Abstract
Hydrogen content and specimen elongation were measured as functions of reaction time during cathodic hydrogenation of nickel strip specimens of various thicknesses. In contrast to earlier work, the hydride appears to have a composition close to 
. The reaction follows the parabolic rate law. The relation between elongation and hydrogen content depends on specimen thickness in a manner which can be simply interpreted in terms of the elastic and plastic properties of the hydride and metal, together with a residual stress in the newly formed hydride about 105 psi.