RADIOLYSIS OF HCOOH + O2 AT PH 1.3-13 AND YIELDS OF PRIMARY PRODUCTS IN GAMMA RADIOLYSIS OF WATER

The radiation yields of carbon dioxide, hydrogen peroxide, and hydrogen from oxygenated ([O2] = 1 × 10-3 M) aqueous formic acid solutions have been determined over the pH range 1.3 to 13. The formic acid concentration was varied between 1 × 10-4 and 5 × 10-2 M and the absorbed doses ranged from 3 to 16 krads. The radiation chemical behavior of solutes is discussed paying particular attention to secondary reactions which may influence the measured initial yields of radiolytic products. Since these yields depend on solute reactivity they were corrected, before employing them to calculate the primary yields, using the Flanders-Fricke method and Kuppermann's diffusion-kinetic theoretical curves. The contribution of the reaction HCOO- + H to the measured yields of CO2 and H2 has also been taken into account. From the results obtained, one can calculate at pH between 3 and 13: G-H2O = 4.09, GH + Geaq- = 3.18, GOH = 2.72, GH2, = 0.45, and GH2O2 = 0.68. The increase in acidity induces an increase in water decomposition. At pH 1.3 the following values were derived: G-H2O = 4.36, GH + Geaq- = 3.49, GOH = 2.85, GH2, = 0.43, and GH2O2 = 0.76. These figures are discussed in the light of some uncertainties in corrections applied to measured values, as well as in reactions of formate ion at pH 12-13.