A study has been made of the mercury photo‐sensitized decomposition of methyl chloride over a pressure range of 10 mm to 640 mm, a temperature range of 72°C to 328°C, and a threefold variation in light intensity. The stoichiochemical equation for the reaction at 250°C and 160‐mm pressure is3CH3Cl=HCl+0.97CH4+0.49C2H4Cl2+0.41Hg2Cl2+0.24C2H4+0.18CH2=CHCl+0.15C+0.07C2H6+0.02H2+0.01C2H2. At high pressures, the following mechanism is shown to be consistent with the experimental results:Hg(63P1)+CH3Cl=Hg(61S0)+CH3+ClCH3+CH3Cl=CH4+CH2ClCl+CH3Cl=HCl+CH2ClCH2Cl+CH2Cl=C2H4Cl2Hg+CH2Cl=HgCl+CH2HgCl+HgCl =Hg2Cl2CH2+CH2 =C2H4The first of these reactions is shown to have a quantum efficiency of unity. From the effect of added CO2on the reaction, an approximate value of &sgr;2=5.7×10−16cm2has been calculated for the quenching cross section of methyl chloride.
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