A new understanding of the relationship between solubility and particle size

Most discussions of the relationships between crystal solubility and particle size have hitherto been concerned with vapor condensation and have led to the prediction that the vapor pressure increases with curvature. Here, thermodynamic arguments are presented to show that such relationships, describing crystal solubility as a function of particle size, originally put forward by Ostwald and later corrected by Freundlich, may be unjustified for determining interfacial tension at solid-liquid interfaces. The Kelvin or Gibbs-Thomson equations are valid for liquid-vapor systems, but not for solid-liquid interfaces. Recent experimental observations have demonstrated that interfacial tension data obtained by the solubility-size approach are unreasonable. This leads to the conclusion that "Ostwald ripening" may not be due to a higher solubility of smaller crystals, but rather to a net negative interfacial tension between solid and solution.