Growth and dissolution of NaClO₃ crystal in aqueous solution

Abstract

Growth and dissolution rates of {100} faces of NaClO₃ crystals of about 0.5 mm across have been measured, along with in-situ observations of both processes, under a wide range of well-controlled super- and under-saturations, 1.1∼49%, and 1.6∼4.5%, respectively. The experiments were made using a specially designed apparatus, with which both growth and dissolution experiments can be made on the same seed crystal. The growth mechanisms are analysed based on the relation between the bulk supersaturation σ_B and the growth rate R. Physical constants, such as γ′⁄kT, etc. were evaluated.
It is concluded that in the lower supersaturation range than σ_B≈2.5% BCF mechanism predominates, in moderate supersaturation range 2.5<σ_B<8.0%, Birth and Spread mechanism of two dimensional nucleation growth is the major growth mechanism, and in much higher supersaturation range, 8.0%>σ_B, maximum linear law is assumed to be operated. Dissolution mechanism is also briefly discussed, in which the importance of interface kinetics is stressed. The observations on the recovery process from rounded to facetted morphologies and on the occlusion of liquid inclusions are described as well.