Spirit of Salt: Hydrochloric Acid from Sea Salt and Oil of Vitriol

Hydrochloric acid, once called spirit of salt or muriatic acid, is hydrogen chloride gas dissolved in water. Strong sulfuric acid poured on common salt drives the gas off; water takes it up greedily. Andrew Ure described the British way in 1839: salt and oil of vitriol in cast-iron pots, the gas led through a tube into large glass globes part-filled with water. The commercial acid had a specific gravity of 1.15 to 1.20, a little under 40 % acid.