✍ Scribed by W. van Dingenen; A. van Itterbeek
No coin nor oath required. For personal study only.
Measurements have been made on the adsorption on charcoal of D2 and H~ in the temperature regions 90-55°K and 20-17°K.
Between 90-55°K the adsorption of D, is found to be about 8% greater than that of H,. Between 20-17°K this difference has increased to about 15~/o. It seems to us that this difference must be explained by a difference in potential and kinetic properties between the two isotopes (a difference in diameter .being out of the question) and that the way to treat this problem is analogeous to that developed by K. S c h ~ f e r, when dealing with the van der Waals' attraction. (Z. phys. Chem., B. 36, 98, 1937).
Between 90-55°K the adsorption isotherms can be represented by a Freundlich equation, between 20-17°K by a Williams equation.
The results obtained cannot be brought into agreement with the potential theory of P o 1 a n y i.
From the data obtained for the adsorption isotherms the heat of adsorption was calculated at various temperatures as a function of the adsorbed quantity. From this it can be concluded that there is a constant difference between the heat of adsorption of" D~ and of H. the adsorption heat of D: being higher-than that of H= (about 180 cal.).
The measurements of the adsorption were extended as far as capillary condensation, enabling us to derive the structure curve of the charcoal from which, the surface tension of D= was, finally, computed. In this way we found: 20,36°K, 0.81 dyn/cm; 19. 05 ° , 1.11; 17.48 ° , 1.70.
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