Sciencemadness Discussion Board

Sulphur candles

Swinfi2 - 29-2-2020 at 19:27

I'm experimenting with convenient ways to make SO2.

So far I've tried heating sulphur with sulphuric acid/bisulphate and it was fast but awful with subliming sulphur melting, passing through my glassware and the unfriendly to glass temperatures. I got about 1/10th absorption and needed a gas mask for a significant amount of time. Not so recomendable imo.

I've tried burning the element, the red pools and blue flame look cool, but tend to leave a layer of incombustable black tar and go out constantly. Probably a purity issue.

Has anyone got experience with or resource on sulphur candles? I'm trying to make them based info off a random website ("melt wax add sulphur til thick but pourable") is hardly precise instructions. Anyway the 3 I've made so far didn't burn so well but better than the raw sulphur.

Pic to follow of how/Why but I want the candles to fit through a 24/** joint.

Swinfi2 - 29-2-2020 at 19:40

20200301_033812.jpg - 4.9MB

j_sum1 - 29-2-2020 at 21:17

I have done it a couple of times. Following something nurdrage did in his early years.
I used a small tuna tin as a container. A little rolled up corrugated cardboard helps with wicking. Then topped up with elemental sulfur.
Over that is an inverted funnel attached to a tube then into my reaction. On the other side of the reaction I bubbled it through concentrated NaOH solution and a water scrubber before the suction pump. An aspirator would probably work well here.
I used some metal tubing since the gas comes off quite hot. I also made a small hole in the suction line to moderate the throughput.
Not too messy. Reasonably controllable. No escaping gas causing problems.

woelen - 1-3-2020 at 03:27

The easiest way to conveniently make SO2 is dripping moderately concentrated H2SO4 (e.g. 50%) on solid sodium metabisulfite or potassium metabisulfite. The sulfite or metabisulfite should be easy to obtain in nearly every country. If you don't have H2SO4, then you could try mixing the sulfite with NaHSO4 and dripping a little water on the mix and gently heating the mix.

The gas produced in this way contains some water vapor. If it must be dry, you can lead the gas through a tube, filled with anhydrous MgSO4 (which can be made from MgSO4.7H2O by heating that).

I have made SO2 in the above way several times for different experiments. Hassling with burning sulfur and getting a reliable flow from that I never tried. Too troublesome. You also get small amounts of SO3 when you burn sulfur and this may be very corrosive for certain equipment.

Harristotle - 1-3-2020 at 05:30

I have made sulfur candles for treating a hive after it had wax moth.
I melted sulfur (Gardening) then added bees wax. I used a wick I salvaged from an old candle, and a Berocca tin to mould the candle.
It was effective at making SO2, and after treatment I stored the 5 frame nuc in a bag until the next season. This was how the old skep German beekeepers used to do it. (Mind you, a strong hive will remove wax moth anyway, with more experience now I'd just feed them to build them up)

Cheers,
H.

Herr Haber - 2-3-2020 at 04:08

Sulphur wicks are used to sterilize wine barrels.
Available on Amazon :)

DavidJR - 4-3-2020 at 16:08

Quote: Originally posted by woelen  
The easiest way to conveniently make SO2 is dripping moderately concentrated H2SO4 (e.g. 50%) on solid sodium metabisulfite or potassium metabisulfite. The sulfite or metabisulfite should be easy to obtain in nearly every country. If you don't have H2SO4, then you could try mixing the sulfite with NaHSO4 and dripping a little water on the mix and gently heating the mix.

The gas produced in this way contains some water vapor. If it must be dry, you can lead the gas through a tube, filled with anhydrous MgSO4 (which can be made from MgSO4.7H2O by heating that).

I have made SO2 in the above way several times for different experiments. Hassling with burning sulfur and getting a reliable flow from that I never tried. Too troublesome. You also get small amounts of SO3 when you burn sulfur and this may be very corrosive for certain equipment.


I agree that (meta)bisulfite + acid is the easiest way. I usually add some water to the flask along with the solid though, but not enough to totally dissolve it.

For drying I would normally bubble it through concentrated sulfuric acid. I'm not sure whether or not that works better than magnesium sulfate in this case. The acid does seem to dissolve a moderate amount of SO2 though so maybe magnesium sulfate would be more efficient.

I've also tried using sodium sulfite rather than bisulfite, and although it works, it's much more of a hassle because of issues with insolubility.