My watch list  

Magnesium sulfate

Magnesium sulfate
IUPAC name Magnesium sulfate (anhydrous); Magnesium sulfate heptahydrate
Other names Epsom salts; bitter salts
CAS number 7487-88-9
Molecular formula MgSO4 (anhydrous);


Molar mass 120.415 g
Appearance white crystalline solid
Density 2.66g/mL, solid
Melting point

1124°C decomp.

Solubility in water 25.5 g/100 ml (20 °C)
Crystal structure monoclinic (hydrate)
Related Compounds
Other cations Calcium sulfate; Aluminium sulfate
Except where noted otherwise, data are given for
materials in their standard state
(at 25 °C, 100 kPa)

Infobox disclaimer and references

Magnesium sulfate (or sulphate) is a chemical compound containing magnesium and sulfate, with the formula MgSO4. It is often encountered as the heptahydrate, MgSO4·7H2O, commonly called Epsom salts. Anhydrous magnesium sulfate is used as a drying agent. Since the anhydrous form is hygroscopic (readily absorbs water from the air) and therefore harder to weigh accurately, the hydrate is often preferred when preparing solutions, for example in medical preparations. Epsom salts have traditionally been used as a component of bath salts.



In 1618 a farmer at Epsom in England attempted to give his cows water, but they refused to drink it due to its sour/bitter taste.[citation needed] However the farmer noticed that the water seemed to heal scratches and rashes.[citation needed] Epsom salt was originally prepared by boiling down mineral waters at Epsom, England, and later prepared from sea water.[citation needed] In modern times, these salts are obtained from certain minerals such as epsomite.[citation needed]

Agricultural use

In agriculture and gardening, magnesium sulfate is used to correct magnesium deficiency in soil (magnesium is an essential element in the chlorophyll molecule). It is most commonly applied to potted plants, or to magnesium-hungry crops, such as potatoes, roses, tomatoes, and peppers. The advantage of magnesium sulfate over other magnesium soil amendments (such as dolomitic lime) is its high solubility.

Medical use

Further information: Hypomagnesemia

Oral magnesium sulfate, or magnesium hydroxide, is commonly used as a saline laxative. Epsom salts are also available in a gel form for topical application in treating aches and pains.

Indications for its use are

  • Hypomagnesemia (low magnesium concentrations in the blood)
  • Magnesium Sulfate is the first-line antidysrhythmic agent for Torsades de pointes in cardiac arrest under the 2005 ECC guidelines.
  • As a bronchodilator after beta-agonist and anticholinergic agents have been tried, e.g. in severe exacerbations of asthma.[1] In fact, recent studies have revealed that magnesium sulfate can be nebulized to reduce the symptoms of acute asthma (Blitz et al 2005). In the UK, it is commonly administered via the intravenous route for the management of severe asthma attacks
  • Users of Epsom Salts in the gel form have reported significant and lasting reduction of pain associated with fybromyalgia and osteoporosis. [2]
  • A 2004 research study by Rosemary Waring at the School of Biosciences, Birmingham University, UK has shown that both magnesium and sulphate are absorbed through the skin when bathing in 1% solution.[3]
  • Magnesium sulfate is used to treat pre-eclampsia in laboring women
  • Magnesium sulfate can also delay labor in the case of premature labor, to delay Preterm birth
  • Solutions of sulfate salts such as Epsom salts may be given as first aid for barium poisoning
  • Magnesium sulfate paste has been used as an agent for drawing (dehydrating) boils and carbuncles.
  • Magnesium Sulfate solution has also been shown to be an effective aid in the fight against blemishes and acne when applied directly to problematic areas, usually in poultice form.

Use in organic chemistry

Anhydrous magnesium sulfate is commonly used as a desiccant in organic synthesis due to its affinity for water. During workup, an organic phase is saturated with magnesium sulfate until it no longer forms clumps. The hydrated solid is then removed with filtration or decantation.

A number of other inorganic sulfate salts, sodium sulfate and calcium sulfate for example, may also be used in the same way.

Other uses

Magnesium sulfate is used as in bath salts, particularly in flotation therapy where high concentrations raise the bath water's specific gravity, effectively making the body more buoyant. This property is also used to restore some Lava lamps damaged by being shaken by exchanging the water and adding drops of a concentrated solution until sustainable buoyancy is reached. 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 ("pruning") which is caused by prolonged immersion of extremities in pure water. However, magnesium sulfate can also be absorbed into the skin, reducing inflammation. It is also recommended for dropsy treatment for fish.[4] It may also be used as a coagulant for making tofu. Magnesium sulfate is listed as an ingredient in Dasani brand bottled water, presumably to enhance its mouth feel.


  1. ^ Blitz M, Blitz S, Hughes R, Diner B, Beasley R, Knopp J, Rowe BH. Aerosolized magnesium sulfate for acute asthma: a systematic review. Chest 2005;128:337-44. PMID 16002955.
  2. ^ Epsom Salt in gel form [1] (republished by J. Drew & Associates, with permission), 2007
  3. ^ Rosemary Waring Absorption of magnesium sulphate through the skin (republished by the Epsom Salt Council), 2004
  4. ^ Dropsy. (2004). Retrieved on 2007-05-20.
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Magnesium_sulfate". A list of authors is available in Wikipedia.
Your browser is not current. Microsoft Internet Explorer 6.0 does not support some functions on Chemie.DE