The Thermal Effects of Nucleation and Crystallization of KBr and KCl Solutions. II. The Heat Of Nucleation and the Supersaturated Solution

Abstract It is shown that the induction period commonly observed in the crystallization of salts from aqueous solutions is due to a heterogeneous nucleation process made apparent by the release of heat. The metastable supersaturated solution is therefore a solution of particles, and the supersaturation limit can be extended by the addition of a good nucleator. In the case of KBr and KCl the halogenoplumbate complex ions are good nucleators. The heat evolved during the nucleation process is proportional to the concentration of the lead ions and the supersaturation limit is a kinetic function of the concentration of the lead ions. The size of the fine particles that can be held in a supersaturated solution and σ, “the crystal‐liquid surface tension”, were determined by the use of the Ostwald‐Freundlich equation. The thermal effects can thus be quantitatively accounted for.