FORMATION AND GROWTH OF NUCLEI BY SECONDARY NUCLEATION IN AGITATED SOLUTION OF K-ALUM

From the changes in light transmittance and electrical conductivity of a solution with elapsed time and from the size distribution of the final product crystals, the kinetics of the cited processes was studied. The experimental conditions are as follows: initial solute concentration, C0 [g-mol/l] =0.22-0.38; relative supersaturation ratio (C/Cs)-1=5-1=0.01-0.33; temperature 20-35°C; agitation rate 630, 1100rpm; seed crystal, 1-10 in number, size 325μ. Over the ranges of S-1=0.04-0.3, the rates of growth and nucleation were given by the following equations: dr/dt=G=kg(S-1)ng, (ng=1-1.4) and dN/dt=knNm2(S-1)nn=kn''Nm2G(S-1)nn'', (nn=1.7-2.0, Hnf=0.6-0.7). Nm is the number of crystals with radius larger than rmin, which is the radius of the smallest among the crystals breeding the secondary nuclei and which was estimated to be 100-120μ. It is suggested that nucleation takes place due to collision among the crystals, and that the probability of the formed nuclei remaining able to grow depends on (S-1).