The effect of temperature on the reaction kinetics of chlorine with basic hydrogen peroxide (BHP) was investigated for the system of Cl2 at atmospheric pressure absorbing into 4 M KOH in aqueous hydrogen peroxide for the temperature range of 0-20 °C. This reaction is important for the production of singlet delta oxygen [O1(1Δg)] used in the chemical oxygen-iodine laser (COIL). The kinetics experiments of Ruiz-Ibanez ana Sandall for Cl2diffusing and reacting in BHP in a laminar liquid jet absorber were modeled by material and energy balances which were solved numerically. Our results for the second-order rate constant were correlated for temperature dependence by the Arrhenius expression fe(m3/(kg-mol s)) = 1.2 X 1031 exp[-15800/T(K)]. These results show an order of magnitude increase for the rate constant over the approximation of Ruiz-Ibanez and Sandall due to the depressed solubility and diffusivity of Cl2 in BHP arising from ion effects in the liquid phase.