Permeation Devices for High Pressure Gases

Permeation tubes have been used as a convenient, standard gas source. However, they have the disadvantage of producing only one concentration of the gas under constant conditions. In addition, they have a limited lifetime and each new tube must be calibrated before use. This work describes a permeation device which can be used for gases which have liquifaction pressures too high for construction of permeation tubes. Plots of gas pressure vs. final concentration and concentration vs. equilibration time will be presented, as well as studies of the effect of temperature variations and Teflon length on permeation rate. Other advantages to these devices will be discussed.