7 g of tungsten(VI) oxide is combined with 6 g of very fine magnesium powder, the mixture is placed in a steel crucible and it is heated with a bunsen burner until the mixture catches on fire. After the mixture has cooled down, the contents of the crucible are pulverized and poured into 200 mL of concentrated hydrochloric acid with stirring. The mixture is filtered after no more bubbling occurs, and the residue is boiled with 150 mL of concentrated hydrochloric acid for a few minutes. The mixture is filtered, washed with water and the residue is dried in a desiccator. The fine powder is pyrophoric.
WO3 + 3 Mg = W + 3 MgO
The pure metallic tungsten