An apparatus constructed for measuring permeation properties of polymer membranes using a mixture of gases is described. A gas chromatographic system was applied to determine the individual transport characteristics of component gases without a vacuum line. This paper also discusses some experimental factors effecting the precision of measurement. The results show that there is a linear relationship between the permeation time and the volume of the gas permeated through the membrane within certain permeation period

which depends on the permeation rate(from 10-10 to 10-7 cm3(STP)/cm2.sec.cmHg) of the membrane.The reproducibility has been found to be good with a relative standard deviation of 3.5%.This method is more sensitive

considerably faster and more convenient for determining both the permeability coefficient and the separation factor of a polymer membrane from a chromat ogram using mixed penetrant gases.