The reaction between roasted zinc blast-furnace dust (131713) and ammonium sulfate was studied in the temperature range 250-450degreesC using different molar ratios to determine the maximum extraction of zinc. The reaction products are characterized. The composition of the untreated and roasted BFD, and reaction products was investigated by chemical, thermal, X-ray diffraction and fluorescence analyses. The decomposition of ammonium sulfate leads to the formation of (NH4)(2)S2O7, NH4HSO4 and (NH4)(3)H(SO4)(3). The main zinc reaction products are ZnSO4, ZnSO3, (NH4)(2)Zn(SO4)(2), (NH4)(2)Zn-2(SO4)(3) and (NH4)(2)Zn-4(SO4)(5). The reaction mechanisms of these formations are discussed. in detail. The identity of these products depends essentially on the temperature as well as the molar ratios of the reactants. The optimum conditions for the formation of soluble zinc compounds are molar ratio L:8 of roasted zinc dust (ZnO) and (NH4)(2)SO4 at 350degreesC. Under these conditions, up to 95% of zinc was leached with 0.5 m sulfuric acid. (C) 2004 Society of Chemical Industry.