All experiments are carried out in a fluidized bed
crystallizer. More details about set up and
procedure are to be found in Refs. [1,2]. Saturated
solutions of Epsomite at 25 C are prepared
according to the solubility data of Mullin [3].
Changing the pH-value of the solution is done by
addition of H2SO4 to obtain acidic solutions and
NaOH to obtain higher alkaline solutions. In case
of growth rate measurements in dependence of
impurity concentrations a carefully weighed
amount of each impurity is added to the solution.
Seed crystals were obtained from sieve fractions
with a mean size of 1 mm. In all runs the initial
weight of seed crystals was 3 g. After 15 min the
crystals were washed, dried at room temperature
and weighed. The difference in weight of the
crystals before and after the experiment is used in
calculating the growth rate or the dissolution rate,
respectively.