Inadvertent discoveries make for the most entertaining ones. And the most indignant scientists’ wives.
Hamburg, Germany, 1669: Alchemist Hennig Brandt boils fetid urine until the leftovers (in an air-exposure-preventing container) explode. Thus discovering elemental phosphorus.
Guy made himself a primitive light bulb to study by out of the stuff.
Nancy, France, 1832: Legitimate chemist Henri Braconnot messes around in his workspace with nitric acid, wearing only the wife’s cotton apron for protection. Said apron becomes splattered with said acid and, when hung up by the fire to dry, suddenly disappears in a flash of expanding gases.
Thus was discovered nitrocellulose (cellulose nitrate), or guncotton. A major technological advance and military advantage over gunpowder.