The rates of thermal decomposition of seven kinds of oil in a evacuating system under the operating condition similan to that of glass diffusion pump were measured at the neighbourhood of their operating temperatures.
The rate of the evolution of decomposed gases in represented as the rate of flow (S×Δp) which is the product of the pumping sheed and the pressure rise degree in the ionization gauge.
It was proved that the rate of decomposition and its initiation owed the small concentration of unstable substance in the oils. This conclusion agrees to the previons discussion* in the ultimate pressure of oil diffusuion pump.
