MECHANISM OF THE PREPARATION OF INSOLUBLE COMPOUNDS BY LOCAL GROWTH IN AQUEOUS-SOLUTION

Stable and controlled-size particles of very insoluble products can be prepared by a method of local growth. The growth takes place at the interface between a solid reactant and a solution containing the other reacting compound. The mechanism of this process is studied taking hexacyanoferrates as examples. The influence of parameters such as the nature of the starting materials, concentration and temperature is studied by potentiometric and radiochemical methods, and by optical microscopy. The results are interpreted by a mechanism based on osmosis. From this mechanism, experimental conditions for the preparation of insoluble compounds by local growth can be predicted, using water activities calculations.