Magnesium sulfate (or magnesium sulphate) is an inorganic salt (chemical compound) containing magnesium, sulfur and oxygen, with the formula MgSO4. It is often encountered as the heptahydrate sulfate mineral epsomite (MgSO4_7H2O), commonly called Epsom salt, named for a bitter saline spring from the town of Epsom in Surrey, England, where the salt was produced from the springs that arise where the porous chalk of the North Downs meets non-porous London clay. Epsom salt occurs naturally as a pure mineral. Another hydrate form is kieserite. Anhydrous magnesium sulfate is used as a drying agent. Since the anhydrous form is hygroscopic (readily absorbs water from the air) and is therefore difficult to weigh accurately, the hydrate is often preferred when preparing solutions, for example in medical preparations. Epsom salt has been traditionally used as a component of bath salts. Magnesium sulfate is highly soluble in water. The anhydrous form is strongly hygroscopic, and can be used as a desiccant. Epsom salts have medicinal properties when used both externally and internally. Magnesium sulfate is the primary substance that causes the absorption of sound in seawater (acoustic energy is
Contributions by Rifleman 82, Jfdwolff, and Edgar181.