“…Depending on the particular reaction conditions, chlorination takes place in addition to sulfochlorination. The ratio of chlorination to sulfochlorination decreases with an increase in light intensity (up to an "optimal value"), shorter wave lengths, an increase of the S02/C12 ratio in the feed gas (up to a ratio of 1.3/1), a decrease in temperature, and a reduction in bubble size (14). Certain catalysts capable of generating free radicals, such as peroxides (8) and tetraethyllead, can be substituted for light.…”