THE EFFECT OF PHYSICAL ADSORPTION ON THE ELECTRICAL RESISTANCE OF ACTIVE CARBON

Abstract

The change of the electrical resistance of active carbon rods due to the reversible adsorption of vapors is described. The effects of six saturated hydrocarbons and ethyl chloride were studied. An interesting regularity in the results obtained with the hydrocarbons was found, namely that the extent of the resistance change at a given temperature and volume adsorbed is proportional to the number of carbon atoms in the adsorbate molecule. The alteration of the electrical conductivity of the active carbon by the physically adsorbed vapors and the adsorption isotherms are not modified by small quantities of chemisorbed oxygen. Ethyl chloride exhibits a more complex behavior than the hydrocarbons. It is argued that the resistance measurements may be utilized to support the viewpoint that physically adsorbed saturated hydrocarbon molecules tend to lie flat on the adsorbent surface. Several possible explanations of the findings are examined and proved to be inadequate.