Problem.-By varying the heat treatment of a given specimen of cocoanut shell charcoal both the rate at which it adsorbs air and the total amount it can adsorb from a given small mass of air can be varied over a wide range. These variations are studied for the case in which the mass of air used is less than that required to saturate the charcoal. Activation.-An increase in the adsorptive power, "activation," is produced by repeated evacuations at 650° C, each evacuation being followed by an

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... ption of air at the temperature of liquid air. De-activation.-A decrease in the adsorptive power can be produced by increasing the evacuation temperature to between 8oo° and 900 0 C. Hypotheses.-Hypotheses advanced to explain these phenomena are discussed.