Several organic liquid-phase reactions are carried out in the presence of a sparingly soluble reactive solid phase which is gradually dissolved during the course of the reaction. The presence of the reactive solid phase complicates the treatment of kinetic data, since the overall reaction rate is influenced by the solubility equilibrium and mass transfer rate of the solid compound. A mathematical model has been derived for an organic reaction system with one reactive solid compound. The modelling concept was applied on a linear multistep reaction system, Claisen condensation. The solubility of the solid compound was measured under non-reactive conditions and the kinetic parameters for the reaction system were determined from the data obtained with semibatch experiments. Model simulations elucidated the behaviour of the sparingly soluble reactive compound in the process and they indicated that the rate equations describe the experimental kinetic data well.