Studies on the Extractive Behaviour of 12-Heteropoly Acids. Part II : Extraction of 12-Molybdophosphoric, 12-Tungstosilicic and 12-Molybdosilicic Acids

The extractive behaviour of 12-molybdophosphoric (H₃PMo₁₂O₄₀), 12-molybdosilicic (H₄SiMo₁₂O₄₀) and 12-tungstosilicic (H₄SiW₁₂O₄₀) acids into various organic solvents have been studied. The order of extraction of H₃PMo₁₂O₄₀ into oxygenated organic solvents is very similar to that of H₃PW₁₂O₄₀. The oxygenated organic solvents extract H₃PMo₁₂O₄₀ and H₃PW₁₂O₄₀ better than H₄SiM₁₂O₄₀ and H₄SiW₁₂O₄₀. Equilibria involved in the extraction process are discussed and the extraction constants have been calculated. Extraction data give support to the view that 12-heteropoly acids are extracted into oxygenated organic solvents in the form of solvated ion pairs. From 0·5. M LiCl solution, salts of the type LiH₂M₁₂O₄₀ and LiH₃M₁₂O₄₀ are extracted into the organic phase (where M = Mo or W).