In an earlier paper (11), the continuous-phase mass transfer coefficients resulting from the continuous-flow contact of ethyl acetate and water in an agitated vessel, ethyl acetate dispersed, were reported to be substantially larger than might be expected from consideration of the data obtained from solid particles in agitated liquids. The enhancement of the mass transfer coefficients was attributed to coalescence and redispersion of the drops of were thrown radially from the im-ethyl acetate peller and circulate to the top and bottom of the vessel, eventually around again to the impeller. It was reasoned that coalescence and redispersion, both fairly violent processes, interfered with and destroyed the buildup of ;I steady state concentration gradient in the liquid surrounding the drops, and it was shown mathematically that this could substantially increase the time-average coefficients. For baffled vessels it was found possible to describe thew coefficients reasonably well by the expression as where k,, a steady state coefficient, was estimated from the data for suspended solid particles of the same size as the drops ( 2 ) , and Oc represents the time between coalescences and redispersions. The latter was estimated for lack of a better means from observation of the change in mean drop size from the level in the vessel just opposite the impeller to that at the top and bottom:
1
The circulation time was estimated for the baffled vessels from the work of Holmes ( 3 ) . The second term on the right of Equation (1) represents the enhancement of the mass transfer rate resulting from the relatively violent coalescence phenomenon; the constant 3.94 is empirical, chosen to fit the data best. The coefficients for the vessel without baffles, operated without an air-liquid interface and therefore without a vortex, were appreciably larger at the same impeller power, but lack of information on the circulation times in such vessels prevented inclusion of these data in the correlation represented by Equation ( 1).