Simulation was performed for crystallization of potassium sulfate from an unseeded aqueous solution whose temperature was lowered at a constant rate. The metastable zone width (MSZW) was defined as the supercooling at which the number density of generated crystals reached a fixed value of (N/M)det. Secondary nucleation caused by grown primary nuclei had a significant effect on the simulated MSZW for the unseeded solution. It lowered the simulated MSZW at lower cooling rates with a low detection sensitivity (i.e. high value of (N/M)det). The secondary nucleation effect became weak at higher cooling rates with a high detection sensitivity and the MSZW was governed with primary nucleation only. In actual experiments of MSZW, therefore, higher cooling rate with a high detection sensitivity is preferable to deduce the kinetics of primary nucleation from MSZW data.
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