Trace Oxygen Analysis for Liquid Hydrogen Production
An important preliminary to the liquefaction of hydrogen is the removal of impurities which might condense at the low temperatures and result in plugging of the liquefier. Of the usual impurities, oxygen is especially important because of the possibility of an explosive combination of a local accumulation of condensed oxygen with hydrogen. In the NBS-AEC Cryogenic Engineering Laboratory liquefaction plant, oxygen is removed by catalytic combination with the hydrogen, followed by freezing out of the resulting water. Two sensitive commercial oxygen analyzers of different types have been used to measure the residual oxygen which usually has a concentration of the order of 1 ppm or less. Unfortunately both respond to variations in the ortho-para composition of the hydrogen.