Rate constants and other properties are reported for photochemical reactions initiated by laser photolysis (248 nm) of S2O82-(aq) in acidic solutions containing Cl-(aq) at 297 +/- 2 K. The absorption spectra of SO4-.(aq) and Cl-2(-.)(aq) are measured and compared to literature values. Equilibrium constants and rate constants involving Cl-.(aq), Cl-2(-.)(aq), H2O, SO4-.(aq), and S2O82-(aq) are determined by analyzing the formation and decay of Cl-2(-.)(aq) and SO4-.(aq) in a self-consistent chemical mechanism. For the first time, the anticipated pH dependence is observed unambiguously in the pseudo-first-order decay rate constant of Cl-2(-.). The rate constants for the reactions Cl-.(aq) + Cl-2(-.)(aq) --> Cl-2(aq) + Cl-(aq) and Cl-2(-.)(aq) + Cl-2(-.)(aq) --> Cl-2(aq) + 2Cl(-)(aq) are determined; rate constants for the latter are measured as a function of temperature and ionic strength. In addition, the ionic strength dependence of the reaction SO4-.(aq) + Cl-(aq) --> SO42-(aq) + Cl-.(aq) is reported. Rate constants for the reactions of Cl-.(aq) and Cl-2(-.)(aq) with S2O82-(aq) are reported for the first time. The present and previous (when available) experimental results are generally in good agreement within the context of the comprehensive chemical mechanism for this system.