Magnesium sulphate is an inorganic salt, with the chemical formula MgSO4. It occurs in two forms, monohydrate and heptahydrate. The heptahydrate form is MgSO4.7H2O and is commonly called as Epsom salt. The monohydrate is MgSO4.H2O and is present in the form of a mineral called kieserite.
Magnesium sulphate is often obtained from natural sources such as minerals in geological environments. They be formed by the supergene process, that is, their enrichment occurs relatively near the surface. Magnesium sulphate is an important constituent of evaporitic potassium-magnesium salt deposits. Magnesium sulphate monohydrate also occurs naturally as kieserite minerals.
Majority of the usage of magnesium sulphate monohydrate is in agriculture, where it is used to correct a magnesium and sulphur deficiency in the soil. Certain crops require more magnesium as it is an essential mineral in chlorophyll containing food like potato, rose, tomato, lemon tree, carrot and pepper. For such crops, magnesium sulphate monohydrate is added to the soil, as a source of extra magnesium.
Magnesium sulphate is used as an electrolyte to prepare copper sulphate. A magnesium sulphate solution is electrolyzed with a copper anode to form copper sulphate, magnesium hydroxide, and hydrogen:
Cu + MgSO4 + 2 H2O à H2 + CuSO4 + Mg(OH)2.
Magnesium sulphate is a brewing salt in beer production and is added to adjust the ion content of the brewing water and to enhance enzyme action in the mash or promote a desired flavour profile in the beer.
It is used as a coagulant in making tofu.