Magnesium chloride

Magnesium Chloride

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Magnesium chloride

Magnesium chloride is the name for the chemical compound

Chemical compound

A chemical compound is a Chemical substance consisting of two or more different chemical element Chemical bond together in a fixed mass ratio that can be split into simpler substances....
s with the formula

Chemical formula

A chemical formula is a way of expressing information about the atoms that constitute a particular chemical compound, and how the relationship between those atoms changes in chemical reactions....
s MgCl₂ and its various hydrates MgCl₂(H₂O)_x. These salts are typical ionic halides, being highly soluble in water. The hydrated magnesium chloride can be extracted from brine

Brine

File:Kissingen-Solepumpe-1848.JPGFile:Kissingen-Solepumpe-1848-2.JPGBrine is water Saturation or nearly saturated with a Salt .It is used to preserve vegetables, fish, and meat, in a process known as brining ....
or sea water. Magnesium chloride as the natural mineral Bischofite is also extracted (solution mining) out of ancient seabeds, for example the Zechstein seabed in NW Europe or the Permian Period seabed in the central parts of the US.

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Structure, preparation, and General properties

MgCl₂ crystallizes in the cadmium chloride

Cadmium chloride

Cadmium chloride is a white crystalline compound of cadmium and chlorine, with the formula CdCl2. It is a hygroscopic solid that is highly soluble in water and slightly soluble in Ethanol....
motif, which features octahedral Mg. A variety of hydrates are known with the formula MgCl₂(H₂O)_x, and each loses water with increasing temperature: x = 12 (-16.4 °C), 8 (-3.4 °C), 6 (116.7 °C), 4 (181 °C), 2 (ca. 300 °C). In the hexahydrate, the Mg²⁺ remains octahedral

Octahedral molecular geometry

In chemistry, octahedral molecular geometry describes the shape of compounds where in six atoms or groups of atoms or ligands are symmetrically arranged around a central atom, defining the vertices of an octahedron....
, but is coordinated to six water ligand

Ligand

In chemistry, a ligand is either an atom, ion, or molecule that bonds to a central metal, generally involving formal donation of one or more of its electrons....
s.

As suggested by the existence of some hydrates, anhydrous MgCl₂ is a Lewis acid

Lewis acid

A Lewis acid is a chemical compound, A, that can accept a pair of electrons from a Lewis base, B, that acts as an electron-pair donor, forming an adduct, AB.Gilbert N....
, although a relatively weak one.

In the Dow process

Dow process

The Dow process is the electrolysis method of bromine extraction from brine, and was Herbert Henry Dow's second revolutionary process for generating bromine commercially....
, magnesium chloride is regenerated from magnesium hydroxide using hydrochloric acid

Hydrochloric acid

Hydrochloric acid is the solution of hydrogen chloride in water. It is a highly corrosive, strong acid mineral acid and has major industrial uses....
:

Mg(OH)₂

Magnesium hydroxide

Magnesium hydroxide is an inorganic compound with the chemical formula Mg2. As a suspension in water, it may be referred to as Milk of Magnesia....
(s

Solid

A solid object is in the states of matter characterized by resistance to deformation and changes of volume. In other words, it has high values both of Young's modulus and of shear modulus; this contrasts e.g....
) + 2 HCl ? MgCl₂(aq) + 2 H₂O

Water

Water is a common chemical substance that is essential for the survival of all known forms of life. In typical usage, water refers only to its liquid form or States of matter, but the substance also has a solid state, ice, and a gaseous state, water vapor or steam....
(l

Liquid

Liquid is one of the principal states of matter. A liquid is a fluid that has the particles loose and can freely form a distinct surface at the boundaries of its bulk material....
)

It can also be prepared from magnesium carbonate

Magnesium carbonate

Magnesium carbonate, MgCO3, is a white solid that occurs in nature as a mineral. Several hydrated and Base forms of magnesium carbonate also exist as minerals....
by a similar reaction.

In most of its derivatives, MgCl₂ forms octahedral complexes. Derivatives with tetrahedral Mg²⁺ are less common. Examples include salts of (tetraethylammonium

Tetraethylammonium

Tetraethylammonium is a quaternary ammonium cation consisting of four ethyl groups attached to a central nitrogen atom. Like other members of its class, it can be used to alter a compound's solubility by displacing HSAB theory with this comparatively softer acid....
)₂MgCl₄ and adduct

Adduct

An adduct is a product of a direct addition of two or more distinct molecules, resulting in a single reaction product containing all atoms of all components, with formation of two chemical bonds and a net reduction in bond multiplicity in at least one of the reactants....
s such as MgCl₂(TMEDA.

Applications

Magnesium chloride serves as precursor to other magnesium compounds, for example by precipitation:

MgCl₂(aq) + Ca(OH)₂

Calcium hydroxide

Calcium hydroxide, traditionally called slaked lime, hydrated lime, or pickling lime, is a chemical compound with the chemical formula Calcium2....
(aq) ? Mg(OH)₂

Magnesium hydroxide

Magnesium hydroxide is an inorganic compound with the chemical formula Mg2. As a suspension in water, it may be referred to as Milk of Magnesia....
(s

Solid

Calcium chloride

Calcium chloride, CaCl2, is a common Salt . It behaves as a typical ionic halide, and is solid at room temperature. It has several common applications such as brine for refrigeration plants, ice and dust control on roads, and in concrete....
(aq)

It can be electrolysed

Electrolysis

In chemistry and manufacturing, electrolysis is a method of separating Chemical bond chemical compound by passing an electric current through them....
to give magnesium

Magnesium

Magnesium is a chemical element with the symbol Mg, atomic number 12, atomic weight 24.3050 and common oxidation number +2.Magnesium, an alkaline earth metal, is the ninth most abundance of the chemical elements in the universe by mass....
metal:

MgCl₂(l

Liquid

Liquid is one of the principal states of matter. A liquid is a fluid that has the particles loose and can freely form a distinct surface at the boundaries of its bulk material....
) ? Mg(l

Liquid

Liquid is one of the principal states of matter. A liquid is a fluid that has the particles loose and can freely form a distinct surface at the boundaries of its bulk material....
) + Cl₂(g

Gas

In physics, a gas is a state of matter, consisting of a collection of particles without a definite shape or volume that are in more or less random motion....
)

This process is practiced on a substantial scale: In 1990, US production was around one million tonne

Tonne

A tonne or metric ton , also referred to as a metric tonne, is a measurement of mass equal to 1,000 kilograms, or 2204.6226 pounds....
s, with a bulk price around $180 per tonne.

The thermal dehydration of the hydrates MgCl₂(H₂O)_x (x = 6, 12) does not occur straightforwardly.

Magnesium chloride is used for a variety of other applications besides the production of magnesium

Magnesium

Paper

Paper is thin material mainly used for writing upon, printing upon or packaging. It is produced by pressing together moist fibers, typically cellulose pulp derived from wood, rags or grasses, and drying them into flexible sheets....
, fireproofing agents

Fireproofing

Fireproofing, a passive fire protection measure, refers to the act of making materials or building more resistant to fire, or to those materials themselves, or the act of applying such materials....
, cement

Cement

In the most general sense of the word, a cement is a binder, a substance which sets and hardens independently, and can bind other materials together....
s and refrigeration

Refrigeration

Refrigeration is the process of removing heat from an enclosed space, or from a substance, and moving it to a place where it is unobjectionable....
brine, and dust and erosion control. Mixed with hydrated magnesium oxide, magnesium chloride forms a hard material called Sorel cement

Sorel cement

Sorel cement is a cement#Hydraulic vs. non-hydraulic cement first produced by Frenchman Stanislas Sorel in 1867.The cement is a mixture of magnesium oxide with magnesium chloride with the approximate chemical formula Mg4Cl268, corresponding to a weight ratio of 2.5-3.5 parts MgO to one part MgCl...
. Magnesium chloride is also used as an important component in the polymerase chain reaction

Polymerase chain reaction

The polymerase chain reaction is a technique widely used in molecular biology. It derives its name from one of its key components, a DNA polymerase used to amplify a piece of DNA by in vitro enzyme DNA replication....
, a procedure used to amplify DNA fragments. Magnesium chloride is also used in several medical and topical (skin related) applications.

Culinary use

Magnesium chloride is an important coagulant used in the preparation of tofu

Tofu

Tofu , also , doufu , toufu, or bean curd , is a food of China origin, made by coagulating soy milk, and then pressing the resulting curds into blocks....
from soy milk

Soy milk

Soy milk and sometimes referred to as soy drink/beverage is a beverage made from soybeans. A stable emulsion of oil, water and protein, it is produced by soaking dry soybeans, and grinding them with water....
. In Japan it is sold as nigari (???, derived from the Japanese word for "bitter"), a white powder produced from seawater after the sodium chloride

Sodium chloride

Sodium chloride, also known as common salt, table salt, or halite, is a chemical compound with the chemical formula SodiumChlorine....
has been removed, and the water evaporated. In China it is called "lushui" (?? in Chinese). Nigari or Lushui consists mostly of magnesium chloride, with some magnesium sulfate

Magnesium sulfate

Magnesium sulfate is a chemical compound containing magnesium and sulfate, with the formula MgSO4. In its hydrated form the pH is 6.0 ....
and other trace elements. It is also an ingredient in baby formula milk.

Use as an anti-icer

A number of state highway departments throughout the United States have decreased the use of rock salt and sand on roadways and have increased the use of liquid magnesium chloride as a de-icer or anti-icer. Magnesium chloride is much less toxic to plant life surrounding highways and airports, and is less corrosive to concrete and steel (and other iron alloys) than sodium chloride. The liquid magnesium chloride is sprayed on dry pavement (tarmac) prior to precipitation or wet pavement prior to freezing temperatures in the winter months to prevent snow and ice from adhering and bonding to the roadway. The application of anti-icers is utilized in an effort to improve highway safety. Magnesium chloride is also sold in crystal form for household and business use to de-ice sidewalks and driveways. In these applications, the compound is applied after precipitation has fallen or ice has formed, instead of previously.

The use of this compound seems to show an improvement in driving conditions during and after freezing precipitation yet it seems to be negatively affecting electric utilities. Two main issues have been raised regarding the anti-icer magnesium chloride as it relates to electric utilities: contamination of insulators causing tracking and arcing across them, and corrosion of steel and aluminium

Aluminium

Aluminium or aluminum is a silvery white and ductile member of the boron group of chemical elements. It has the symbol Al; its atomic number is 13....
poles and pole hardware.

Use in dust and erosion control

Road departments and private industry may apply liquid or powdered magnesium chloride to control dust and erosion on unimproved (dirt or gravel) roads and dusty job sites such as quarries. Its hygroscopy

Hygroscopy

Hygroscopy is the ability of a substance to attract water molecules from the surrounding Natural environment through either absorption or adsorption....
makes it absorb moisture from the air, controlling the number of small particles which become airborne. Similarly, owners of indoor arenas (e.g. for horse riding) may apply magnesium chloride to sand or other floor materials to control dust.

Use in hydrogen storage

Magnesium chloride has shown promise as a storage material for hydrogen

Hydrogen

Hydrogen is the chemical element with atomic number 1. It is represented by the chemical symbol H. At standard temperature and pressure, hydrogen is a colorless, odorless, nonmetallic, tasteless, highly combustion and explosive Diatomic molecule gas with the molecular formula H2....
. Ammonia

Ammonia

Ammonia is a chemical compound with the chemical formula nitrogenhydrogen. It is normally encountered as a gas with a characteristic pungent odor....
, which is rich in hydrogen atoms, is used as an intermediate storage material. Ammonia can be effectively adsorbed onto solid magnesium chloride, forming Mg(NH₃)₆Cl₂. Ammonia is released by mild heat, and is then passed through a catalyst to give hydrogen gas.

Magnesium chloride

Structure, preparation, and General properties

Applications

Culinary use

Use as an anti-icer

Use in dust and erosion control

Use in hydrogen storage

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