Tungsten trioxide is almost exclusively manufactured by calcination of APT under oxidising conditions (in air). WO3 is one of the most important, highly pure intermediates for the production of other tungsten compounds including tungsten metal powder. In the latter application, it was substituted to a large extent by tungsten blue oxide. Because of its bright yellow colour it is used as a pigment in oil and water colours. It is employed in a wide variety of catalysts, most recently for the control of air pollution and industrial hygiene (DeNOx).
Tungsten trioxide particles are pseudomorphous to APT; which means the particles have the same shape and size as the former APT crystals, but consist of very small WO3 grains. The yellow powder is packaged in sealed polyethylene-lined steel drums and individual packaging (20 to 50kg).