The model of stirred vessel mass transfer previously presented [1] has been amended to account for transfer in the core region. In addition to the two-region picture, a modified single region model, in which the return flow to the interface occurs in a region close to the vessel wall, is also described. Both the corrected two region and the single region models show good agreement with data from transfer cells with no separators at the interface. The recent data of LOOSEMORE and PROSSER [2], in which the interface was partially blocked, were also in reasonably good agreement with theory if transfer in the core region of the interface is included.
IN A recent study, the mass transfer behaviour of stirred vessel extractors was analysed by means of a simplified flow model [l] (hereafter designated as the two-region model) in which each phase was divided into two parts; the core region, which contained the liquid in the volume swept out by the stirrer, and an annular region between the core and the vessel walls. The flow in the core region was assumed to be adequately represented by that of a semi-infinite fluid revolving over a stationary surface. This type of flow is characterized by an axial velocity component directed away from the stationary surface (the interface). The annular region served to return fluid to the interface. Based upon the supposition that the core behaved as a semi-infinite medium as far as mass transfer (in addition to hydrodynamics) was concerned, it was predicted that no transfer would occur in this region. The burden of transferring solute from one phase to another was attributed solely to the annular region.
Recently, LOOSEMORE and PRCXSW [2] have shown experimentally that this last prediction is incorrect. By covering various portions of the interface with different combinations of annular rings and disks, they found, the core region to be as effective in the interphase transfer process as the annular region.
The purpose of the present study is to demonstrate that mass transfer in the core region can be accomodated within the theoretical model previously advanced; in fact, it was an error not to have included this contribution in the original treatment.