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SULPHATES > Magnesium Sulfate

Magnesium sulfate is an inorganic salt containing magnesium, sulfur and oxygen, with the formula MgSO4.

Formula: MgSO4, Molar mass: 120.366 g/mol, Melting point: 1,124 °C, IUPAC ID: Magnesium sulfate, Density: 2.66 g/cm³, Soluble in: Water, Classification: Sulfates

Uses :


Magnesium sulfate is a common pharmaceutical preparation of magnesium, commonly known as Epsom salts, used both externally and internally. Epsom salts are used as bath salts. The sulfate is supplied in a gel preparation for topical application in treating aches and pains.[citation needed] Oral magnesium sulfate is commonly used as a saline laxative or osmotic purgative. Magnesium sulfate is the main preparation of intravenous magnesium.

Bathing in a 1% solution of Epsom salts (about 500g of Epsom salts for a standard size bathtub of 60 litres) is a "a safe and easy way to increase sulfate and magnesium levels in the body".

Indications for internal use are:

  •     Replacement therapy for hypomagnesemia.
  •     Magnesium sulfate is the first-line antiarrhythmic agent for torsades de pointes in cardiac arrest under the 2005 ECC guidelines and for managing quinidine-induced arrhythmias.
  •     As a bronchodilator after beta-agonist and anticholinergic agents have been tried, e.g. in severe exacerbations of asthma.[5] Studies conducted have revealed that magnesium sulfate can be nebulized to reduce the symptoms of acute asthma.[5] It is commonly administered via the intravenous route for the management of severe asthma attacks.
  •     Magnesium sulfate can be used to treat eclampsia in pregnant women.
  •     Magnesium sulfate can also delay labor by inhibiting uterine muscle contraction in the case of premature labor, to delay preterm birth.[7][8] However, meta-analyses have failed to support it as a tocolytic agent.[9][10] And its use for prolonged periods (more than 5 to 7 days) may result in health problems for the baby.
  •     Intravenous magnesium sulfate has been shown to prevent cerebral palsy in preterm babies.[12] A recent systematic review suggests that antenatal intravenous magnesium sulphate can reduce the risk of cerebral palsy and gross motor dysfunction in preterm infants by on average 30%.
  •     Magnesium sulfate has been used as an experimental treatment of Irukandji syndrome caused by envenomation by certain species of Irukandji jellyfish, however the efficacy of this treatment remains unproven.
  •     Solutions of sulfate salts such as Epsom salt may be given as first aid for barium chloride poisoning.

An overdose of magnesium causes hypermagnesemia.


In gardening and other agriculture, magnesium sulfate is used to correct a magnesium or sulfur deficiency in soil; magnesium is an essential element in the chlorophyll molecule, and sulfur is another important Macronutrient.[16] It is most commonly applied to potted plants, or to magnesium-hungry crops, such as potatoes, roses, tomatoes, lemon trees and peppers The advantage of magnesium sulfate over other magnesium soil amendments (such as dolomitic lime) is its high solubility, which also allows the option of foliar feeding. Solutions of magnesium sulfate are also nearly neutral, as compared to alkaline salts of magnesium, as found in limestone; therefore the use of magnesium sulfate as a magnesium source for soil does not significantly change the soil pH.[citation needed]


Anhydrous magnesium sulfate is commonly used as a desiccant in organic synthesis due to its affinity for water. During work-up, an organic phase is saturated with magnesium sulfate until it no longer forms clumps. The hydrated solid is then removed with filtration or decantation. Other inorganic sulfate salts such as sodium sulfate and calcium sulfate may also be used in the same way.

Magnesium sulfate is used in bath salts, particularly in flotation therapy where high concentrations raise the bath water's specific gravity, effectively making the body more buoyant. Traditionally, it is also used to prepare foot baths, intended to soothe sore feet. The reason for the inclusion of the salt is partially cosmetic: the increase in ionic strength prevents some of the temporary skin wrinkling (partial maceration) which is caused by prolonged immersion of extremities in pure water. However, magnesium sulfate can also be absorbed into the skin, reducing inflammation.[17] It is naturally present in some mineral waters.[citation needed]

It may also be used as a coagulant for making tofu.

Magnesium sulfate heptahydrate is also used to maintain the magnesium concentration in marine aquaria which contain large amounts of stony corals as it is slowly depleted in their calcification process. In a magnesium-deficient marine aquarium calcium and alkalinity concentrations are very difficult to control because not enough magnesium is present to stabilize these ions in the saltwater and prevent their spontaneous precipitation into calcium carbonate.

Magnesium sulfate is used as the electrolyte to prepare copper sulfate. A magnesium sulfate solution is electrolyzed with a copper anode to form copper sulfate, magnesium hydroxide, and hydrogen:

    Cu + MgSO4 + 2 H2O → H2 + CuSO4 + Mg(OH)2.[citation needed]

Magnesium sulfate is used as a brewing salt in beer production to adjust the ion content of the brewing water and enhance enzyme action in the mash or promote a desired flavor profile in the beer.