Anhyd. Na2SO4 was crystd. from its aq. sal. in mixed reactors (0.2-5 L)under vacuum evapn. (430 hPa, 80 degrees C) at varying residence time (1135-4012 s), evapn. rate (0.980-35.433 g/min), suspension d. (22.13-129.63 kg/m(3)) and stirrer speed (450-1950 rpm) to study the process kinetics and to det. the linear crystal growth and effective nucleation rates. The correlations between kinetic parameters of the crystn. and supersatn., magma d. and mixing intensity were derived from the expt. data. The detd. order of crystal growth rate was about 1.4 for all crystallizers. The exponents in the equations describing the effect of the growth rate, magma d. and stirrer speed on the nucleation rate were 0.85, 1 and 2.5, resp. The scale-up principles to achieve the same median crystal size were developed. Over the range studied, a modest increase in median crystal size with increasing vol. of the crystallizer was obsd. for a const. sp. power input.