A reactor has been setup for the study of photochemical reactions. This apparatus consists of three parts: (1) a UV source, a Hg lamp; (2) the quartz cylindrical sample cell; and (3) a gas chromatograph, placed downstream for product detection. The lamp and cell are placed In a dark box to minimize excitation from the background. Gas is continuously flowed through the liquid in the sample cell, which is filled with the reagents and the photocatalyst, and the gas products are sampled via a six-way valve inserted downstream. Thermal conductivity and flame ionization detectors are available for the detection of most gases, including hydrogen and oxygen.