A comparison of the kinetic and diffusional models for solid-liquid reactions occuring in a spherical particle is presented. The similarities and differences of the unreacted-core shrinking model and the homogeneous model are examined in light of the rate-controlling factors. In view of the similarity of the two models, it is shown that erroneous conclusions in regard to the mechanism and the activation energies may be drawn from an analysis of the experimental data. A more versatile model is developed in order to augment the two models so that wider varieties of solid-liquid reaction systems may be treated. The concept of effectiveness factors in solid-liquid reactions is introduced and the influence of diffusion is ascertained. The present study presents a better phenomenological understanding of the mechanism of mass transfer and chemical reaction occuring in water pollution between liquid and solid. (Author)