Abstract: Thiosulphate ions present in gas purification liquors, particularly those employed for removing H.sub.2 S by washing with aqueous alkaline solutions of vanadium compounds and anthraquinone disulphonic acids, are decomposed to sulphide and hydroxyl ions by exposing the liquor to a hydrogen rich gas at elevated temperature e.g., 650.degree. C. The liquor may be evaporated and the solid residue subjected to decomposition. Any thiocyanate ions are hydrolyzed; it being necessary to mix steam with the hydrogen rich gas if a solid residue is being decomposed.

Abstract: The activity of the metal components of Stretford Redox Liquors can be maintained in the presence of complexing groups present in the organic redox agent by preparing the organic quinone component under acidic conditions in the presence of ferrous or ferric ions. The iron complexed quinone may be added to the metallic components under conditions to maintain the alkaninity of the mixed Liquor.