Magnesium reduction of WO_3 in a self-propagating high-temperature synthesis (SHS) process

High-purity tungsten was prepared by the self-propagating high-temperature synthesis (SHS) process from a mixture of WO 3 and Mg. The MgO in the product was leached with an HCl solution. The complete reduction of WO 3 required a 33% excess of magnesium over the stoichiometric molar ratio Mg/WO 3 of 3 . The product tungsten had a purity of 99.980% which was higher than that of the reactant WO 3 . This is because the impurities were either volatilized at the high temperatures generated during the rapid exothermic reaction or dissolved into the HCl solution during leaching.