Quantitative experiments to establish the isothermals of adsorption on nonporous surfaces have only rarely been undertaken, owing mainly, no doubt, to the obvious difficulty of measuring the small absolute adsorptions on surfaces of manageable size. Yet it can well be held that many, if not all, of the uncertainties still attaching to the mechanism of adsorption and the constitution of the adsorption layer depend not upon any inherent complexity in the process itself, but upon the complicated geometrical and chemical conditions existing in the accessible surfaces of the porous materials, such as charcoal, that have so often been the subject of study. Moreover, it is by no means easy to determine in many cases what parts of the total “sorption” are due to adsorption, solid solution, or even chemical combination. McBain has emphasised the sensitiveness of the course of adsorption to the progressive removal of chemical heterogeneity from a porous surface. Some applications of the electric coherer to adsorption problems have been described in former communications; it may perhaps be appropriate to recall the main advantages that the method appears to possess over the more direct technique in common use; (
a
) the adsorption takes place on the non-porous and chemically homogeneous surface of a fine metal filament, that can be submitted to heat treatment electrically with great ease; (
b
) there is an immediate and direct test of the “bareness” of the surface, quite independently of the subsequent adsorption experiments; (
c
) from the nature of the technique only true surface films play any part in the measurements. The principal disadvantage is that the adsorbed amount is measured by the critical cohering voltage instead of directly, but this difficulty can be surmounted in the following way.
Production of Metal Filament by In-Rotating-Water Spinning Method
