 It was historically called acidum salis and spirits of salt because it was produced from rock salt and "green vitriol" (Iron(II) sulfate) (by Basilius Valentinus in the 15th century) and later from the chemically similar common salt and sulfuric acid (by Johann Rudolph Glauber in the 17th century).Free hydrochloric acid was first formally described in the 16th century by Libavius.Later, it was used by chemists such as Glauber, Priestley, and Davy in their scientific research.