The Diffusion of Hydrogen Through Oxygen-Free Copper

Abstract

A precise determination has been made of the diffusion of hydrogen through copper that is spectroscopically oxygen‐free. The range of temperatures is from 450°C to 1050°C. The copper appears perfectly homogeneous over the entire range, the equation followed being $$\mathrm{Rate}{\mathrm{=Ap}}^y{T}^z{e}^{\mathrm{-b/T}},$$ where p is pressure, T absolute temperature, A and b constants characteristics of copper. The value of z is about +0.5±0.2 as was found in pure nickel. The principle point to be noted is that y=0.50±0.01 even at 450°C. It is well known that copper containing any appreciable amount of oxygen shows isotherms in this region with a value of y as large as 0.8 in some instances, when log R is plotted against log p. When this same copper diffusor is slightly charged with oxygen the value of y becomes greater than 0.5, except at high temperatures. However, when isotherms are plotted log rate against log pressure, the result is a perfectly straight line in all cases. It now appears that the removal of all traces of oxygen from copper has the same effect on low temperature hydrogen diffusion isotherms as the removal of all carbon from iron and nickel, viz., these isotherms become perfectly normal, the rate varying exactly as the square root of the pressure.