Black Powder Composition

Chemical Composition of Black Powder or Gunpowder

This woman is making firecrackers using gunpowder. It's risky to handle gunpowder, so don't mess with it unless you know what you're doing!
This woman is making firecrackers using gunpowder. It's risky to handle gunpowder, so don't mess with it unless you know what you're doing!. De Agostini / C. Sappa, Getty Images

Black powder is the name given to the earliest known chemical explosive. It is used as a blasting powder and a propellant for firearms, rockets, and fireworks. The composition of black powder or gunpowder is not set. In fact, several different compositions have been used throughout history. Here's a look at some of the most notable or common compositions, plus the composition of modern black powder.

Black Powder Basics

There's nothing complicated about the formulation of black powder. It consists of charcoal (carbon), saltpeter (potassium nitrate or sometimes sodium nitrate), and sulfur. Charcoal and sulfur act as the fuel for the explosion, while saltpeter acts as an oxidizer. Sulfur also lowers the ignition temperature, which increases the combustion rate.

Charcoal is used instead of pure carbon because it contains incompletely decomposed cellulose. It has a much lower autoignition temperature. Black powder made using pure carbon will ignite, but it won't explode.

In commercial black powder preparation, potassium nitrate or another nitrate (e.g., sodium nitrate) usually is coated with graphite (a form of carbon). This helps prevent electrostatic charge build-up, reducing the chance a stray spark will prematurely ignite the mixture.

Sometimes black powder is tumbled with graphite dust after it is mixed to coat the grains.

In addition to reducing static, the graphite reduces moisture absorption, which could prevent gunpowder from igniting.

Notable Black Powder Compositions

Typical modern gunpowder consists of saltpeter, charcoal, and sulfur in a 6:1:1 or 6:1.2:0.8 ratio. Historically significant formulations have been calculated on a percentage basis:

 

FormulaSaltpeterCharcoalSulfur
Bishop Watson, 178175.015.010.0
British Government, 163575.012.512.5
Bruxelles studies, 156075.015.629.38
Whitehorne, 156050.033.316.6
Arderne lab, 135066.622.211.1
Roger Bacon, c. 125237.5031.2531.25
Marcus Graecus, 8th century69.2223.077.69
Marcus Graecus, 8th century66.6622.2211.11

 

Source: The Chemistry of Gun Powder and Explosives