An equipment used for measuring the evolution of gas is described in this paper. The equipment can be used for various kinds of materials

whether metallic or nonmetallic

magnetic or non-magnetic. Considerable amount of data for 1X18H9T （non-magnetic stainless steel） was obtained and it was shown that this proves to be a good material to be used in vacuum technique

that electrolytic etching is a suitable process to be adopted and that the formation of oxide film will result in an increase of gas evolution which should be avoided. The solution of the diffusion equation is also discussed. The critical point lying between the "semi-infinitive" and the "thin sheet" is given. A method used for determining the diffusion constant by means of a universal curve is mentioned. Finally

a method of treatment is proposed for the case where the diffusion constant varies with time.