AbstractThe interphase rate process for the extraction of mercaptan sulfur from n‐pentane with a 10% caustic solution is examined. The system represents a case of mass transfer with an equilibrium chemical reaction occurring in one phase. Experimental studies were made with both a continuous flow stirred tank reactor (CFSTR) and an annular flow jet reactor (AFJR). The interphase volumetric mass transfer coefficient (KLa) was derived based on Olander's theory. The KLa data for each contactor was found to be a function of the power input per unit volume. The AFJR exhibited higher KLa values and equilibration of mercaptan sulfur was achieved in about three millisecond