Potentiometric Determination of the Critical Supersaturation Ratio of Monodisperse Silver Chloride Grains in the Controlled Double-Jet Precipitation

Abstract

Critical supersaturation ratio, S^*, of monodisperse AgCl grains in the controlled double-jet precipitation was experimentally determined on the basis of a potentiometric measurement of supersaturation ratio, S, and theoretical relationships between S and the supply rate of reactants, Q. For cubic grains, the relationship is derived as (S-1) =Q/12DC_on_sL_s in S<S^* whereas (S-1) =Q/12DC_o (n_sL_s+n_nL_n) in S>S^*, where D the diffusivity, C_o the solubility of bulk solid, n_s and n_n the numbers of seed grains and new nuclei, respectively, and L_s and L_n the edge lengths of seed grains and new nuclei, respectively. The critical supersaturation ratio was defined as S at the inflection point in the relationship between (S-1) and Q/n_sL_s. The definition of S^* was confirmed with transmission electron microscopy. Under the condition of pCl 3.0 and 50°C, S^* was determined as 1.077-1.097 and almost independent of the size and number of seed grains. The critical nucleus size, critical growth rate, and magnitude of driving force of growth were also discussed.