Microanalysis of Gas in Cathode Coating Assemblies

A study of gases evolved from oxide-coated cathode assemblies was made during degassing and activation conditions. It was found, first, that the volume and nature of gases evolved from uncoated nickel cathode sleeves were practically independent of the three different cleaning methods used; and, second, that hydrogen-fired cathodes liberated slightly larger quantities of hydrogen when heated in vacuum. The release of hydrogen from nickel cathodes was not instantaneous, but was observed to continue even after two and one-half hours of continued heating at 900° C. Br. When a similar analysis was made of gases liberated from nickel sleeves coated with alkaline earth carbonates, the evolution of hydrogen was reduced considerably, but with a corresponding increase of CO. The chemistry of the gas condition in the tubes during cathode degassing is shown to be related to the speed of exhaust.