反应条件
sulfuric acid; sulfur dioxide; iron in sulfuric acid
byproducts: FeCl2; ore contains SiO2, Al2O3, Fe, As, Sb, Mo, Na, K, Cl, N2O5; dissolving in aq. H2SO4 and in hot concd. FeCl2 soln., filtration, cementation on Fe, CuCl electrolysis, liquor recirculated;