Abstract: After we succeeded in preparing white powdery tungstic acid hitherto not described in literature, we have found that on account of its reactivity, different from tungstic acid in yellow form, white powdery tungstic acid can be well used for preparing a variety of compounds including different kinds of salts of meta-tungstic acid as well as certain heteropoly tungstic acid and their salts.Ammonium metatungstate, AMT, prepared by neutralizing white powdery tungstic acid with ammonium bicarbonate gives a perfectly clear, rather concentrated solution, then well defined crystals at room temperature. Although the crystals thus prepared rather readily lose part of water of hydration, as revealed in thermal analysis, we have succeeded in measuring its X-ray diffraction pattern not yet revealed in literature. The diffraction pattern of AMTcrystal has been found as a =18.08Å, Z = 4. The molecular formula of AMTcan be expressed as (NH₄)₆[H₂(W₃O₁₀)₄]·20H₂O.