Secrets of the purple smoke of first high explosive created by alchemists revealed

The mystery behind why the world’s first high explosive, fulminating gold, produces a purple smoke when it detonates has been solved, finally resolving a 400-year-old alchemical puzzle.

Fulminating gold is not actually a chemical fulminate, a compound containing the ion CNO^-, such as mercury(II) fulminate or silver fulminate. Instead, it is a mixture of a number of different compounds with gold(III) compounds complexed with ammonia providing most of the explosive punch. Its name comes from its explosive nature, from the Latin fulmen, or lightning. It was first mentioned by alchemists in the 16th century, and described by the German alchemist Sebald Schwaertzer, purportedly in 1585, to create ‘a beautiful, purple-coloured Aurum Fulminans’ within four days.