HENRYS LAW CONSTANT AND HYDROLYSIS OF PEROXYACETYL NITRATE (PAN)

The effect of temperature on the solubility of PAN and on its hydrolysis rate in near-neutral and slightly acidic water were studied in a bubble column apparatus. The results obtained are a Henry's law coefficient H = 10(-9.04 +/- 0.6) exp[(6513 +/- 376)/T] M atm-1, and a first-order hydrolysis rate constant k = 10(6.60 +/- 1.0) exp[(-6612 +/- 662)/T] s-1, which was independent of pH in the range 3.2 less-than-or-equal-to pH less-than-or-equal-to 6.7. The products formed are nitrite and nitrate in approximately equal proportions under near-neutral conditions. At a pH < 4, nitrite is oxidized in a secondary reaction, and nitrate becomes the only product at low pH. Previously measured deposition velocities of PAN on stagnant water surfaces are shown to be hydrolysis rate limited.