Magnesium sulfate or magnesium sulphate (in English-speaking countries other than the US) is a

chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one element ...

, a

salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of salts; salt in the form of a natural crystalline mineral is known as rock salt or halite. Salt is present in vast quant ...

with the formula , consisting of

magnesium Magnesium is a chemical element with the symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 of the periodic ta ...

cations (20.19% by mass) and

sulfate The sulfate or sulphate ion is a polyatomic anion with the empirical formula . Salts, acid derivatives, and peroxides of sulfate are widely used in industry. Sulfates occur widely in everyday life. Sulfates are salts of sulfuric acid and many ...

anion An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by conve ...

s . It is a white

crystalline solid A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macros ...

soluble In chemistry, solubility is the ability of a substance, the solute, to form a solution with another substance, the solvent. Insolubility is the opposite property, the inability of the solute to form such a solution. The extent of the solubi ...

in water but not in

ethanol Ethanol (abbr. EtOH; also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound. It is an Alcohol (chemistry), alcohol with the chemical formula . Its formula can be also written as or (an ethyl ...

. Magnesium sulfate is usually encountered in the form of a hydrate , 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 chemicals that are commonly found and used in and around the average household. They are a type of consumer goods, designed particularly to assist cleaning, house and yard maintenance, cooking, pest control and ge ...

with many traditional uses, including

bath salts Bath salts are water-soluble, pulverized 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 developed wh ...

. 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 compounds necessary for plant growth and reproduction, 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 and

photosynthesis Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that, through cellular respiration, can later be released to fuel the organism's activities. Some of this chemical energy is stored i ...

). The monohydrate is favored for this use; by the mid 1970s, its production was 2.3 million tons per year. The anhydrous form and several hydrates occur in nature as

mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2 ...

s, and the salt is a significant component of the water from some springs.

Hydrates

Magnesium sulfate can

crystallize Crystallization is the process by which solid forms, where the atoms or molecules are highly organized into a structure known as a crystal. Some ways by which crystals form are precipitating from a solution, freezing, or more rarely deposi ...

as several hydrates, including: * Anhydrous, ; unstable in nature, hydrates to form

epsomite Epsomite, Epsom salt, or magnesium sulfate heptahydrate, is a hydrous magnesium sulfate mineral with formula MgSO4·7H2O. Epsomite crystallizes in the orthorhombic system as rarely found acicular or fibrous crystals, the normal form is as massiv ...

. * Monohydrate, ;

kieserite Kieserite, or magnesium sulfate monohydrate, is a hydrous magnesium sulfate mineral with formula (MgSO4·H2O). It has a vitreous luster and it is colorless, grayish-white or yellowish. Its hardness is 3.5 and crystallizes in the monoclinic cry ...

monoclinic In crystallography, the monoclinic crystal system is one of the seven crystal systems. A crystal system is described by three vectors. In the monoclinic system, the crystal is described by vectors of unequal lengths, as in the orthorhombic s ...

. * Monohydrate, ;

triclinic 180px, Triclinic (a ≠ b ≠ c and α ≠ β ≠ γ ) In crystallography, the triclinic (or anorthic) crystal system is one of the 7 crystal systems. A crystal system is described by three basis vectors. In the triclinic system, the crystal i ...

. * or . * Dihydrate, ; orthorhombic. * or . * Trihydrate, . * Tetrahydrate, ; starkeyite,

. * Pentahydrate, ; pentahydrite,

. * Hexahydrate, ; hexahydrite, monoclinic. * Heptahydrate, ("Epsom salt");

, orthorhombic. * Enneahydrate, , monoclinic. * Decahydrate, . * Undecahydrate, ;

meridianiite Meridianiite is the mineral consisting of magnesium sulfate undecahydrate, . It is colorless transparent crystalline salt that precipitates from solutions saturated in Mg2+ and SO42− ions at temperatures less than 2 °C. The synthetic com ...

, 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 Melting, or fusion, is a physical process that results in the phase transition of a substance from a solid to a liquid. This occurs when the internal energy of the solid increases, typically by the application of heat or pressure, which inc ...

at 1124 °C into

magnesium oxide Magnesium oxide ( Mg O), or magnesia, is a white hygroscopic solid mineral that occurs naturally as periclase and is a source of magnesium (see also oxide). It has an empirical formula of MgO and consists of a lattice of Mg2+ ions and O2− ions ...

(MgO) and sulfur trioxide ().

Heptahydrate

The heptahydrate takes its common name "Epsom salt" from a bitter saline spring in

Epsom Epsom is the principal town of the Borough of Epsom and Ewell in Surrey, England, about south of central London. The town is first recorded as ''Ebesham'' in the 10th century and its name probably derives from that of a Saxon landowner. The ...

Surrey Surrey () is a ceremonial and non-metropolitan county in South East England, bordering Greater London to the south west. Surrey has a large rural area, and several significant urban areas which form part of the Greater London Built-up Area. ...

, England, where the salt was produced from the springs that arise where the

porous Porosity or void fraction is a measure of the void (i.e. "empty") spaces in a material, and is a fraction of the volume of voids over the total volume, between 0 and 1, or as a percentage between 0% and 100%. Strictly speaking, some tests measure ...

chalk Chalk is a soft, white, porous, sedimentary carbonate rock. It is a form of limestone composed of the mineral calcite and originally formed deep under the sea by the compression of microscopic plankton that had settled to the sea floor. Ch ...

of the

North Downs The North Downs are a ridge of chalk hills in south east England that stretch from Farnham in Surrey to the White Cliffs of Dover in Kent. Much of the North Downs comprises two Areas of Outstanding Natural Beauty (AONBs): the Surrey Hills a ...

meets the impervious

London clay The London Clay Formation is a marine geological formation of Ypresian (early Eocene Epoch, c. 56–49 million years ago) age which crops out in the southeast of England. The London Clay is well known for its fossil content. The fossils from t ...

. The heptahydrate readily loses one equivalent of water to form the hexahydrate. It is a natural source of both magnesium and sulphur. Epsom salts are commonly used in

, exfoliants, muscle relaxers and pain relievers. However, these are different from Epsom salts that are used for gardening, as they contain aromas and

perfume Perfume (, ; french: parfum) is a mixture of fragrant essential oils or aroma compounds (fragrances), fixatives and solvents, usually in liquid form, used to give the human body, animals, food, objects, and living-spaces an agreeable scent. Th ...

s not suitable for plants.

Monohydrate

Magnesium sulfate monohydrate, or kieserite, can be prepared by heating the heptahydrate to 120 °C. Further heating to 250 °C gives anhydrous magnesium sulfate. Kieserite exhibits monoclinic symmetry at pressures lower than 2.7 GPa after which it transforms to phase of triclinic symmetry.

Undecahydrate

The undecahydrate ,

, is stable at

atmospheric pressure Atmospheric pressure, also known as barometric pressure (after the barometer), is the pressure within the atmosphere of Earth. The standard atmosphere (symbol: atm) is a unit of pressure defined as , which is equivalent to 1013.25 millibars, ...

only below 2 °C. Above that temperature, it liquefies into a mix of solid heptahydrate and a saturated solution. It has a eutectic point with water at −3.9 °C and 17.3% (mass) of . Large

crystal A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macro ...

s can be obtained from solutions of the proper concentration kept at 0 °C for a few days. At pressures of about 0.9

GPa Grading in education is the process of applying standardized measurements for varying levels of achievements in a course. Grades can be assigned as letters (usually A through F), as a range (for example, 1 to 6), as a percentage, or as a numbe ...

and at 240 K, meridianiite decomposes into a mixture of

ice VI Ice VI is a form of ice that exists at high pressure at the order of about 1 GPa (= 10 000 bar) and temperatures ranging from 130 up to 355 Kelvin (−143 °C up to 82 °C); see also the phase diagram of water. Its discovery and ...

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 nm, ''b'' = 1.195 nm, ''c'' = 1.465 nm, β = 95.1°, ''V'' = 1.177 nm³ with ''Z'' = 4. The most probable space group is P21/c.

Magnesium selenate Magnesium is a chemical element with the Symbol (chemistry), symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group ...

also forms an enneahydrate , but with a different crystal structure.

Natural occurrence

As and ions are respectively the second cation and the second

present in

seawater Seawater, or salt water, is water from a sea or ocean. On average, seawater in the world's oceans has a salinity of about 3.5% (35 g/L, 35 ppt, 600 mM). This means that every kilogram (roughly one liter by volume) of seawater has appr ...

after and , 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 Potassium is the chemical element with the symbol K (from Neo-Latin ''kalium'') and atomic number19. Potassium is a silvery-white metal that is soft enough to be cut with a knife with little force. Potassium metal reacts rapidly with atmosph ...

-magnesium (K-Mg) salts deposits. Bright spots observed by the Dawn Spacecraft in

Occator Crater Occator is an impact crater located on Ceres, the largest object in the main asteroid belt that lies between the orbits of Mars and Jupiter, that contains "Spot 5", the brightest of the bright spots observed by the Dawn spacecraft. It was kn ...

on the

dwarf planet A dwarf planet is a small planetary-mass object that is in direct orbit of the Sun, smaller than any of the eight classical planets but still a world in its own right. The prototypical dwarf planet is Pluto. The interest of dwarf planets to ...

Ceres Ceres most commonly refers to: * Ceres (dwarf planet), the largest asteroid * Ceres (mythology), the Roman goddess of agriculture Ceres may also refer to: Places Brazil * Ceres, Goiás, Brazil * Ceres Microregion, in north-central Goiás ...

are most consistent with reflected light from magnesium sulfate hexahydrate. Almost all known mineralogical forms of are hydrates.

Epsomite Epsomite, Epsom salt, or magnesium sulfate heptahydrate, is a hydrous magnesium sulfate mineral with formula MgSO4·7H2O. Epsomite crystallizes in the orthorhombic system as rarely found acicular or fibrous crystals, the normal form is as massiv ...

is the natural analogue of "Epsom salt".

Meridianiite Meridianiite is the mineral consisting of magnesium sulfate undecahydrate, . It is colorless transparent crystalline salt that precipitates from solutions saturated in Mg2+ and SO42− ions at temperatures less than 2 °C. The synthetic com ...

, , has been observed on the surface of frozen lakes and is thought to also occur on Mars.

Hexahydrite Magnesium sulfate or magnesium sulphate (in English-speaking countries other than the US) is a chemical compound, a salt with the formula , consisting of magnesium cations (20.19% by mass) and sulfate anions . It is a white crystalline solid, s ...

is the next lower hydrate. Three next lower hydrates – pentahydrite, starkeyite, and especially sanderite – are rare.

Kieserite Kieserite, or magnesium sulfate monohydrate, is a hydrous magnesium sulfate mineral with formula (MgSO4·H2O). It has a vitreous luster and it is colorless, grayish-white or yellowish. Its hardness is 3.5 and crystallizes in the monoclinic cry ...

is a monohydrate and is common among evaporitic deposits. Anhydrous magnesium sulfate was reported from some burning 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 magnesia ( oxide, MgO) with sulfuric acid (). Another possible method is to treat seawater or magnesium-containing industrial wastes so as to precipitate

magnesium hydroxide Magnesium hydroxide is the inorganic compound with the chemical formula Mg(OH)2. It occurs in nature as the mineral brucite. It is a white solid with low solubility in water (). Magnesium hydroxide is a common component of antacids, such as milk ...

and react the

precipitate In an aqueous solution, precipitation is the process of transforming a dissolved substance into an insoluble solid from a super-saturated solution. The solid formed is called the precipitate. In case of an inorganic chemical reaction leading ...

with sulfuric acid. Also, magnesium sulfate heptahydrate (

, ) is manufactured by dissolution of magnesium sulfate monohydrate (

, ) in water and subsequent crystallization of the heptahydrate.

Physical properties

Magnesium sulfate relaxation is the primary mechanism that causes the absorption of

sound In physics, sound is a vibration that propagates as an acoustic wave, through a transmission medium such as a gas, liquid or solid. In human physiology and psychology, sound is the ''reception'' of such waves and their ''perception'' by the ...

at frequencies above 10

kHz The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose expression in terms of SI base units is s−1, meaning that on ...

(

acoustic energy In physics, sound is a vibration that propagates as an acoustic wave, through a transmission medium such as a gas, liquid or solid. In human physiology and psychology, sound is the ''reception'' of such waves and their ''perception'' by the ...

is converted to

thermal energy The term "thermal energy" is used loosely in various contexts in physics and engineering. It can refer to several different well-defined physical concepts. These include the internal energy or enthalpy of a body of matter and radiation; heat, de ...

). Lower frequencies are less absorbed by the salt, so that low frequency sound travels farther in the ocean.

Boric acid Boric acid, more specifically orthoboric acid, is a compound of boron, oxygen, and hydrogen with formula . It may also be called hydrogen borate or boracic acid. It is usually encountered as colorless crystals or a white powder, that dissolve ...

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

, especially for

foot bath An is a Japanese public bath Public baths originated when most people in population centers did not have access to private bathing facilities. Though termed "public", they have often been restricted according to gender, religious affiliation, p ...

s 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 Asthma is a long-term inflammatory disease of the airways of the lungs. It is characterized by variable and recurring symptoms, reversible airflow obstruction, and easily triggered bronchospasms. Symptoms include episodes of wheezing, co ...

preeclampsia Pre-eclampsia is a disorder of pregnancy characterized by the onset of high blood pressure and often a significant amount of protein in the urine. When it arises, the condition begins after 20 weeks of pregnancy. In severe cases of the disease ...

and

eclampsia Eclampsia is the onset of seizures (convulsions) in a woman with pre-eclampsia. Pre-eclampsia is one of the hypertensive disorders of pregnancy that presents with three main features: new onset of high blood pressure, large amounts of protein in ...

. Magnesium sulfate is the usual component of the concentrated salt solution used in

isolation tank An isolation tank, sensory deprivation tank, float tank, float pod, float cabin, flotation tank, or sensory attenuation tank is a water filled, pitch-black, light-proof, soundproof environment heated to the same temperature as the skin, developed ...

s to increase its

specific gravity Relative density, or specific gravity, is the ratio of the density (mass of a unit volume) of a substance to the density of a given reference material. Specific gravity for liquids is nearly always measured with respect to water at its densest ...

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 UK, a medication containing magnesium sulfate and

phenol Phenol (also called carbolic acid) is an aromatic organic compound with the molecular formula . It is a white crystalline solid that is volatile. The molecule consists of a phenyl group () bonded to a hydroxy group (). Mildly acidic, it ...

, 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 routes. Internal uses include replacement therapy for

magnesium deficiency Magnesium deficiency is an electrolyte disturbance in which there is a low level of magnesium in the body. It can result in multiple symptoms. Symptoms include tremor, poor coordination, muscle spasms, loss of appetite, personality changes, an ...

, treatment of acute and severe arrhythmias, as a

bronchodilator A bronchodilator or broncholytic (although the latter occasionally includes secretory inhibition as well) is a substance that dilates the bronchi and bronchioles, decreasing resistance in the respiratory airway and increasing airflow to the lung ...

in the treatment of

, preventing

, a

tocolytic Tocolytics (also called anti-contraction medications or labor suppressants) are medications used to suppress premature labor (from Greek τόκος ''tókos'', "childbirth", and λύσις ''lúsis'', "loosening"). Preterm birth accounts for 70% ...

agent, and as an anticonvulsant. It also may be used as

laxative Laxatives, purgatives, or aperients are substances that loosen stools and increase bowel movements. They are used to treat and prevent constipation. Laxatives vary as to how they work and the side effects they may have. Certain stimulant, lubri ...

Agriculture

agriculture Agriculture or farming is the practice of cultivating plants and livestock. Agriculture was the key development in the rise of sedentary human civilization, whereby farming of domesticated species created food surpluses that enabled people to ...

, magnesium sulfate is used to increase magnesium or sulfur content in

soil Soil, also commonly referred to as earth or dirt Dirt is an unclean matter, especially when in contact with a person's clothes, skin, or possessions. In such cases, they are said to become dirty. Common types of dirt include: * Debri ...

. It is most commonly applied to potted plants, or to magnesium-hungry crops such as

potato The potato is a starchy food, a tuber of the plant ''Solanum tuberosum'' and is a root vegetable native to the Americas. The plant is a perennial in the nightshade family Solanaceae. Wild potato species can be found from the southern Unit ...

es,

tomato The tomato is the edible berry of the plant ''Solanum lycopersicum'', commonly known as the tomato plant. The species originated in western South America, Mexico, and Central America. The Mexican Nahuatl word gave rise to the Spanish word ...

es, carrots,

peppers Pepper or peppers may refer to: Food and spice * Piperaceae or the pepper family, a large family of flowering plant ** Black pepper * ''Capsicum'' or pepper, a genus of flowering plants in the nightshade family Solanaceae ** Bell pepper ** Chili ...

lemons The lemon (''Citrus limon'') is a species of small evergreen trees in the flowering plant family Rutaceae, native to Asia, primarily Northeast India (Assam), Northern Myanmar or China. The tree's ellipsoidal yellow fruit is used for culina ...

, and

rose A rose is either a woody perennial flowering plant of the genus ''Rosa'' (), in the family Rosaceae (), or the flower it bears. There are over three hundred species and tens of thousands of cultivars. They form a group of plants that can be ...

s. The advantage of magnesium sulfate over other magnesium soil amendments (such as dolomitic lime) is its high

solubility In chemistry, solubility is the ability of a substance, the solute, to form a solution with another substance, the solvent. Insolubility is the opposite property, the inability of the solute to form such a solution. The extent of the solubil ...

, which also allows the option of

foliar feeding Foliar feeding is a technique of feeding plants by applying liquid fertilizer directly to the leaves. Plants are able to absorb essential elements through their leaves. The absorption takes place through their stomata and also through their epidermi ...

. Solutions of magnesium sulfate are also nearly pH neutral, compared with the slightly alkaline salts of magnesium as found in

limestone Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms whe ...

; 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 prior to the development of

chelation therapy Chelation therapy is a medical procedure that involves the administration of chelating agents to remove heavy metals from the body. Chelation therapy has a long history of use in clinical toxicology and remains in use for some very specific me ...

, as it was hoped that any lead ingested would be precipitated out by the magnesium sulfate and subsequently purged from the 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 * Brewing salt in making

beer Beer is one of the oldest and the most widely consumed type of alcoholic drink in the world, and the third most popular drink overall after water and tea. It is produced by the brewing and fermentation of starches, mainly derived from ce ...

. * coagulant for making

tofu Tofu (), also known as bean curd in English, is a food prepared by coagulating soy milk and then pressing the resulting curds into solid white blocks of varying softness; it can be ''silken'', ''soft'', ''firm'', ''extra firm'' or ''super f ...

. *

Salt substitute A salt substitute, also known as low-sodium salt, is a low-sodium alternative to edible salt (table salt) marketed to circumvent the risk of high blood pressure and cardiovascular disease associated with a high intake of sodium chloride while main ...

Chemistry

Anhydrous magnesium sulfate is commonly used as a desiccant in organic synthesis owing to its affinity for

water Water (chemical formula ) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living organisms (in which it acts as a ...

and compatibility with most organic compounds. During work-up, an organic phase is treated with anhydrous magnesium sulfate. The hydrated solid is then removed by filtration,

decantation Decantation is a process for the separation of mixtures of immiscible liquids or of a liquid and a solid mixture such as a suspension. The layer closer to the top of the container—the less dense of the two liquids, or the liquid from which t ...

, or by

distillation Distillation, or classical distillation, is the process of separating the components or substances from a liquid mixture by using selective boiling and condensation, usually inside an apparatus known as a still. Dry distillation is the heat ...

(if the boiling point is low enough). Other inorganic sulfate salts such as sodium sulfate and

calcium sulfate Calcium sulfate (or calcium sulphate) is the inorganic compound with the formula CaSO4 and related hydrates. In the form of γ-anhydrite (the anhydrous form), it is used as a desiccant. One particular hydrate is better known as plaster of Paris ...

may be used in the same way.

Construction

Magnesium sulfate is used to prepare specific

cement A cement is a binder, a chemical substance used for construction that sets, hardens, and adheres to other materials to bind them together. Cement is seldom used on its own, but rather to bind sand and gravel ( aggregate) together. Cement mi ...

s by the reaction between

and magnesium sulfate solution, which are of good binding ability and more resistance than

Portland cement Portland cement is the most common type of cement in general use around the world as a basic ingredient of concrete, mortar, stucco, and non-specialty grout. It was developed from other types of hydraulic lime in England in the early 19th ...

. 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 aggregates for soundness in accordance with ASTM C88 standard, when there are no service records of the material exposed to actual

weathering Weathering is the deterioration of rocks, soils and minerals as well as wood and artificial materials through contact with water, atmospheric gases, and biological organisms. Weathering occurs ''in situ'' (on site, with little or no movement), ...

conditions. The test is accomplished by repeated immersion in saturated solutions followed by oven drying to dehydrate the salt precipitated in permeable pore spaces. The internal expansive force, derived from the rehydration of the salt upon re-immersion, simulates the expansion of water on

freezing Freezing is a phase transition where a liquid turns into a solid when its temperature is lowered below its freezing point. In accordance with the internationally established definition, freezing means the solidification phase change of a liquid ...

. Magnesium sulfate is also used to test the resistance of

concrete Concrete is a composite material composed of fine and coarse aggregate bonded together with a fluid cement (cement paste) that hardens (cures) over time. Concrete is the second-most-used substance in the world after water, and is the most wid ...

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 stony corals, as it is slowly depleted in their

calcification Calcification is the accumulation of calcium salts in a body tissue. It normally occurs in the formation of bone, but calcium can be deposited abnormally in soft tissue,Miller, J. D. Cardiovascular calcification: Orbicular origins. ''Nature Ma ...

process. In a magnesium-deficient marine aquarium, calcium and

alkalinity Alkalinity (from ar, القلوي, al-qaly, lit=ashes of the saltwort) is the capacity of water to resist acidification. It should not be confused with basicity, which is an absolute measurement on the pH scale. Alkalinity is the strength ...

concentrations are very difficult to control because not enough magnesium is present to stabilize these ions in the

saltwater Saline water (more commonly known as salt water) is water that contains a high concentration of dissolved salts (mainly sodium chloride). On the United States Geological Survey (USGS) salinity scale, saline water is saltier than brackish water, ...

and prevent their spontaneous

precipitation In meteorology, precipitation is any product of the condensation of atmospheric water vapor that falls under gravitational pull from clouds. The main forms of precipitation include drizzle, rain, sleet, snow, ice pellets, graupel and hail. ...

into calcium carbonate.

Double salts

Double salts A double salt is a salt that contains two or more different cations or anions. Examples of double salts include alums (with the general formula ) and Tutton's salts (with the general formula ). Other examples include potassium sodium tartrate, am ...

containing magnesium sulfate exist. There are several known as sodium magnesium sulfates and potassium magnesium sulfates. A mixed

copper Copper is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkis ...

-magnesium sulfate heptahydrate was recently found to occur in

mine tailings In mining, tailings are the materials left over after the process of separating the valuable fraction from the uneconomic fraction (gangue) of an ore. Tailings are different to overburden, which is the waste rock or other material that overl ...

and has been given the mineral name

alpersite Alpersite ( IMA symbol: Aps) is a magnesium copper sulfate mineral The sulfate minerals are a class of minerals that include the sulfate ion () within their structure. The sulfate minerals occur commonly in primary evaporite depositional envi ...

Research

Research on

topical A topical medication is a medication that is applied to a particular place on or in the body. Most often topical medication means application to body surfaces such as the skin or mucous membranes to treat ailments via a large range of classes ...

magnesium (for example

epsom salt Epsomite, Epsom salt, or magnesium sulfate heptahydrate, is a hydrous magnesium sulfate mineral with formula MgSO4·7H2O. Epsomite crystallizes in the orthorhombic system as rarely found acicular or fibrous crystals, the normal form is as massi ...

baths) is very limited. The Epsom Salt Council recommends bathing 2 or 3 times/ week, using 500-600g

Epsom salt Epsomite, Epsom salt, or magnesium sulfate heptahydrate, is a hydrous magnesium sulfate mineral with formula MgSO4·7H2O. Epsomite crystallizes in the orthorhombic system as rarely found acicular or fibrous crystals, the normal form is as massi ...

s each time.

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