The sulfate method was first implemented industrially in 1931 for producing the anatase form of titanium dioxide, followed by the rutile form in 1941. This process involves dissolving ilmenite concentrate or titanium slag in sulfuric acid to create solutions of titanium, iron, and other metal sulfates. Through a series of controlled technological steps—including chemical reduction, purification, precipitation, washing, and calcination—basic TiO2 with the desired particle size is formed. The crystal structure (anatase or rutile) is determined during nucleation and calcination.