Magnesium sulfate

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Magnesium sulfate
Magnesium sulfate anhydrous.jpg
Anhydrous magnesium sulfate
Magnesium sulfate.JPG
Epsomite (heptahydrate)
Names
IUPAC name
Magnesium sulfate
Other names
Epsom salt (heptahydrate)
English salt
Bitter salts
Bath salts
Identifiers
7487-88-9 YesY
14168-73-1 (monohydrate) YesY
24378-31-2 (tetrahydrate) YesY
15553-21-6 (pentahydrate) YesY
13778-97-7 (hexahydrate) YesY
10034-99-8 (heptahydrate) YesY
ChEBI CHEBI:32599 YesY
ChEMBL ChEMBL1200456 N
ChemSpider 22515 YesY
DrugBank DB00653 YesY
Jmol 3D model Interactive image
PubChem 24083
RTECS number OM4500000
UNII ML30MJ2U7I YesY
  • InChI=1S/Mg.H2O4S/c;1-5(2,3)4/h;(H2,1,2,3,4)/q+2;/p-2 YesY
    Key: CSNNHWWHGAXBCP-UHFFFAOYSA-L YesY
  • InChI=1/Mg.H2O4S/c;1-5(2,3)4/h;(H2,1,2,3,4)/q+2;/p-2
    Key: CSNNHWWHGAXBCP-NUQVWONBAQ
  • [Mg+2].[O-]S([O-])(=O)=O
Properties
MgSO4
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
Odor odorless
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
anhydrous
26.9 g/100 mL (0 °C)
35.1 g/100 mL (20 °C)
50.2 g/100 mL (100 °C)
heptahydrate
71 g/100 mL (20 °C)
Solubility 1.16 g/100 mL (18°C, ether)
slightly soluble in alcohol, glycerol
insoluble in acetone
1.523 (monohydrate)
1.433 (heptahydrate)
Structure
monoclinic (hydrate)
Pharmacology
ATC code A06AD04
A12CC02 B05XA05 D11AX05 V04CC02
Vapor pressure {{{value}}}
Related compounds
Other cations
 Beryllium sulfate
Calcium sulfate
Strontium sulfate
Barium sulfate
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N verify (what is YesYN ?)
Infobox references

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.[1]

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.[2]

It is on the WHO Model List of Essential Medicines, the most important medications needed in a basic health system.[3][4]

Uses

Medical

Magnesium sulfate is a common mineral 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:

An overdose of magnesium causes hypermagnesemia.

Agriculture

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.[14] 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.[citation needed]

Other

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. It is also a common belief that magnesium sulfate can be absorbed into the skin, reducing inflammation. However, no scientific study has ever been published to either explain or reaffirm this belief.[citation needed] It is naturally present in some mineral waters.[citation needed]

It may also be used as a coagulant for making tofu.[15]

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.[16]

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.

Pregnancy usage

Magnesium sulfate was once used as a tocolytic,[17][18] but meta-analyses have failed to support it as an anti-contraction medication.[19][20] And its use for prolonged periods (more than five to seven days) may result in health problems for the baby.[21]

In those at risk of an early delivery, magnesium sulfate appears to decrease the risk of cerebral palsy.[22][23] It is unclear if it helps those who are born at term.[24]

Debate

A study carried out in February 2015 found that Epsom salt minutely raises magnesium levels in those who bathe in it regularly. Therefore, although Epsom salts may help relieve some muscle tightness, Epsom salts are less beneficial than once thought.[25]

Physical properties

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[26] (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.

Hydrates

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,[27] 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.

The pH of hydrates is average 6.0 (5.5 to 6.5). Magnesium hydrates have, like copper(II) sulfate, coordinated water.[28]

Manufacturing

The heptahydrate can be prepared by neutralizing sulfuric acid with magnesium carbonate or oxide, but it is usually obtained directly from natural sources.

Anhydrous magnesium sulfate is prepared only by the dehydration of a hydrate.

Occurrence

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.

Bright spots observed by the Dawn Spacecraft in Occator Crater on the dwarf planet Ceres are most consistent with reflected light from magnesium sulfate hexahydrate.[29]

References

  1. ↑ Industrial Inorganic Chemistry, Karl Heinz Büchel, Hans-Heinrich Moretto, Dietmar Werner, John Wiley & Sons, 2d edition, 2000, ISBN 978-3-527-61333-5
  2. ↑ 2.0 2.1 Lua error in package.lua at line 80: module 'strict' not found.
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  7. ↑ 7.0 7.1 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. doi:10.1378/chest.128.1.337 PMID 16002955.
  8. ↑ Lua error in package.lua at line 80: module 'strict' not found.
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  13. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  14. ↑ Reece, J. B., & Campbell, N. A. (2011). Campbell biology. (9th ed., p. 791). Boston: Benjamin Cummings
  15. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  16. ↑ Lua error in package.lua at line 80: module 'strict' not found.
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  21. ↑ Lua error in package.lua at line 80: module 'strict' not found.
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  26. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  27. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  28. ↑ 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
  29. ↑ Lua error in package.lua at line 80: module 'strict' not found.

External links


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