Cracking powder
The Glaubersche bang powder is a mixture of potassium nitrate , potassium and sulfur . When heated slowly, it first melts and then detonates after a while with a loud bang - in contrast to black powder , which deflagrates (i.e. it "explodes" at less than the internal speed of sound). If the powder is ignited without melting beforehand, it will burn off without an explosion, albeit violently. This mixture was first mentioned in 1648 by the alchemist Johann Rudolph Glauber in his book Philosophical Ovens .