Rate of the reaction OH + OH → H2O + O

New measurements are reported on the rate constant for $\mathrm{OH}+\mathrm{OH}\to {\mathrm{H}}_2\mathrm{O}+\mathrm{O}{\mathrm{(k}}_2)$ at room temperature. The study was made with a fast flow reactor using a fixed ESR detector and a movable NO₂ injector for generating OH by the H + NO₂ reaction. Careful attention was paid to accounting for the effect of OH loss on the walls and of the overall stoichiometry at varying H/NO₂ ratios. A large number of runs with both H excess and stoichiometric H/NO₂ ratios gave $k_2{\text{= 1.4 ± 0.2 × 10}}^{12}{\mathrm{cm}}^3{\mathrm{mole}}^{\text{−1}}·{\sec }^{\text{−1}}$ .