The oxidation of nitrogen oxides in ceric solution was accomplished by the liquid-phase oxidation of nitrous acid. Kinetic measurements in a discontinuous reactor were performed using two analytical techniques. In particular, amperometric titration of Ce(IV) allowed on-line measurement of Ce(IV) concentration. The oxidation was shown to be a first-order process with respect to both Ce(IV) and nitrous acid, in the range 0.1-0.5 mol m-3. The concentration of sulfuric acid exerted a strong influence on the rate constant k in the range 500-9500 mol M-3. The presence of nitric acid resulted in additional reduction in k, especially for concentrated sulfuric solutions. The strong variation of the rate constant with the concentration of both acids is likely due to changes in the chemical states of nitrous acid in the solution. A factorial design method yielded the dependence of acid concentrations on the rate constant k=-0.0061+(144/[H2SO4])-[(3.03X10(-6))[HNO3]]+[(1.08X10(4))/[H2SO4]2] -[0.0041([HNO3]/[H2SO4])] m3 mol-1 s-1 at 25-degrees-C, for the concentration ranges at H2SO4, 500-5000 mol m-3, and HNO3, 0-4000 Mol M-3.