Abstract
Electron diffraction was used to measure the rate of the reaction between copper and pure dry oxygen at room temperature and 20 mm. pressure. The experimental technic is described in detail. The empirical rate of reaction is found to be inversely proportional to (
) for the time 
greater than two minutes; the constant 
is experimentally indistinguishable from zero but must be finite. It is estimated that the local thickness, 
, in Ångstrom units of the oxide film increases according to the equation: 
where 
is measured in minutes and is greater than 2 min. A limiting film thickness of about 50 Å is predicted by this equation.