 Unless pressurized or cooled, hydrochloric acid will turn into a gas if there is around 60% or less of water.Hydrochloric acid is also known as hydronium chloride, in contrast to its anhydrous parent known as "hydrogen" chloride, or dry HCl.Hydrochloric acid was known to European alchemists as "spirits of salt" or "acidum salis" (salt acid).