Fill the tube with nitrogen, remove the stopper and filter off the supernatant liquid by the method described previously using a clean filter paper on the filter stick.
When filtration is completed remove the filter assembly and turn off the nitrogen supply. Untie the filter paper and scrape back any product into the tube. Wash the product with two batches of the low boiling petroleum ether as described earlier. Stopper the tube and evacuate to dryness for about 10 min. Finally, fill the tube with nitrogen and shut down the apparatus.
NB: Remember to remove the liquid nitrogen dewar.