Abstract: A method and apparatus for producing pre metallic oxides by dissolving the metal or oxide in heated dilute hydrochloric acid to form metallic chloride in a water solution (which solution may instead, be a waste product from a steel strip pickling line), reacting said solution in a reactor in the presence of heated oxygen to form metal oxide, part of which oxide being carried over in vapor form to a variable throat venturi where it is redissolved and reintroduced into the reactor to insure that only low chloride oxide will be discharged as a product. The system operates under negative pressure to prevent leakage tendency of HCl to the outside atmosphere.