Q. How should the soxhlet apparatus be cleaned?

Answer

Overnight place the glass in a sealed container and submerge it in chromic acid that has been dissolved in concentrated sulfuric acid. After that a good amount of water should be used to rinse the glass. In later years it was discovered that chromium ions are extremely harmful to the environment and that chromic acid solution is a powerful human carcinogen. Both of these findings came about quite some time after the first discovery. A solution of hydrogen peroxide which can also be produced from sulfuric acid was discovered to be a suitable replacement for it. Be very careful not to use perchloric or hydrofluoric acid since either of these acids has the potential to or already has the ability to destroy the coarse disc on the glass thimble.