We are offering phosphotungstic acid. Certificate of analysis material : phospho tungstic acid (tungstophoshoric acid) appearance : white fine crystals molecular wt : 2280 maximum impurities: insoluble matter : max 0.01 % chloride (cl) : max 0.01 % heavy metals (as pb) : max 0.005% iron (as fe) : max 0.003% nitrate : max 0.05% sulphate (as so4) : max 0.01% copper (cu) : max 0.001% all these tests are analyzed at our own laboratory. thanks with best regards.