Magnesium sulfate (magnesium sulphate in British English) is a chemical compound, a salt with the formula MgSO
4, consisting of magnesium cations Mg2+
(20.19% by mass) and sulfate anions SO2−
4. It is a white crystalline solid, soluble in water but not in ethanol.
Magnesium sulfate is usually encountered in the form of a hydrate MgSO
2O, for various values of n between 1 and 11. The most common is the heptahydrate MgSO
2O, known as Epsom salt, which is a household chemical with many traditional uses, including bath salts.