magnesium sulfate
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Magnesium sulfate or magnesium sulphate (in
British English British English (BrE) is the standard dialect A standard language (also standard variety, standard dialect, and standard) is a language variety that has undergone substantial codification of grammar and usage and is employed by a populatio ...
) is a
chemical compound A chemical compound is a chemical substance A chemical substance is a form of matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by having volume. All everyday objects that can be ...
, a
salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of Salt (chemistry), salts; salt in its natural form as a crystallinity, crystalline mineral is known as rock salt or halite. Sa ...
with the formula , consisting of
magnesium Magnesium is a chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the chemical elements In chemistry, an element is a pure substance consisting only of atoms that all have the same ...

magnesium
cation An ion () is an atom An atom is the smallest unit of ordinary matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by having volume. All everyday objects that can be touched are u ...
s (20.19% by mass) and
sulfate The sulfate or sulphate ion is a polyatomic anion An ion () is an atom An atom is the smallest unit of ordinary matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by having ...

sulfate
anion An ion () is an atom An atom is the smallest unit of ordinary matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by having volume. All everyday objects that can be touched are u ...
s . It is a white
crystalline solid A crystal or crystalline solid is a solid Solid is one of the four fundamental states of matter (the others being liquid, gas and plasma). The molecules in a solid are closely packed together and contain the least amount of kinet ...

crystalline solid
,
soluble Solubility is the property of a solid, liquid or gaseous chemical substance called ''solution, solute'' to dissolve in a solid, liquid or gaseous solvent. The solubility of a substance fundamentally depends on the Physical property, physical an ...

soluble
in water but not in
ethanol Ethanol (also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an . It is a simple with the C2H6O. Its formula can be also written as −− or (an linked to a group), and is often as EtOH. Ethanol is a , , ...

ethanol
. Magnesium sulfate is usually encountered in the form of a
hydrate In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science that covers the Chemical element, elements that make up matter to the chemical compound, compounds composed of atoms, m ...
, for various values of ''n'' between 1 and 11. The most common is the heptahydrate , known as Epsom salt, which is a
household chemical Household chemicals are non-food A nonfood crop, also known as industrial crop, is a crop grown to produce goods for manufacturing, for example fibre for clothing, rather than food for consumption. Purpose Industrial crops is a designation give ...
with many traditional uses, including
bath salts Bath salts are water-soluble, pulverized mineral, minerals that are added to water to be used for bathing. They are said to improve cleaning, enhance the enjoyment of bathing, and serve as a vehicle for cosmetic agents. Bath salts have been devel ...
. The main use of magnesium sulfate is in agriculture, to correct soils deficient in magnesium (an essential
plant nutrient Plant nutrition is the study of the chemical elements and Chemical compound, compounds necessary for plant growth, plant metabolism and their external supply. In its absence the plant is unable to complete a normal life cycle, or that the element i ...
because of the role of magnesium in
chlorophyll Chlorophyll (also chlorophyl) is any of several related green pigments found in the mesosomes of cyanobacteria and in the chloroplasts of algae and plants. Its name is derived from the Ancient Greek, Greek words , ("pale green") and , ("leaf") ...

chlorophyll
and
photosynthesis Photosynthesis is a process used by plants and other organisms to into that, through , can later be released to fuel the organism's activities. Some of this chemical energy is stored in molecules, such as s and es, which are synthesized fro ...

photosynthesis
). The monohydrate is favored for this use; by the mid 1970s, its production was 2.3 million tons per year. The
anhydrous A substance is anhydrous if it contains no water Water (chemical formula H2O) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the flui ...
form and several hydrates occur in nature as
mineral In geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is an Earth science concerned with the solid Earth, the rock (geology), rocks of which it is composed, and the proces ...
s, and the salt is a significant component of the water from some
springs Spring(s) may refer to: Common uses * Spring (season), a season of the year * Spring (device), a mechanical device that stores energy * Spring (hydrology), a natural source of water * Spring (mathematics), a geometric surface in the shape of a heli ...
.


Hydrates

Magnesium sulfate can
crystallize Crystallization or crystallisation is the process by which a solid forms, where the atoms or molecules are highly organized into a structure known as a crystal A crystal or crystalline solid is a solid material whose constituents (such ...

crystallize
as several
hydrate In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science that covers the Chemical element, elements that make up matter to the chemical compound, compounds composed of atoms, m ...
s, including: * Anhydrous, ; unstable in nature, hydrates to form
epsomite Epsomite is a hydrous magnesium sulfate Magnesium sulfate (Epsom Salt) or magnesium sulphate (in British English British English (BrE) is the standard dialect of the English language English is a West Germanic languages, West Ger ...

epsomite
. * Monohydrate, ;
kieserite Kieserite is the magnesium sulfate Magnesium sulfate (Epsom Salt) or magnesium sulphate (in British English British English (BrE) is the standard dialect of the English language English is a West Germanic languages, West Germanic ...
,
monoclinic In crystallography Crystallography is the experimental science of determining the arrangement of atoms in crystalline solids (see crystal structure). The word "crystallography" is derived from the Greek language, Greek words ''crystallon'' "c ...

monoclinic
. * or . * Dihydrate, ;
orthorhombic In crystallography, the orthorhombic crystal system is one of the 7 crystal systems. Orthorhombic lattices result from stretching a cubic lattice along two of its orthogonal pairs by two different factors, resulting in a rectangular prism An ...
. * or . * Trihydrate, . * Tetrahydrate, ; starkeyite, Monoclinic crystal system, monoclinic. * Pentahydrate, ; pentahydrite, triclinic. * Hexahydrate, ; hexahydrite, monoclinic. * Heptahydrate, ("Epsom salt");
epsomite Epsomite is a hydrous magnesium sulfate Magnesium sulfate (Epsom Salt) or magnesium sulphate (in British English British English (BrE) is the standard dialect of the English language English is a West Germanic languages, West Ger ...

epsomite
, orthorhombic. * Enneahydrate, , monoclinic. * Decahydrate, . * Undecahydrate, ; meridianiite, triclinic. As of 2017, the existence of the decahydrate apparently has not been confirmed. All the hydrates lose water upon heating. Above 320 °C, only the anhydrous form is stable. It decomposes without melting at 1124 °C into magnesium oxide (MgO) and sulfur trioxide (SO3).


Heptahydrate (Epsom salt)

The heptahydrate takes its common name "Epsom salt" from a bitter saline spring in Epsom in Surrey, England, where the salt was produced from the springs that arise where the Porous medium, porous chalk of the North Downs meets the Permeability (Earth sciences), impervious London Clay, London clay. The heptahydrate readily loses one equivalent of water to form the hexahydrate. It is a natural source of both magnesium and Sulfur, sulphur. Epsom salts are commonly used in
bath salts Bath salts are water-soluble, pulverized mineral, minerals that are added to water to be used for bathing. They are said to improve cleaning, enhance the enjoyment of bathing, and serve as a vehicle for cosmetic agents. Bath salts have been devel ...
, Exfoliation (cosmetology), exfoliants, muscle relaxers and pain relievers. However, these are different from Epsom salts that are used for gardening, as they contain Odor, aromas and perfumes not suitable for plants.


Monohydrate

The monohydrate can be prepared by heating the hexahydrate to approximately 150 °C. Further heating to approximately 300–320 °C gives anhydrous magnesium sulfate.


Undecahydrate

The undecahydrate , meridianiite, is stable at atmospheric pressure only below 2 °C. Above that temperature, it liquefies into a mix of solid heptahydrate and a Solubility, saturated solution. It has an eutectic point with water at −3.9 °C and 17.3% (mass) of MgSO4. Large crystals can be obtained from solutions of the proper concentration kept at 0 °C for a few days. At pressures of about 0.9 gigapascal, GPa and at 240 kelvin, K, meridianiite decomposes into a mixture of ice VI and the enneahydrate .


Enneahydrate

The enneahydrate was identified and characterized only recently, even though it seems easy to produce (by cooling a solution of and sodium sulfate in suitable proportions). The structure is monoclinic, with unit-cell parameters at 250 K: ''a'' = 0.675 nanometer, nm, ''b'' = 1.195 nm, ''c'' = 1.465 nm, β = 95.1°, ''V'' = 1.177 cubic nanometre, nm3 with ''Z'' = 4. The most probable space group is P21/c. Magnesium selenate also forms an enneahydrate , but with a different crystal structure.


Natural occurrence

As and ions are respectively the second
cation An ion () is an atom An atom is the smallest unit of ordinary matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by having volume. All everyday objects that can be touched are u ...
and the second
anion An ion () is an atom An atom is the smallest unit of ordinary matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by having volume. All everyday objects that can be touched are u ...
present in seawater after and , magnesium sulfates are common minerals in geological environments. Their occurrence is mostly connected with supergene (geology), supergene processes. Some of them are also important constituents of Evaporite, evaporitic potassium-magnesium (K-Mg) salts deposits. Bright spots observed by the Dawn Spacecraft in Occator Crater on the dwarf planet Ceres (dwarf planet), Ceres are most consistent with reflected light from magnesium sulfate hexahydrate. Almost all known mineralogical forms of MgSO4 are hydrates. Epsomite is the natural analogue of "Epsom salt". Meridianiite, MgSO4·11H2O, has been observed on the surface of frozen lakes and is thought to also occur on Mars. Hexahydrite is the next lower (6) hydrate. Three next lower hydrates—pentahydrite, starkeyite, and especially sanderite—are rare. Kieserite is a monohydrate and is common among evaporitic deposits. Anhydrous magnesium sulfate was reported from some burning Damp (mining), coal dumps.


Preparation

Magnesium sulfate is usually obtained directly from dry lake beds and other natural sources. It can also be prepared by reacting magnesite (magnesium carbonate, ) or periclase, magnesia (magnesium oxide, oxide, ) with sulfuric acid. Another possible method is to treat seawater or magnesium-containing industrial wastes so as to precipitate magnesium hydroxide and react the Precipitation (chemistry), precipitate with sulfuric acid.


Physical properties

Magnesium sulfate Relaxation (physics), relaxation is the primary mechanism that causes the absorption of Underwater acoustics, sound in seawater at Frequency, frequencies above 10 Hertz, kHz (acoustic energy is converted to thermal energy). Lower frequencies are less absorbed by the salt, so that low frequency sound travels farther in the ocean. Boric acid and magnesium carbonate also contribute to absorption.


Uses


Medical

Magnesium sulfate is used both externally (as Epsom salt) and internally. The main external use is the formulation as
bath salts Bath salts are water-soluble, pulverized mineral, minerals that are added to water to be used for bathing. They are said to improve cleaning, enhance the enjoyment of bathing, and serve as a vehicle for cosmetic agents. Bath salts have been devel ...
, especially for foot baths to soothe sore feet. Such baths have been claimed to also soothe and hasten recovery from muscle pain, soreness, or injury. Potential health effects of magnesium sulfate are reflected in medical studies on the impact of magnesium on resistant depression and as an analgesic for migraine and chronic pain. Magnesium sulfate has been studied in the treatment of asthma, Pre-eclampsia, preeclampsia and eclampsia. Magnesium sulfate is the usual component of the concentrated salt solution used in isolation tanks to increase its specific gravity to approximately 1.25–1.26. This high density allows an individual to float effortlessly on the surface of water in the closed tank, eliminating as many of the external senses as possible. In the United Kingdom, UK, a medication containing magnesium sulfate and phenol, called "drawing paste", is useful for small boils or localized infections and removing splinters. Internally, magnesium sulfate may be administered by oral, respiratory, or intravenous magnesium, intravenous routes. Internal uses include replacement therapy for magnesium deficiency, treatment of acute and severe arrhythmias, as a bronchodilator in the treatment of asthma, preventing eclampsia, a tocolytic agent, and as an anticonvulsant.


Agriculture

In agriculture, magnesium sulfate is used to increase magnesium or sulfur content in soil. It is most commonly applied to potted plants, or to magnesium-hungry crops such as potatoes, tomatoes, carrots, Capsicum, peppers, lemons, and roses. The advantage of magnesium sulfate over other magnesium soil amendments (such as Dolomite (mineral), dolomitic lime) is its high solubility, which also allows the option of foliar feeding. Solutions of magnesium sulfate are also nearly pH neutral, compared with the Alkali soil, slightly 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. Contrary to the popular belief that magnesium sulfate is able to control pests and slugs, helps seeds germination, produce more flowers, improve nutrient uptake, and is environmentally friendly, it does none of the purported claims except for correcting magnesium deficiency in soils. Magnesium sulfate can even pollute water if used in excessive amounts. Magnesium sulfate was historically used as a treatment for lead poisoning in humans prior to the development of chelation therapy, as it was hoped that any lead ingested would be precipitated out by the magnesium sulfate and subsequently purged from the Human digestive system, digestive system. This application saw particularly widespread use among veterinarians during the early-to-mid 20th century; Epsom salt was already available on many farms for agricultural use, and it was often prescribed in the treatment of farm animals that inadvertently ingested lead.


Food preparation

Magnesium sulfate is used as a brewing salt in making beer. It may also be used as a Coagulation (water treatment), coagulant for making tofu.


Chemistry

Anhydrous magnesium sulfate is commonly used as a desiccant in organic synthesis owing to its affinity for water and compatibility with most organic compounds. During work-up (chemistry), work-up, an organic phase is treated with anhydrous magnesium sulfate. The hydrated solid is then removed by filtration, decantation, or by distillation (if the boiling point is low enough). Other inorganic sulfate salts such as sodium sulfate and calcium sulfate may be used in the same way.


Construction

Magnesium sulfate is used to prepare specific cements by the reaction between magnesium oxide and magnesium sulfate solution, which are of good binding ability and more resistance than Portland cement. This cement is mainly adopted in the production of lightweight insulation panels. Weakness in water resistance limits its usage. Magnesium (or sodium) sulfate is also used for testing Construction aggregate, aggregates for soundness in accordance with ASTM International, ASTM C88 standard, when there are no service records of the material exposed to actual weathering conditions. The test is accomplished by repeated immersion in saturated solutions followed by oven drying to dehydrate the salt precipitated in permeable Porosity, pore spaces. The internal expansive force, derived from the rehydration of the salt upon re-immersion, simulates the expansion of water on freezing. Magnesium sulfate is also used to test the resistance of concrete to external sulfate attack (ESA).


Aquaria

Magnesium sulfate heptahydrate is also used to maintain the magnesium concentration in marine aquaria which contain large amounts of Scleractinia, 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 Saline water, saltwater and prevent their spontaneous Precipitation (chemistry), precipitation into calcium carbonate.


Double salts

Double salts containing magnesium sulfate exist. There are several known as sodium magnesium sulfates and Potassium magnesium sulfate (disambiguation), potassium magnesium sulfates. A mixed copper-magnesium sulfate heptahydrate (Mg,Cu)SO4·7H2O was recently found to occur in Tailings, mine tailings and has been given the mineral name alpersite.


See also

* Calcium sulfate * Magnesium chloride


References

A. Dominic Fortes, Kevin S. Knight, and Ian G. Wood (2017): "Structure, thermal expansion and incompressibility of MgSO4·9H2O, its relationship to meridianiite (MgSO4·11H2O) and possible natural occurrences". ''Acta Crystallographica Section B: Structureal Science, Crystal Engineering and Materials'', volume 73, part 1, pages 47-64. Industrial Inorganic Chemistry, Karl Heinz Büchel, Hans-Heinrich Moretto, Dietmar Werner, John Wiley & Sons, 2d edition, 2000, R. C. Peterson, W. Nelson, B. Madu, and H. F. Shurvell (2007): "Meridianiite: A new mineral species observed on Earth and predicted to exist on Mars". ''American Mineralogist'', volume 92, issue 10, pages 1756–1759. . A. Dominic Fortes, Frank Browning, and Ian G. Wood (2012): "Cation substitution in synthetic meridianiite (MgSO4·11H2O) I: X-ray powder diffraction analysis of quenched polycrystalline aggregates". ''Physics and Chemistry of Minerals'', volume 39, issue, pages 419–441.


External links


International Chemical Safety Cards—Magnesium Sulfate
{{DEFAULTSORT:Magnesium Sulfate Desiccants Laxatives Magnesium compounds Sulfates