Composition: H₂WO₄ (often hydrated) CAS: 7783-03-1 EC No.: 231-975-2 M (Molar Mass): 249.86 g/mol (monohydrate) Appearance: Yellow crystalline powder.

Assay (as WO₃, after ignition): ≥ 99.0 % Appearance: Yellow powder. Insoluble Matter (in NH₄OH): ≤ 0.05 % Loss on Ignition (to WO₃): 7.0 - 9.0 % (theoretical for H₂WO₄ is 7.2%) Chloride (Cl): ≤ 0.01 % Sulfate (SO₄): ≤ 0.02 % Nitrate (NO₃): ≤ 0.005 % Heavy Metals (as Pb): ≤ 0.005 % Molybdenum (Mo): ≤ 0.05 %