The organic solvent effect on phosphomolybdic acid and its analytical application

The ultraviolet spectra of phosphomolybdic acid in aqueous and mixed solvent systems were studied. The spectra are profoundly affected by the addition of organic solvents such as tetrahydrofuran, ethanol and their homologues and eventually exhibit an absorption maximum at 310 run. The formation of phosphomolybdic acid was found to be quantitative even with low concentrations of molybdate ions (ca. 10(-4)M) at pH about 3. By using these facts, a simple method for direct spectrophotometric determination of phosphate ion has been developed.