Mass Transfer from a cavity containing an eddy to the main contacting flow was investigated by computer simulation and visualization experiments. The mass transfer between the cavity and the main contacting flow was affected mainly by the rotation of the eddy and correlated as Sh = 2.29 ×10^-5Re^2.18Sc^1.03AR^0.156 where AR is the aspect ratio ranging from 1 to 4. The Reynolds number was varied from 25 to 100 and the Schmidt number from 100 to 10000.