[Prince Phoenix]

Cleaning test tubes used for preparing different allotropes of Sulfur is difficult.I wasn't able to find any ways on the internet(May be because of bad internet skills?).
But our laboratory teacher made a mixture of Sulfuric acid and Potassium Dichromate K₂Cr₂O₇ . He poured it into the test tube which had Sulfur sticking to it. When we came back two days later, he told me to remove the sulfur after discarding the mixture. I pushed it with a tong and the sulfur came out as one big chunk without a single piece staying back. The test tube was clean. Can anyone explain what caused the sulfur to be removed? And are there any other ways of cleaning test tubes with sulfur sticking to them other than this?

[Fleaker]

Hot toluene/xylene is an acceptable solvent for sulfur. Carbon disulfide works much better, but it is also extremely flammable. Sulfur chlorides also work well.

The chromic acid solution you mentioned oxidized some of the sulfur sulfate or perhaps sulfur dioxide and helped facilitate removal.

The last option is heating your test tubes til the sulfur melts and drips out (~125C), and then heating them with excess air to burn out the film of sulfur left in the tube.

[mnakhla]

glacial acetic acid is a fairly good solvent for sulfur even at room temperature, it works wonders really