Anhydrous magnesium sulfate
Epsom salt (heptahydrate)
3D model (Jmol)
|E number||E518 (acidity regulators, ...)|
|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)
|A06AD04 (WHO) A12CC02 (WHO) B05XA05 (WHO) D11AX05 (WHO) V04CC02 (WHO)|
|Safety data sheet||External MSDS|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
|what is ?)(|
Magnesium sulfate 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. 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: for example, Epsom salt is also effective in the removal of splinters.
Magnesium sulfate is a common mineral pharmaceutical preparation of magnesium, commonly known as Epsom salt, used both externally and internally. Magnesium sulfate is highly water-soluble and solubility is inhibited with lipids typically used in lotions. Lotions often employ the use of emulsions or suspensions to include both oil and water-soluble ingredients. Hence, magnesium sulfate in a lotion may not be as freely available to migrate to the skin nor to be absorbed through the skin, hence both studies may properly suggest absorption or lack thereof as a function of the carrier (in a water solution vs. in an oil emulsion/suspension). Temperature and concentration gradients may also be contributing factors to absorption.
Internal uses include:
- Oral magnesium sulfate is commonly used as a saline laxative or osmotic purgative.
- Replacement therapy for hypomagnesemia
- Magnesium sulfate is a antiarrhythmic agent for torsades de pointes in cardiac arrest under the 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. IV magnesium sulfate is used to prevent and treat seizures of eclampsia. It reduces the systolic blood pressure but doesn't alter the diastolic blood pressure, so the blood perfusion to the fetus isn't compromised. It is also commonly used for eclampsia where compared to diazepam or phenytoin it results in better outcomes.
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, compared with 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.
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.
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 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 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.
It is often encountered as the heptahydrate sulfate mineral epsomite (MgSO4·7H2O), commonly called Epsom salt, which takes 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.
- 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.
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- "CPR and First Aid: Antiarrhythmic Drugs During and Immediately After Cardiac Arrest (section)". American Heart Association. Retrieved 29 August 2016.
Previous ACLS guidelines addressed the use of magnesium in cardiac arrest with polymorphic ventricular tachycardia (ie, torsades de pointes) or suspected hypomagnesemia, and this has not been reevaluated in the 2015 Guidelines Update. These previous guidelines recommended defibrillation for termination of polymorphic VT (ie, torsades de pointes), followed by consideration of intravenous magnesium sulfate when secondary to a long QT interval.
- 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.
- Reece, J. B., & Campbell, N. A. (2011). Campbell biology. (9th ed., p. 791). Boston: Benjamin Cummings
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- "Do-It-Yourself Magnesium Supplements for the Reef Aquarium". Reefkeeping. 2006. Retrieved 2008-03-14.
- "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
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Salts and esters of the sulfate ion