Although many studies have been made showing that surfactants can lower gas absorption rates the mechanism by which this occurs is not known. The purpose of the investigation was to show what effect the hydrophilic functional group has on gas absorption rates. Four different biodegradable surfactants were used. All four are used in commercial formulations. All four surfactants also had a linear hydrophobic group of 12 carbon atoms. In addition the position of the hydrophilic functional group was studied using 1-octanol and 4-octanol. Pure surfactants were used so that the interfacial resistance could be related to the surface concentration by means of Gibbs' adsorption isotherm. A quiescent liquid manometric gas absorption cell was used for the study. Carbon dioxide and water were used as the absorption system. Dodecyl sodium sulfate, dodecyl benzene sodium sulfonate, dodecyl diethanol amide and dodecyl diglycol amide were the four surfactants studied with different hydrophilic groups. The interfacial absorption resistance caused by the surfactant decreased with increasing molecular weight of the hydrophilic portion of the molecule. The interfacial resistance increased as the hydrophilic group moved from the end toward the center of the linear alkyl hydrophobic chain. (Author)