AbstractA dye tracer technique was utilized to measure the residence time distribution of the drops in a spray column, operating with a dispersed or a dense packing of drops, for a wide range of flow rates, in a 15 cm.in diameter, 150 to 160 cm. long column proper.For dispersed packing of drops and for flow rates below the onset of coalescence, the flow of the drops was approximately plug flow, with a variance of the residence time distribution of 0.095. For flow rates above the onset of coalescence within the column, the variance increased sharply to 0.55 and decreased at higher flow rates.For dense packing of drops the variance of the residence time distribution was in the range of 0.1 to 0.5. This variance is attributed to the effect of bypassing water and kerosene near the wall of the column. A mathematical model based on this effect showed reasonable fit with the experimental results. This model predicts an approach to plug flow of the drops for large diameter columns.