Hydrochloric Acid
(HCl), a gaseous compound of equal volumes of hydrogen and chlorine. It is evolved during volcanic eruptions, and is found in the water which collects in the crevices of mountains, as well as in rivers which take their rise in volcanic formations, especially in South America. It may be produced by decomposing common salt with sulphuric acid (2Na Cl+ H2SO4 =2HCl + Na2SO4), or by bringing equal volumes of chlorine and hydrogen together and exposing the mixture to diffused daylight with condensation, as it explodes in direct sunlight.