This work is an experimental and theoretical study of antimony speciation and the solubility of Sb2O5, Sb2O3 and. Sb-2(SO4)(3) at 298 K in aqueous sulphuric acid solutions (0 to 6 kmol/m(3)). A thermodynamic model was developed to quantify the solubility products and aqueous metal speciation. Main dissolved species were H3SbO3(aq) and H3SbO4(aq). The solubility of antimony increases with increasing solution acidity and with the presence of hydrogen peroxide in the solution. The following standard equilibrium constants at 298 K were obtained: Log K-(Sb2O5)(0) = 11.7+/-0.5, Log K-(Sb2O3)(0) = 32+/-1, and Log K-(Sb2(SO4)3)(0) = 55+/-2.