The mass transfer of phosphoric acid from a single water drop falling in a continunous phase of n-octanool and the related drop dynamics were studied experimentally. For the drops of low acid concentration the terminal velocity agreed well with the prediction of Klee and Treybal. But its deviation was increased with the increase in acid concentrtion. The mass transfer coefficient in the continuous phase was well represented by
Also it was found that the dispersed phase coefficient for the drops of high concentration is favorably predicted by the model based on the penetration theory.