Mass transfer studies in an agitated vessel

A study of rates of dissolution of organic solid from a flat surface into turbulent liquid in a mixing tank of 6 in. I.D. is reported for five systems—benzoic acid– n ‐water, salicylic acid–water, salicylic acid–benzene, succinic acid– n ‐butanol, and succinic acid–acetone. Previous theories for the rates of mass transfer are reviewed and compared, and experimental results analyzed and correlated by an equation in terms of dimensionless groups similar to that of Hixson and Baum, Sherwood and Gilliland, and Rushton and Oldshue. The close agreement between the theoretical and experimental values of the exponent of the Schmidt number in this equation may provide new and significant evidence for the applicability of the surface‐renewal theory to mass transfer from a flat solid surface into a turbulent liquid. For free rotational agitation, a local mass transfer coefficient with respect to the position of a cast solid was detected quantitatively. However, the insertion of four baffles into the tank gave a uniform mass transfer coefficient regardless of the position of the cast solid. A decrease in the mass transfer coefficient was observed when baffles were used. The advantages of the constant and stationary interface, the stability and simplicity of the apparatus, the possibility of duplicating experimental results, and the success of the detection of a local mass transfer coefficient suggest that the present apparatus and procedures could be used for the study of the theory of mass transfer rates from flat surfaces.