enhanced stability of 4-fold coordination relative to the 6-fold coordination for smaller divalent cations in chloride melts may be the reason for greater fractionation of large and small alkaline earths in chloride-silicate system (Fig.…”

Stability diagrams for fourfold coordination of polyvalent metal ions in molten mixtures of halide salts

“…The word "complex" has been used in the literaturewith somewhat different meanings by different authors. A strict viewpoint uses it to denote a kinetic entity persisting in the liquid over times appreciably longer than typical fi_nes for translational and rotational diffusion, i. e. longer than 10"11 s and possibly as long as 10-5 s. The same expression is still applied by some authors to systems in which polyvalent metal ions are fluctuating between fourfold-coordinated and more highly coordinated states over a time scale which is just sufficiently long for some characteristic structure to be visible in a Raman scattering spectrum, the time scale of the experiment being then of order 10"13 s. As an example of a borderline case of the latter type we may quote the CaC12.2KC1 mixture, as examined by Raman scattering and discussed in the work of Sakai, Nakamura, Umesaki and Iwamoto (1984). Data analysis has led the authors to propose coexistence of tetrahedral-type and octahedral-type coordinations for the Ca ion°One may expect in this case fairly rapid fluctuations for each Ca ion between the_e two preferred coordinations, given the good ionicity of the melt.…”