The purpose of this investigation was to determine meaningful values of interfacial area and contact time for mass transfer on a sieve-tray. These values were determined by measuring the rates of absorption of carbon dioxide into aqueous solutions and forcing the parameters to give answers consistent with the rates of absorption. These values were checked by comparing the interfacial area determinations with independent measurements. The interfacial areas and contact times were determined for liquid :eed rates of 10, 20, and 30 cubic centimeters per minute; slot velocities of 22, 26, 30, and 34 feet per second; hole diameters of 1/8, 1/4, and 3/8 inches; tray thicknesses of 1/16, 1/8, and 1/2 inches; free areas of 1.56, 3.52, and 7.04 percent; and depth of unaerated liquid or the tray of 1.00, 2.00, and 3.00 inches. The values of the interfacial area determined in this investigation were consistent with independent, previously measured values. The values of the contact times determined were about four times greater than previous estimations; this discrepancy was attributed to wall effects and differences in froth characteristics. / Ph. D.