A process for carrying out a liquid/solid reaction comprises a) preparing a reaction suspension in which a first reactant is present in suspended form and a second reactant is present in dissolved form in a suspension medium, where one of the reaction products is insoluble in the suspension medium, b) passing the reaction suspension through an elongated reaction zone so that the Reynolds number of the stream is less than 20,000 and c) separating off the insoluble reaction product formed. The process has the advantage that the insoluble reaction product is obtained in a readily filterable form.