We prepared a suspension of calcium oxalate monohydrate
seed crystals by adding 100 mg of the crystals (Merck, A.G.)
to 100 mL of distilled and Millipore-filtered water. A homogeneous suspension was obtained by ultrasonication. The
crystal suspension was carefully mixed at 37 #{176}C and stored at
this temperature for at least 24 h before being added to the
crystallization system.