Ternary gas diffusion - in vitro studies

The purpose of these experiments was to compare diffusive gas movement in a two-gas system with that in a three-gas system. Gas mixtures of different compositions were placed initially on either side of a removable partition dividing a cylindrical lucite diffusion chamber, filled with 3 mm glass beads. This served to slow diffusion, minimize convective currents generated by removing the partition, and stabilize temperature within the chamber. In two-gas systems, after the partition was removed, oxygen equilibrated between the two parts of the chamber more rapidly in a helium environment than in a nitrogen environment, conforming with predictions based on binary gas laws. Results obtained with a three-gas system differed significantly from those obtained with the binary system. With 21% oxygen in belium initially in one half of the chamber and 21% oxygen in nitrogen in the other, PO2 rose transiently in the He-O2 side of the chamber. Qualitatively, similar results were obtained when the O2-N2 mixture was replaced by 100% nitrogen. Pressure in the system remained essentially constant. The possible mechanisms responsible for the PO2 rise were studied using a computer model of the system. This showed that movement of a given gas may be affected significantly by movement of other gases in the system. Hence, application of binary gas diffusion laws to systems containing more than two gases may lead to significant errors.