Meanwhile, take a clean polythene tube with attached stoppers and fix a filter paper over one end. Insert the other end into a clean Schlenk tube E and purge the system with nitrogen for a few minutes via the side-arm tap: this procedure is shown in Figure 4. When the solid has dissolved connect a nitrogen supply to the side-arm of tube D and remove the stopper carefully.

Insert the filter stick into tube D, insert an outlet needle into tube E, and close the side-arm tap on E. Lift tube D from the bath and transfer the dissolved product from D to E by lowering the filter stick into the solution (Figure 4).

When transfer is complete connect a nitrogen supply to tube E and remove the stopper and filter assembly. Re-stopper and stand the tube in an ice bath for about 20 min. to crystallise the product.