Gunpowder (a.k.a black powder) is a mixture of sulphur, charcoal, and potassium nitrate. Gunpowder is a compound that can be made just using potassium nitrate and charcoal, but without the sulphur, the powder is not as strong as with the sulphur. It burns rapidly, producing a volume of hot gas that is made up of carbon dioxide, water, and nitrogen, and a solid residue of potassium sulfide. Because of its burning rate and properties and the amount of heat and gas volume that it can generate, gunpowder has and is been widely used as a propellant in firearms and as a pyrotechnic composition in fireworks. The term of gunpowder also refers broadly to any powder that has propellant. Though modern firearms do not use the traditional gunpowder, instead they use smokeless powder. The burn rate of gunpowder can be changed by corning. Corning first compresses the fine black powder formula into blocks with a fixed density of around 1.7 g/cm³. The blocks are then broken up into granules. These granules are then sorted by size to give various grades of black powder. Different grades of black powder are use for different things. In the U.S., standard grades of black powder runs from the coarse Fg grade that are used in large bore rifles and small cannons. Through FFg which is used in medium and small-bore weapons such as muskets and fusils, FFFg used in small-bore rifles and pistols, and FFFFg that is used in extreme small bore, short pistols and for priming flintlocks. A simple, in a way, chemical equation for the combustion of black powder is 2 KNO3 + S + 3 C → K2S + N2 + 3 CO2.
The more accurate, though simplified a bit, is
10 KNO3 + 3 S + 8 C → 2 K2CO3 + 3 K2SO4 + 6 CO2 + 5 N2.
Burning gunpowder does not take place as a single reaction, and the byproducts are not easily predicted. One study's results showed that it produced: 55.91% solid products: potassium carbonate, potassium sulfate, potassium sulfide, sulfur, potassium nitrate, potassium thiocyanate, carbon,...