# How can I clean solid sulfur and its oxides from test tube?

I was experimenting with sulfur few years ago. The test tube I used for that purpose has still sulfur stuck onto it. I was searching for a way to dissolve it.

I found an idea to try warm acetone. Sounded like cheap solution, but doesn't work - or it will take ages to dissolve.

I'm not a chemist, so I don't have any strange chemicals at home.

• 1. You don’t have sulfur oxide, because it’s a gas. 2. If your sulfur is in the form of sulfate salt, use water. Many sulfates are soluble in water. 3. Just dump the test tube. Easier, cheaper, and healthier. – Gimelist May 20 '18 at 10:57

There are a couple of ways to do it depending on what chemicals are available to you. Since sulfur melts around $115~\mathrm{^\circ C}$, you might first melt it and let as much liquid drip out of the test tube as possible in order to make the following step easier.

• Perhaps the most straightforward method involves toluene or xylene which you can probably purchase at a hardware store. Put some toluene or xylene in the test tube and heat it up (note: be careful, toluene and xylene are flammable), the sulfur should slowly dissolve. Pour the waste liquid out while hot. Repeat the process if necessary. If you can find both toluene and xylene, pick the xylene because it has a higher boiling point - it can get hotter and dissolve the sulfur better.
• Chromic acid (sulfuric acid and potassium dichromate) will remove sulfur. Pour the chromic acid into the test tube and let it sit for a couple of days, then pour it out, and with the help of a spatula, you should be able to remove the sulfur as a solid chunk.
• Carbon disulfide dissolves sulfur, but $\ce{CS_2}$ is toxic and extremely flammable
• The chrome VI species in cromic acid are highly toxic/cancerogenic. Don't. – Karl Apr 17 '16 at 10:58
• It would no doubt be cheaper to buy a new test tube than the chemicals needed to dissolve the sulfur. SAFETY I wouldn't heat toluene, xylene or carbon disulfide over a open flame. // Chromic acid is a common cleaning solution in a chem lab, but it is really nasty since it oxidizes "most" things. Not really something for a typical home lab in my mind. – MaxW Jan 17 '17 at 22:27

Since you stated:

I'm not a chemist, so I don't have any strange chemicals at home.

you will neither have facilities for their proper storage and waste management.

Consequently, the only reasonable solution is: Get some new test tubes (about 0.20 Euro for a 160 x 16 mm tube), but don't risk your own health or pollute the environment by messing around with carcenogenic ($\ce{CrO3}$ in $\ce{H2SO4}$) or neurotoxic ($\ce{CS2}$) agents.

• If you were a chemist, and had the facilities and chemicals: Still dump that test tube. – Karl Apr 12 '16 at 20:15

I once had this problem in the lab. I put some NaOH (I guess it can be found in some bleaches or cleaning supplies for declogging pipes) and water in it. It warms in the process, but it's not a problem. After an hour or so, and after bit of scratching (watch out, the brush might decompose in such basic solution), the sulfur was gone.

• About the sodium hydroxide (NaOH) option: I've had sulfur residue attached to my condenser. Letting the glassware 'bathe' in high concentration NaOH, then washing it of with 10% hydrochloric acid (HCl) only partly removed the sulfur. It was unfortunately still detectable, by smell, when doing a simple water distillation. – user28849 Apr 12 '16 at 17:59
• And I am not entirely sure the glass is immune from bathing in such concentrated sodium hydroxide, either. – Oscar Lanzi May 20 '18 at 10:09