Analytical applications of β-heteropoly acids : Part I. Determination of arsenic,germanium and silicon

The existence of two forms of several heteropolymolybdates, differing in structure and stability, was confirmed. The unstable β-forms were stabilised by addition of comparatively large amounts of polar organic solvents, especially acetone, presumably because the solvent displaces water from the surface of the heteropoly anion and so inhibits any reorganisation of the structure of the anion. The organic solvent also intensifies the colour. The methods are rapid, sensitive, precise and accurate. Various applications are described.