When a series of closely spaced gas bubbles flows with the surrounding liquid in a small tube, the. gas velocity will be greater than that of the liquid due to the thin stationary liquid film along the tube walls. This velocity separation meets a prime requirement for a chromatographic system. If a pulse of radioactive tracers is injected into such a system, the retention time of each tracer component will depend only on the gas and the liquid velocities, the relative amounts of liquid and vapor in the column, and the vapor-liquid equilibrium K value of the component. Thus, a bubble column can be used to determine K values. This work determined the K value of ethane at 74 °F and one atmosphere at infinite dilution in the helium-n-decane system to be 26.6 ± 2.1. This compares favorably with data taken by static means. The peak dispersion coefficient increased with the square of the bubble velocity. The film thickness vs. velocity agreed well with theory. The method has been extended in theory to the general case of n components with each component present in both phases.