Aq. soins. of 2Na(2)SO(4)/2Na(2)SO(3)/H2O (wt. ratio of about 1:1) and 2Na(2)SO(4)/2Na(2)SO(3)/NaHSO3 (Na2S2O5/H2O (Na2SO4 7,38-8,45%, 2Na(2)SO(3) 6,32-7,39%, NaHSO3 19,43-20.90%) were studied for crystn. at about 82 degrees C and 430 kPa in a 0.2 dm(3) continuously operated evaporative crystallizer for 6 residence times at varying residence time (1281-5197 s), intensity of evapn. (0,60-1,95 g/min), suspension d. (12.45-151,6 kg/m(3)) and a constant stirrer speed (950 rpm) to det. the linear crystal growth and effective nucleation rates of the double 2Na(2)SO(3) center dot 3Na(2)SO(4) sat crystals from population d plot by using the mixed-suspension-mixed-product-removal crystallizer model. The detd. order of crystal growth rate was about 2 (for supersatn. expressed in terms of activities), relative kinetic order was below 1 and exponent of the suspension d. was about 0.2 in both systems. The correlations between kinetic parameters of crystn., residence time and magma d., valid for both systems were derived from expti. data.