gunpowder, explosive mixture; its most common formula, called "black powder," is a combination of saltpeter, sulfur, and carbon in the form of charcoal. Historically, the relative amounts of the components have varied. An increase in the percentage of saltpeter (potassium nitrate) increases the speed of combustion. In the past gunpowder was widely used for blasting and for propelling bullets from guns but it has been largely replaced by more powerful explosives. Another form of powder containing potassium chlorate instead of the nitrate is commonly used in fireworks and in matches. The origin of gunpowder was probably Chinese, for it seems to have been known in China at least as early as the 9th cent. and was there used for making firecrackers. There is evidence suggesting that it came to Europe through the Arabs. Roger Bacon was long credited with inventing it because a formula for making it is given in a work attributed to him, and some German scholars have credited its invention to the alchemist-monk Berthold Schwarz. However, it is now generally agreed that gunpowder was introduced and not invented in Europe in the 14th cent. Its use revolutionized warfare and ultimately played a large part in the alteration of European patterns of living up until modern times. Gunpowder was the only explosive in wide use until the middle of the 19th cent., when it was superseded by nitroglycerine-based explosives.

Gunpowder Plot, conspiracy to blow up the English Parliament and King James I on Nov. 5, 1605, the day set for the king to open Parliament. It was intended to be the beginning of a great uprising of English Catholics, who were distressed by the increased severity of penal laws against the practice of their religion. The conspirators, who began plotting early in 1604, expanded their number to a point where secrecy was impossible. They included Robert Catesby, John Wright, and Thomas Winter, the originators, Christopher Wright, Robert Winter, Robert Keyes, Guy Fawkes, a soldier who had been serving in Flanders, Thomas Percy, John Grant, Sir Everard Digby, Francis Tresham, Ambrose Rookwood, and Thomas Bates. Percy hired a cellar under the House of Lords, in which 36 barrels of gunpowder, overlaid with iron bars and firewood, were secretly stored. The conspiracy was brought to light through a mysterious letter received by Lord Monteagle, a brother-in-law of Tresham, on Oct. 26, urging him not to attend Parliament on the opening day. The 1st earl of Salisbury and others, to whom the plot was made known, took steps leading to the discovery of the materials and the arrest of Fawkes as he entered the cellar. Other conspirators, overtaken in flight or seized afterward, were killed outright, imprisoned, or executed. Among those executed was Henry Garnett, the superior of the English Jesuits, who had known of the conspiracy. While the plot was the work of a small number of men, it provoked hostility against all English Catholics and led to an increase in the harshness of laws against them. Guy Fawkes Day, Nov. 5, is still celebrated in England with fireworks and bonfires, on which effigies of the conspirator are burned.

Any of several mixtures used as propelling charges in guns and as blasting agents in mining. The first such explosive was black powder, a mixture of saltpeter (potassium nitrate), sulfur, and charcoal. It originated in the 9th century in China and made its way west in the 13th century. The recipe was refined and finally fixed in the 14th century; black powder is still widely used for ignition charges, primers, fuses, blank charges in military ammunition, and fireworks. In 1838 it was discovered that cotton could be made explosive by dipping it in concentrated nitric acid, and the form of nitrocellulose known as guncotton came into use as an ingredient of gunpowder in the 1860s. In the 1880s Paul Vieille (1854–1934) used nitrocellulose to create the first smokeless gunpowder; modern gunpowder consists of either nitrocellulose alone or a combination of nitrocellulose and nitroglycerin.

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(1605) Conspiracy by English Roman Catholic zealots to blow up Parliament and kill James I. Angered by James's refusal to grant more religious toleration to Catholics, a group of conspirators led by Robert Catesby (1573–1605) recruited Guy Fawkes to their plot. One member warned his brother-in-law Lord Monteagle not to attend Parliament on the appointed day (November 5, 1605), and Monteagle alerted the government. Fawkes was arrested in a rented cellar under the palace at Westminster, where he had concealed 20 barrels of gunpowder. Under torture, he revealed the names of the conspirators, and they were all either killed while resisting arrest or executed in 1606. The plot bitterly intensified Protestant suspicions of Catholics.

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