Magnesium sulfate heptahydrate is a hydrate that is the heptahydrate form of magnesium sulfate. It has a role as a laxative and a cathartic. It is a magnesium salt and a hydrate and contains a magnesium sulfate.

Magnesium Sulfate Monohydrate is different from Magnesium Sulfate heptahydrate. Magnesium Sulfate Monohydrate has only one crystallization water, giving it the chemical formula MgSO4. H2O, whereas Magnesium Sulfate heptahydrate contains seven water of crystallization, giving it the chemical formula MgSO4. 7H2O

The small colourless crystalline powder is used as an anticonvulsant, a cathartic, and an electrolyte replenisher in treating pre-eclampsia and eclampsia.

In addition, it was now found that magnesium sulfate heptahydrate can be used as an efficient, safe and very cheap catalyst for the condensation of 1,2-dicarbonyl compounds and o-phenylenediamine at room temperature to afford phenazine and quinoxaline derivatives in excellent yields.

In food production, Magnesium Sulfate Heptahydrate, FCC, commonly called Epsom salt, is used as a brewing salt in beer production and as a tofu coagulant. The FCC grade meets the requirements of the Food Chemical Codex and is suitable for all food, beverage and nutritional supplement applications.