In need of a combustion reaction which produces sulfur

[Durandal]

Just like the title says. I'm writing a fic, and there's a part where a chemical reaction has resulted in a burnt circle of dirt on the ground that smells of sulfur. Is this a possible outcome of a combustion reaction? For storytelling purposes, I'd like a reaction product that has a distinct smell.

[Dooey Jo]

Do you want the smell of actual sulphur, which doesn't smell very much at all (it smells a bit like matches), or the smell that is commonly associated with burning sulphur, ie. sulphur dioxide?

Because it's very easy to get sulphur dioxide, and many combustion processes containing sulphur will yield it. Burning black powder (especially of lesser quality) can produce a quite sulphuric smell, for example. I don't know of any reaction that will produce elemental sulphur, though.

[Gil Hamilton]

Sounds like you are trying to avoid saying the phrase "smells of brimstone" there.

As Dooey Jo says, it's often the biproducts that give the smell of sulfur, since not too many reactions spit out elemental sulfur (most of those, I recall, are reasonably non-spontaneous).

If you want a cool reaction that will definitely leave a good burn mark and will smell like brimstone, consider zinc and sulfur.

8 Zn (s) + S8 (s) --> 8 ZnS (s)

In fact, the stuff pretty much combusts explosively if you mix it in the right proportions. However, it needs to be heated to a fairly high temperature to do anything (usually heating the tip of a metal wire or rod till it's glowing cherry and then very carefully poking the mixture will set it off).

Doing the same reaction with iron has similar effects, but it doesn't blow up. That, however, makes an awesome red flame.

[Kuroneko]

If you want a cool reaction that will definitely leave a good burn mark and will smell like brimstone, consider zinc and sulfur.
8 Zn (s) + S8 (s) --> 8 ZnS (s)

Speaking of zinc, since zinc ore is typically some form of sphalerite, how feasible is 2ZnS + 3O₂ → 2ZnO + 2SO₂ from a sphalerite? Zinc ore may be advantageous for some stories since it would be more common than elemental zinc, although it would more difficult to burn quickly. I suspect it may do reasonably well in powdered form, but I'm far from certain about that.

[Gil Hamilton]

Speaking of zinc, since zinc ore is typically some form of sphalerite, how feasible is 2ZnS + 3O₂ → 2ZnO + 2SO₂ from a sphalerite? Zinc ore may be advantageous for some stories since it would be more common than elemental zinc, although it would more difficult to burn quickly. I suspect it may do reasonably well in powdered form, but I'm far from certain about that.

I chose zinc and sulfur because the reaction would certainly learn a burn mark and smell like brimstone. And it's something I've actually reacted, so it came to mind.

However, zinc sphalerite will burn in oxygen readily, but you would have to powder it pretty good first, since I don't think a chunk of the crystal could be ignited. To be fair, you have to do that to make elemental zinc burn easily you have to make it pretty finely grained too. Plus, sphalerite has the advantage that in some historic settings being valuable and it evolves SO2 gas, making it potently sulfurous in smell.