The influence of magnesium and aluminum salts as impurities on the hydrolysis of titanyl sulfate was investigated. The degree of TiOSO_4 conversion to hydrated titanium dioxide (HTD) and the particle size of HTD were measured as functions of the concentrations of MgSO_4 and Al_2(SO_4)_3 in the TiOSO_4 solution. The Boltzmann growth model, which focuses on two main parameters, namely the concentrations of Mg~(2+) and Al~(3+) (ρ(Mg~(2+)) and ρ(Al~(3+)), respectively), fits the data from the hydrolysis process well with R2>0.988. The samples were characterized by ICP, SEM, XRD, and laser particle size analyzer. It is found that the addition of MgSO_4 simultaneously improves the hydrolysis ratio and the hydrolysis rate, especially when F (the mass ratio of H_2SO_4 to TiO_2) is high, hydrolysis ratio increases from 42.8% to 83.0%, whereas the addition of Al2(SO_4)_3 has negligible effect on the chemical kinetics of HTD precipitation during the hydrolysis process, hydrolysis ratio increases from 42.8% to 51.9%. An investigation on the particle size of HTD reveals that the addition of MgSO_4 and Al2(SO_4)_3 clearly increases the size of the crystallites and decreases the size of the aggregates
