Solubility of ozone and kinetics of its decomposition in aqueous solutions of NaCl and NaCl + HCl have been investigated as functions of solution composition, electrolyte concentration, and temperature. A methodology has been developed, in which dissolved O-3 concentration was measured by a direct spectrophotometric technique by absorbance at 260 nm, with ozone decomposition in the sample and the presence of other substances also absorbing light at 260 nm being taken into account. For solutions with concentrations of Cl- 0-2 M and H+ 0-0.5 M, the solubility coefficient (L-O3) and Henry's law constant of ozone (K-H) have been determined in the temperature range 20-40 degrees C, as well as the kinetic order and apparent rate constants of O-3 decomposition (at 20 +/- 1 degrees C). Formulas have been obtained for calculating L-O3 and K-H for various values of temperature and electrolyte concentration. An equation is presented for computing the rate constant of ozone reaction with chloride ion in aqueous solution via the mechanism of oxygen atom transfer as a function of temperature and concentration of H+ ions.