The English philosopher and alchemist Roger Bacon is thought by modern historians to be the first European to have come across gunpowder. In 1248 a missionary brought him a Chinese device known as a "firecracker" that was used in celebrations. Intrigued, Bacon took it apart and analyzed the contents to discover why it exploded rather than merely burned. He soon worked out that the black substance, which was to become known as gunpowder, was a mixture of saltpetre and other chemicals. Bacon also apparently realised the huge danger that this innocuous-looking powder presented, and in his report he enciphered the formula - an attempt to keep it a secret for as long as possible. To find the true origins of gunpowder, however, we must travel a few hundred years backward in time, and a few thousand miles to the East.

Although the early history of gunpowder is murky, it is believed to have been invented in China at about 900AD. Taoist alchemists had been searching for the elixir of immortality, and were testing compounds such as saltpetre. Around this time it was discovered that the addition of two common substances - charcoal and sulphur - improves the rapid burning of saltpetre into an explosion. Sulphur is long known to science, and by 200AD was being produced by roasting iron sulphide.

The scientific principle behind explosives is simple enough. A mixture of solids must burn vigorously to produce a large volume of gas, which rapidly expands from the heat of the reaction. The saltpetre is an oxidant, and allows the charcoal to burn far quicker than if it only had access to oxygen in the air.

2KNO3(s) + 3C(s) + S(s) -----> N2(g) + 3CO2(g) + K2S(s)

The Chinese used this reaction for noisemakers and signalling rockets at first. The earliest mention of gunpowder being employed for warfare dates to 1046. The first recognisable cannon or firearm with an enclosed blast chamber didn't arise until 1288.

Despite Bacon's best efforts, Europeans discovered the formula and applied it to killing each other with great zeal. Weapon designs developed rapidly, and gunpowder formulas were perfected. In 1429, two Czech alchemists devised granulated gunpowder, which is much more powerful and consistent, and less vulnerable to moisture. Gunpowder revolutionised warfare during the 16th century, as ancient fortresses were suddenly vulnerable to cannons, and guns became small enough to be wielded effectively by infantry. It is acutely ironic that one of the most destructive inventions in history was originally developed from research into achieving immortality.

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