On the measurement of crystal size distributions in the micrometer size range

Abstract

The steady state crystal size distribution in a continuous mixed suspension mixed product removal crystallizer has been measured during the precipitati of calcium oxalate trihydrate from aqueous solution. Two different instruments, both working over the size range 1.4–25 μm, were used, a Coulter Counter and an instrument based on the principle of forward scattering of laser light. The form of size distribution obtained with both instruments was very similar and lends confidence to such measurements at these sizes. The crystal number density for sizes less than about 5 μm was much higher than expected from the number density at larger sizes. This behaviour is similar to that found for systems of higher solubility but raises important questions concerning the reasons for such effects.