Particle breakage commonly occurs in stirred vessels such as crystallizers. Since particle breakage can have significant cost implications, efforts have been taken to quantify the amount of breakage in stirred vessels. Experimentalists usually perform breakage experiments in a saturated solution or in a non-solvent to prevent other mechanisms such as growth and nucleation. The reason for this is that it is very difficult to determine whether a small particle is a fragment from breakage or whether it was produced by nucleation. One concern with the experiments in saturated solutions is that the effect of Ostwald ripening is not known. Ostwald ripening is the phenomenon where large particles grow larger at the expense of smaller particles dissolving in the saturated solution. For this reason, many particle breakage experiments in the past have been performed in a non-solvent. However, those experiments cannot be considered exactly representative of real world situations where particles grow and break in saturated solutions. Consequently, questions have been raised on the validity of particle breakage experiments that attempt to quantify the amount of breakage in stirred vessels. Although Ostwald ripening is expected to come into play at particle sizes smaller than 1 micron, suggestions have been made that it might still be affecting the particle breakage experiment results even though many of the particles are larger than 300 microns. That is, if a significant quantity of small particles is formed, they could dissolve and significantly change the shape of the larger particles.

This paper addresses the effect of Ostwald ripening in particle breakage experiments using a novel method. Since it is impossible to follow one single particle in a stirred vessel, the particle is studied using a microscope hot-cold stage to control the temperature, and a microscope to determine changes in particle size and shape. Experiments are performed with both saturated solutions and non-solvents. If there is no difference between the results with the saturated solutions and the non-solvents, then ripening is not having a significant effect. Since Ostwald ripening is expected to have a stronger effect on particles with sharp edges, some tests are performed with broken particles. Various systems (water-potash alum, water-sodium chloride etc.) are studied with different particle sizes and the results are presented.