In 1646, Glauber made potassium silicate, that he termed "liquor silicum" by melting potassium carbonate (obtained by calcinating cream of tartar) and sand in a crucible, and keeping it molten until it ceased to bubble (due to the release of carbon dioxide). The mixture was allowed to cool and then was ground to a fine powder. When the powder was exposed to moist air, it gradually formed a viscous liquid, which Glauber called ""Oleum oder Liquor Silicum, Arenæ, vel Crystallorum"" (i.e., oil or solution of silica, sand or quartz crystal).