Measurements of the adsorption on 5A molecular sieves have established that, at 1 atm and 24.0 °C, both systems, propane-carbon dioxide and propylene-carbon dioxide, form Ideal solution adsorbed phases. Total mass adsorbed ranges from 112 to 207 mg/g of sorbent for propane-carbon dioxide and from 130 to 207 mg/g of sorbent for propylene-carbon dioxide. © 1980, American Chemical Society. All rights reserved