Coulometric determination of chloride which is photolytically generated from trichloroacetic acid (TCA) is used for actinometry. Silver (I) is coulometrically generated from a silver anode and the change in chloride ion concentration is monitored potentiometrically. Photolysis - coulometry coupling yields a linear relationship between time of photolysis of solutions of TCA and the microequivalents of electrons required for titration back to the initial solution potential. If the recommended procedure is followed, errors about ten times those found for titration of standard chloride solutions are obtained.