Magnesium sulfate is a chemical compound

Chemical compound

A chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms that are held together...

 containing magnesium

Magnesium

Magnesium is a chemical element with the symbol Mg, atomic number 12, and common oxidation number +2. It is an alkaline earth metal and the eighth most abundant element in the Earth's crust and ninth in the known universe as a whole...

, sulfur

Sulfur

Sulfur or sulphur is the chemical element with atomic number 16. In the periodic table it is represented by the symbol S. It is an abundant, multivalent non-metal. Under normal conditions, sulfur atoms form cyclic octatomic molecules with chemical formula S8. Elemental sulfur is a bright yellow...

 and oxygen

Oxygen

Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...

, with the formula MgSO₄. It is often encountered as the heptahydrate epsomite

Epsomite

Epsomite is a hydrous magnesium sulfate mineral with formula MgSO4·7H2O or simply MgSO4. Epsomite forms as encrustations or efflorescences on limestone cavern walls and mine timbers and walls, as a volcanic fumaroles, and as rare beds in evaporate layers...

 (MgSO₄·7H₂O), commonly called Epsom salt, from the town of Epsom

Epsom

Epsom is a town in the borough of Epsom and Ewell in Surrey, England. Small parts of Epsom are in the Borough of Reigate and Banstead. The town is located south-south-west of Charing Cross, within the Greater London Urban Area. The town lies on the chalk downland of Epsom Downs.-History:Epsom lies...

 in Surrey

Surrey

Surrey is a county in the South East of England and is one of the Home Counties. The county borders Greater London, Kent, East Sussex, West Sussex, Hampshire and Berkshire. The historic county town is Guildford. Surrey County Council sits at Kingston upon Thames, although this has been part of...

, England, where the salt was distilled from the springs that arise where the porous chalk of the North Downs

North Downs

The North Downs are a ridge of chalk hills in south east England that stretch from Farnham in Surrey to the White Cliffs of Dover in Kent. The North Downs lie within two Areas of Outstanding Natural Beauty , the Surrey Hills and the Kent Downs...

 meets non-porous London clay. Another hydrate

Hydrate

Hydrate is a term used in inorganic chemistry and organic chemistry to indicate that a substance contains water. The chemical state of the water varies widely between hydrates, some of which were so labeled before their chemical structure was understood....

 form is kieserite

Kieserite

Kieserite is a highly unstable magnesium sulfate mineral . It has a vitreous luster and it is colorless, grayish-white or yellowish. Its hardness is 3.5 and it has a monoclinic crystal system...

.

Anhydrous

Anhydrous

As a general term, a substance is said to be anhydrous if it contains no water. The way of achieving the anhydrous form differs from one substance to another...

 magnesium sulfate is used as a drying agent.