Overview. Europe did not learn of gunpowder until the late twelfth century. By that time, the Chinese had perfected the "barrel gun" and the cannon. However, it was not invented by people looking for better weapons or even explosives, but by alchemists in search of the elixir of immortality.

Saltpeter. Gunpowder has three main ingredients: saltpeter or potassium nitrate, sulfur, and charcoal. Long before saltpeter could be used as a component of explosives, it was used for its capability to turn ores into liquid and to dissolve other indissoluble minerals, such as cinnabar, into water solutions. Saltpeter was used for this purpose at least by the second century B.C.E., as well as for a flux to help metallurgical processes. The potassium flame test is crucial for detecting saltpeter, which burns with a violet or purple flame. This test for true saltpeter...