Problem.---When an activated and previously evacuated specimen of cocoanut shell charcoal is exposed to an excess of a mixture of oxygen and nitrogen, the two gases are unequally adsorbed. It is desired to determine how the equilibrium pressure at constant volume depends upon the composition of the mixture; the ratio of the mass of gas to the mass of charcoal being the same in all cases.Results.---(1) There is a nearly linear relation between the logarithm of the equilibrium pressure and the per cent. of oxygen in the mixture. (2) The two gases in the mixture are not adsorbed independently. (3) A given volume either of a pure gas or of a mixture is less completely adsorbed if admitted at one time than if it is admitted in two portions, the second half being admitted after the adsorption of the first has reached equilibrium.