||This article needs more medical references for verification or relies too heavily on primary sources. (August 2014)|
Anhydrous magnesium sulfate
Epsom salt (heptahydrate)
A12 B05 D11 V04
|Molar mass||120.366 g/mol (anhydrous)
138.38 g/mol (monohydrate)
174.41 g/mol (trihydrate)
210.44 g/mol (pentahydrate)
228.46 g/mol (hexahydrate)
246.47 g/mol (heptahydrate)
|Appearance||white crystalline solid|
|Density||2.66 g/cm3 (anhydrous)
2.445 g/cm3 (monohydrate)
1.68 g/cm3 (heptahydrate)
1.512 g/cm3 (11-hydrate)
|Melting point||anhydrous decomposes at 1,124°C
monohydrate decomposes at 200°C
heptahydrate decomposes at 150°C
undecahydrate decomposes at 2°C
26.9 g/100 mL (0 °C)
35.1 g/100 mL (20 °C)
50.2 g/100 mL (100 °C)
71 g/100 mL (20 °C)
|Solubility||1.16 g/100 mL (18°C, ether)
slightly soluble in alcohol, glycerol
insoluble in acetone
Refractive index (nD)
|Crystal structure||monoclinic (hydrate)|
|EU Index||Not listed|
Except where noted otherwise, data is given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
|what is: / ?)(|
Magnesium sulfate (or magnesium sulphate) is an inorganic salt (chemical compound) containing magnesium, sulfur and oxygen, with the formula MgSO4. It is often encountered as the heptahydrate sulfate mineral epsomite (MgSO4·7H2O), commonly called Epsom salt, taking its name from a bitter saline spring in Epsom in Surrey, England, where the salt was produced from the springs that arise where the porous chalk of the North Downs meets non-porous London clay. The monohydrate, MgSO4·H2O is found as the mineral kieserite. The overall global annual usage in the mid-1970s of the monohydrate was 2.3 million tons, of which the majority was used in agriculture.
Anhydrous magnesium sulfate is used as a drying agent. The anhydrous form is hygroscopic (readily absorbs water from the air) and is therefore difficult to weigh accurately; the hydrate is often preferred when preparing solutions (for example, in medical preparations). Epsom salt has been traditionally used as a component of bath salts. Epsom salt can also be used as a beauty product. Athletes use it to soothe sore muscles, while gardeners use it to improve crops. It has a variety of other uses. Epsom salt is also effective in the removal of splinters.
Magnesium sulfate is a common pharmaceutical preparation of magnesium, commonly known as Epsom salt, used both externally and internally. Epsom salt is used as bath salts and for isolation tanks. Oral magnesium sulfate is commonly used as a saline laxative or osmotic purgative. Magnesium sulfate is the main preparation of intravenous magnesium.
Internal uses include:
- 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, magnesium sulfate can be nebulized to reduce the symptoms of acute asthma. It is commonly administered via the intravenous route for the management of severe asthma attacks.
- Magnesium sulfate is effective in decreasing the risk that pre-eclampsia progresses to eclampsia. It is also commonly used for eclampsia where compared to diazepam or phenytoin it results in better outcomes.
- In those who are at risk of a preterm birth, magnesium does not appear to be beneficial and may be harmful. A previous systematic review suggested that intravenous magnesium sulfate before birth could reduce the risk of cerebral palsy and motor dysfunction in preterm infants by 30%.
- Magnesium sulfate has been used as an experimental treatment of Irukandji syndrome caused by envenomation by certain species of Irukandji jellyfish, but 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.
- The use of Epsom salt may help "draw out" splinters.
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 micronutrient. It is most commonly applied to potted plants, or to magnesium-hungry crops, such as potatoes, roses, tomatoes, lemon trees, carrots, 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.
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. It is naturally present in some mineral waters.
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.
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.
Magnesium sulfate was once used as a tocolytic, but meta-analyses have failed to support it as an anti-contraction medication. And its use for prolonged periods (more than five to seven days) may result in health problems for the baby.
A study carried out in February 2015 found that Epsom salt only minutely raises magnesium levels in those who bathe in it regularly. According to Dr. Jordan Metlz, Epsom salt is more of a placebo than anything. Therefore, although Epsom salts may help relieve some muscle tightness, Epsom salts are less beneficial than once thought.
Magnesium sulfate is highly soluble in water. The anhydrous form is strongly hygroscopic, and can be used as a desiccant. It is the primary substance that causes the absorption of sound in seawater (acoustic energy is converted to thermal energy). Absorption is strongly dependent on frequency: lower frequencies are less absorbed by the salt, so that the sound travels much farther in the ocean. Boric acid also contributes to absorption, but the most abundant salt in seawater, sodium chloride, has negligible sound absorption.
Almost all known mineralogical forms of MgSO4 occur as hydrates. Epsomite is the natural analogue of "Epsom salt". Another heptahydrate, the copper-containing mineral alpersite (Mg,Cu)SO4·7H2O, was recently recognized. Both are, however, not the highest known hydrates of MgSO4, due to the recent terrestrial find of meridianiite, MgSO4·11H2O, which is thought to also occur on Mars. Hexahydrite is the next lower (6) hydrate. Three next lower hydrates — pentahydrite (5), starkeyite (4) and especially sanderite (2) — are more rarely found. Kieserite is a monohydrate and is common among evaporitic deposits. Anhydrous magnesium sulfate was reported from some burning coal dumps, but was never treated as a mineral.
Anhydrous magnesium sulfate is prepared only by the dehydration of a hydrate.
Magnesium sulfates are common minerals in geological environments. Their occurrence is mostly connected with supergene processes. Some of them are also important constituents of evaporitic potassium-magnesium (K-Mg) salts deposits.
- Industrial Inorganic Chemistry, Karl Heinz Büchel, Hans-Heinrich Moretto, Dietmar Werner, John Wiley & Sons, 2d edition, 2000, ISBN 978-3-527-61333-5
- "Quick Cures/Quack Cures: Is Epsom Worth Its Salt?". Wall Street Journal. April 9, 2012.
- "WHO Model List of Essential Medicines" (PDF). World Health Organization. October 2013. Retrieved 22 April 2014.
- "Pharmaceutical Information – Magnesium Sulfate". RxMed. Retrieved 2009-07-06.
- "When clicking citation, it is listed under ''Other medicinal and home uses''". Disabled-world.com. 2007-01-04. Retrieved 2009-07-06.
- 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. doi:10.1378/chest.128.1.337 PMID 16002955.
- Duley, L; Gülmezoglu, AM; Henderson-Smart, DJ; Chou, D (Nov 10, 2010). "Magnesium sulphate and other anticonvulsants for women with pre-eclampsia.". The Cochrane database of systematic reviews (11): CD000025. doi:10.1002/14651858.CD000025.pub2. PMID 21069663.
- Duley, L; Henderson-Smart, DJ; Walker, GJ; Chou, D (Dec 8, 2010). "Magnesium sulphate versus diazepam for eclampsia.". The Cochrane database of systematic reviews (12): CD000127. doi:10.1002/14651858.CD000127.pub2. PMID 21154341.
- Duley, L; Henderson-Smart, DJ; Chou, D (Oct 6, 2010). "Magnesium sulphate versus phenytoin for eclampsia.". The Cochrane database of systematic reviews (10): CD000128. doi:10.1002/14651858.CD000128.pub2. PMID 20927719.
- Doyle, LW; Crowther, CA; Middleton, P; Marret, S (Jun 2009). "Antenatal magnesium sulfate and neurologic outcome in preterm infants: a systematic review.". Obstetrics and gynecology 113 (6): 1327–33. doi:10.1097/AOG.0b013e3181a60495. PMID 19461430.
- Corkeron M (2003). "Magnesium infusion to treat Irukandji syndrome". Med J Aust 178 (8): 411. PMID 12697017.
- "BARIUM CHLORIDE DIHYDRATE 4. First Aid Measures". Jtbaker.com. Retrieved 2009-07-06.
- Reece, J. B., & Campbell, N. A. (2011). Campbell biology. (9th ed., p. 791). Boston: Benjamin Cummings
- US The present invention relates to a novel process for producing packed tofu, particularly a process for producing long-life packed tofu from sterilized soybean milk. 6042851, Matsuura, Masaru; Masaoki Sasaki & Jun Sasakib et al., "Process for producing packed tofu", published 28 Mar 2000
- "Do-It-Yourself Magnesium Supplements for the Reef Aquarium". Reefkeeping. 2006. Retrieved 2008-03-14.
- "Magnesium sulfate for preterm labor". Webmd.com. 2007-01-19. Retrieved 2009-07-06.
- Lewis DF (September 2005). "Magnesium sulfate: the first-line tocolytic". Obstet. Gynecol. Clin. North Am. 32 (3): 485–500. doi:10.1016/j.ogc.2005.03.002. PMID 16125045.
- Simhan HN, Caritis SN (2007). "Prevention of Preterm Delivery". New England Journal of Medicine 357 (5): 477–487. doi:10.1056/NEJMra050435. PMID 17671256.
- Nanda, K; Grimes, DA (2006). "Magnesium sulfate tocolysis: Time to quit". Obstetrics and Gynecology 108 (4): 986–989. doi:10.1097/01.AOG.0000236445.18265.93. PMID 17012463.
- "Magnesium Sulfate: Drug Safety Communication – Recommendation Against Prolonged Use in Pre-term Labor". FDA. Retrieved 2 June 2013.
- Doyle, LW; Crowther, CA; Middleton, P; Marret, S; Rouse, D (Jan 21, 2009). "Magnesium sulphate for women at risk of preterm birth for neuroprotection of the fetus.". The Cochrane database of systematic reviews (1): CD004661. doi:10.1002/14651858.CD004661.pub3. PMID 19160238.
- Wolf, HT; Hegaard, HK; Greisen, G; Huusom, L; Hedegaard, M (Feb 2012). "Treatment with magnesium sulphate in pre-term birth: a systematic review and meta-analysis of observational studies.". Journal of obstetrics and gynaecology : the journal of the Institute of Obstetrics and Gynaecology 32 (2): 135–40. doi:10.3109/01443615.2011.638999. PMID 22296422.
- Nguyen, TM; Crowther, CA; Wilkinson, D; Bain, E (Feb 28, 2013). "Magnesium sulphate for women at term for neuroprotection of the fetus.". The Cochrane database of systematic reviews 2: CD009395. doi:10.1002/14651858.cd009395.pub2. PMID 23450601.
- Shea, Molly (March 10, 2015). "Can Soaking In Epsom Salt Help You De-stress—And Detox?". Yahoo. Retrieved March 12, 2015.
- "Underlying physics and mechanisms for the absorption of sound in seawater". Resource.npl.co.uk. Retrieved 2009-07-06.
- Peterson, Ronald C.; Hammarstrom, Jane M.; Seal, II, Robert R (Feb 2006). "Alpersite (Mg,Cu)SO4·7H2O, a new mineral of the melanterite group, and cuprian pentahydrite: Their occurrence within mine waste". American Mineralogist 91 (2–3): 261–269. doi:10.2138/am.2006.1911.
- Lucia Odochian "Study of the nature of the crystallization water in some magnesium hydrates by thermal methods," J. of Thermal Analysis and Calorimetry, Volume 45, Number 6, December, 1995. doi:10.1007/BF02547437
|Salts and the ester of the Sulfate ion|