A Servomechanism Detector for the Quantitative Measurement of Gas-Chromatographic Zones of Hydrogenatable Material

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Abstract
Gas from the column joins a secondary stream of gas carrying electrolytically generated hydrogen. The combined stream passes through a reactor of hydrogenation catalyst to an electrochemical cell which is sensitive to hydrogen but not to products of hydrogenation. The output of the cell is applied to an amplifier which controls the supply of electricity to the hydrogen generator so as to form part of a feedback loop. In the steady state in the absence of vapor, the amplifier is adjusted so that there is a steady small generation of hydrogen, thus giving at the cell a concentration of hydrogen held steady by the servomechanism. When a vapor appears, there is a momentary fall in the concentration of hydrogen at the cell due to reaction in the reactor, and this is compensated by the servomechanism, which increases the hydrogen generation. As the peak is eluted, the servomechanism causes extra hydrogen to be generated which is exactly equivalent to the vapor according to the hydrogenation reaction. Thus, the peak in hydrogen generation gives an absolute measure of the quantity of the vapor. The use of the apparatus for measurement of oxygen and alkenes is described. A modification is its use for the physico-chemical study of dehydrogenation reactions and catalysts.

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