Flow of Nascent Hydrogen through Metals

Atoms of hydrogen may be generated by electrolysis or by chemical reaction at the metal surface. Some of the atoms of hydrogen thus liberated may leave the surface as molecules and others may enter the metal and diffuse through it. The possible sequence of processes is 

The possible variables in this type of diffusion include current density, temperature, the dimensions of the membranes, concentration of acid, time, and the concentration of added salts. Bodenstein(ii) considered that his results on the diffusion of hydrogen through iron obeyed the relation 

Borelius and Lindblom(62), however, showed that over a considerable range of current densities the relationship was 

The explanation that the rate of permeation can be expressed as P — kd and that the surface is not fully saturated at low-current densities is not more tenable than Smithells and Ransley s earlier explanation of the same facts for thermal diffusion (p. 171). The most satisfactory explanation is that advanced by Barrer (p. 174). 

The influence of temperature upon the permeation velocity of hydrogen through iron and through palladium (53) shows that the rate of flow rises exponentially with the temperature The slope of the curves log (permeability) against 1/T(T = K.) for the Hg-Fe system (Fig. 71) is the same at all current densities from 0-0075 to 0-045 amp./cm., and is very nearly that found for the thermal j)ermeability ( eiect. = caL/atom, 

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