Magnesium reduction of WO₃ 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 WO₃ and Mg. The MgO in the product was leached with an HCl solution. The complete reduction of WO₃ required a 33% excess of magnesium over the stoichiometric molar ratio Mg/WO₃ of ₃. The product tungsten had a purity of 99.980% which was higher than that of the reactant WO₃. 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.