The formation of molybdosilicic acids from mixed solutions of molybdate and silicate

Abstract

A fundamental re-appraisal of the conditions leading to the formation of α- and β-molybdosilicic acids has been made. The classification of these conditions recommended by Strickland has been rejected and replaced with the rigorous system involving pH and molybdate concentration in the reaction mixtures. The α-molybdosilicic acid is formed at pH between 3·8 and 4·8 (possibly slightly higher) and the β-acid at pH between 1·0 and 1·8. The yield of both α- and β-acids (at pH 4·0 and 1·2) is independent of molybdate concentrations between 0·015 and 0·100 mol l^–1. The rate of formation of each compound at various known pH and molybdate concentrations is discussed. A number of hitherto unexplained complications reported by other workers are now resolved.