THERMOCHEMICAL AND STRUCTURAL INVESTIGATIONS ON ALKALI-METAL CHLORIDES-IRON(III) CHLORIDE SYSTEMS

The pseudobinary systems ACl-FeCl3 (A=Na, K, Rb, Cs) were reinvestigated by means of differential thermal analysis and X-ray powder diffraction. The existence of the compounds AFeCl(4) (A = Na-Cs) and Cs3Fe2Cl9 could be confirmed; Cs3Fe2Cl9 is a stable compound which decomposes to CsCl and CsFeCl4 above 270 degrees C. Additionally, two Rb-compounds - Rb3FeCl6 and Rb3Fe2Cl9 - were found, which decompose, when heated, in the solid state. Rb3Fe2Cl9 is isotypic with the analogous Cs-compound; Rb3FeCl6 has the Cs3BiCl6 structure. Cs3FeCl6 is isotypic with Cs3CrCl6, a recently found orthorhombic variant of the elpasolite type.