Isotherms for the adsorption of ethane, propane, dimethyl ether and diethyl ether by activated charcoal were obtained at temperatures from 0° to 183° and at pressures varying from less than l mm. to about 1 atm. With the hydrocarbons equilibrium was attainable only after long periods of time. The isotherms for the hydrocarbons are in general almost rectilinear; those for the ethers have the usual form. At low temperatures the isotherms for the hydrocarbons show a peculiar type of break in the curve. The amount of vapor adsorbed decreases with an increase in the complexity of the adsorbed molecules. Semi-log isotherms, double-log isotherms, isobars and isosteres were calculated from the natural isotherms. The heat of adsorption was calculated from the slope of the isosteres
