# Does the reaction of sulfur and potassium nitrate involve production of sulfur trioxide?

I've heard that oxidising sulfur with potassium nitrate yields $\ce{SO3}$ gas, but can't find a definitive answer anywhere.

Is sulfur trioxide produced? More generally, what's the full reaction?

• There is nothing definitive about it. Oxidizing S with KNO3 is a pretty violent reaction, and it may involve a lot of things. – Ivan Neretin Apr 19 '17 at 20:35

Generally a mixture of sulfur, potassium nitrate with charcoal or an organic carbon compound is used in gunpowder mixture.

$$\ce{3C + S + 2KNO3 → 3CO2 + N2 + K2S}$$

(Source)

There are many questions in chem.SE related to gunpowder and explosives which are all based on this reaction. You can find them of help.