In this study, a calculation procedure of gas/liquid mass transfer capacity coefficients based on liquid/ liquid ones was developed and cold model studies on benzoic acid transfer between water and liquid paraffin, and oxygen transfer among water, liquid paraffin and air was carried out under various top/bottom blowing rates and liquid/liquid volume ratios. The liquid/liquid mass transfer rate increased with the increase in a top blowing rate, but the increasing rate of a larger vessel diameter to the top blowing rate was lower than that of a smaller one. The gas/liquid mass transfer rate increased with the increase in both of top and bottom blowing rates, but the difference became reduced with the increase in the top blowing rate. The bottom blowing rate to minimize the sum of the top and bottom gas flow rates was almost constant for a given gas/liquid or liquid/liquid mass transfer rate. The liquid/liquid mass transfer rate increased and the gas/liquid one decreased with the increase in liquid paraffin volume ratio to water. There was a roughly positive correlation between the liquid/liquid and gas/liquid mass transfer rates throughout a wide range of top and bottom blowing rates, but the tendency was the opposite under the condition of the same paraffin volume and total blowing rate.KEY WORDS: liquid/liquid mass transfer; gas/liquid mass transfer; top/bottom blowing converter.