Measurements of the liquid-solid mass transfer coefficient k(S) were performed in a three-phase multiple impeller and stationary catalytic basket reactor, called a Robinson-Mahoney reactor. Local coefficients were determined using naphtol particle dissolution in water and n-heptane with or without gas flow. Experiments have shown that local coefficients k(S) (loc) depend on the particle position in the basket, agitation speed, and liquid properties. A correlation linking k(S) to liquid velocity was established in a reactor simulating hydrodynamics in a piece of catalytic basket. Liquid velocity values were validated using a particle image velocimetry technique in a Robinson-Mahoney reactor, using water. (c) 2005 American Institute of Chemical Engineers.