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Did you know librarians use magnesium oxide to neutralize the acidic oxidation products of old books? Or that when mixed with concrete, it creates fire-resistant wall boards for building construction? This very versatile compound is also valuable within the food industry where it is permitted in food under good manufacturing practice. Below are some magnesium oxide uses for you to consider.
Magnesium Oxide, MgO (CAS 1309-48-4), E530, is a natural, GRAS ingredient. Per CFR 21.184.1431, it is classified in two forms of white powder based on the temperature and duration of heat used in processing. Light magnesium oxide has a density of roughly 40-50 mL per 5g. Heavy magnesium oxide, which is denser at 10-20 mL per 5 g, is produced under more severe conditions. Magnesium oxide is insoluble in alcohol, achieves minimal solubility in water and has increased solubility in weak acids.
Magnesium oxide is hydroscopic. Within dry powdered formulations it acts as an anti-caking agent allowing these products to remain free-flowing. Magnesium oxide’s low water solubility may result in a white powder seen in products consumers hydrate, like powdered beverages, if the usage level is too high.
Patent US 3367784A, Gel Composition and Process, was approved in 1968 and describes a method to use magnesium oxide to create a shelf stable pectin based gel. Expanding on the ability of magnesium to increase pectin gel strength, magnesium is a key ingredient in pectin based biodegradable packaging or edible films.
Magnesium is considered an alkaline earth element. In solution magnesium oxide has a pH around 10. Per CFR 162.110, magnesium oxide can be used in an alkaline solution of 2-2.5% for cacao nip processing as part of the Dutch cocoa process which results in a mellow flavored cocoa with improved wettability, dispersibility and suspension holding properties. The Codex also indicates magnesium oxide as an approved ingredient in several dairy products like cheese.
Magnesium is a key component in chlorophyll. In the 1943 patent US 2318426A, Method of canning green vegetables, magnesium oxide is utilized within the first step of blanching, which results in the retention of a bright green color within canned peas.
Last year I discussed Magnesium as an opportunity mineral since it plays a large role within several aspects of health and diets are often lacking in this key nutrient. While other Magnesium salts may offer more bioavailability, magnesium oxide contains 55-60% magnesium and is a relatively inexpensive magnesium fortification. Magnesium oxide is used in fortification of breads, however, at too high of a usage rate will change the pH of the dough resulting in a less desirable end product. To counter flavor or pH changes, magnesium oxide is offered in encapsulated forms.
While magnesium oxide delivers an unpleasant bitter note, there are some applications for this ingredient to enhance flavors. For example, in frying oil, magnesium oxide can absorb polar lipids which results in a temporary reduction of flavor deterioration of the oil.
When magnesium oxide is mixed into water it is slightly soluble and will form magnesium hydroxide. Recent coffee flavor research showed that hard water, containing magnesium hydroxide, achieved a brewed coffee with more flavor compounds and caffeine.
Mixing magnesium oxide and water generates an exothermic reaction which has seen applications in self-heating food packaging.
Several studies have been completed around the antimicrobial effects of MgO. A Recent study by Jin and He published in 2011 in the Journal of Nanoparticle Research showed potential of Magnesium Oxide Nanoparticles (MgO NP) as a bactericide effective against Salmonella and E. coli. The MgO NP disrupts the bacteria cell structure. As a future state potentially these findings can be applied in formulations, within manufacturing as a process aid, or as a component within packaging to enable greater food safety.
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Magnesium oxide (MgO), 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 held together by ionic bonding. Magnesium hydroxide forms in the presence of water (MgO + H2O → Mg(OH)2), but it can be reversed by heating it to remove moisture.
Magnesium oxide was historically known as magnesia alba (literally, the white mineral from Magnesia), to differentiate it from magnesia nigra, a black mineral containing what is now known as manganese.
Related oxides
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While "magnesium oxide" normally refers to MgO, the compound magnesium peroxide MgO2 is also known. According to evolutionary crystal structure prediction,[11] MgO2 is thermodynamically stable at pressures above 116 GPa (gigapascals), and a semiconducting suboxide Mg3O2 is thermodynamically stable above 500 GPa. Because of its stability, MgO is used as a model system for investigating vibrational properties of crystals.[12]
Electric properties
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Pure MgO is not conductive and has a high resistance to electric current at room temperature. The pure powder of MgO has a relative permittivity inbetween 3.2 to 9.9 k {\displaystyle k} with an approximate dielectric loss of tan(δ) > 2.16x103 at 1kHz.[5][6][7]
Production
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Magnesium oxide is produced by the calcination of magnesium carbonate or magnesium hydroxide. The latter is obtained by the treatment of magnesium chloride MgCl
2 solutions, typically seawater, with limewater or milk of lime.[13]
Calcining at different temperatures produces magnesium oxide of different reactivity. High temperatures 1500 – 2000 °C diminish the available surface area and produces dead-burned (often called dead burnt) magnesia, an unreactive form used as a refractory. Calcining temperatures 1000 – 1500 °C produce hard-burned magnesia, which has limited reactivity and calcining at lower temperature, (700–1000 °C) produces light-burned magnesia, a reactive form, also known as caustic calcined magnesia. Although some decomposition of the carbonate to oxide occurs at temperatures below 700 °C, the resulting materials appear to reabsorb carbon dioxide from the air.[citation needed]
Applications
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Refractory insulator
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MgO is prized as a refractory material, i.e. a solid that is physically and chemically stable at high temperatures. It has the useful attributes of high thermal conductivity and low electrical conductivity. According to a 2006 reference book:[14]
By far the largest consumer of magnesia worldwide is the refractory industry, which consumed about 56% of the magnesia in the United States in 2004, the remaining 44% being used in agricultural, chemical, construction, environmental, and other industrial applications.
MgO is used as a refractory material for crucibles. It is also used as an insulator in heat-resistant electrical cable.
Heating elements
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It is used extensively as an electrical insulator in tubular construction heating elements as in electric stove and cooktop heating elements. There are several mesh sizes available and most commonly used ones are 40 and 80 mesh per the American Foundry Society. The extensive use is due to its high dielectric strength and average thermal conductivity. MgO is usually crushed and compacted with minimal airgaps or voids.
Cement
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MgO is one of the components in Portland cement in dry process plants.
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Sorel cement uses MgO as the main component in combination with MgCl2 and water.
Fertilizer
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MgO has an important place as a commercial plant fertilizer[15] and as animal feed.[16]
Fireproofing
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It is a principal fireproofing ingredient in construction materials. As a construction material, magnesium oxide wallboards have several attractive characteristics: fire resistance, termite resistance, moisture resistance, mold and mildew resistance, and strength, but also a severe downside as it attracts moisture and can cause moisture damage to surrounding materials [17][14][1]
Medical
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Magnesium oxide is used for relief of heartburn and indigestion, as an antacid, magnesium supplement, and as a short-term laxative. It is also used to improve symptoms of indigestion. Side effects of magnesium oxide may include nausea and cramping.[18] In quantities sufficient to obtain a laxative effect, side effects of long-term use may rarely cause enteroliths to form, resulting in bowel obstruction.[19]
Waste treatment
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Magnesium oxide is used extensively in the soil and groundwater remediation, wastewater treatment, drinking water treatment, air emissions treatment, and waste treatment industries for its acid buffering capacity and related effectiveness in stabilizing dissolved heavy metal species.[according to whom?]
Many heavy metals species, such as lead and cadmium, are least soluble in water at mildly basic conditions (pH in the range 8–11). Solubility of metals increases their undesired bioavailability and mobility in soil and groundwater. Granular MgO is often blended into metals-contaminating soil or waste material, which is also commonly of a low pH (acidic), in order to drive the pH into the 8–10 range. Metal-hydroxide complexes tend to precipitate out of aqueous solution in the pH range of 8–10.
MgO is packed in bags around transuranic waste in the disposal cells (panels) at the Waste Isolation Pilot Plant, as a CO2 getter to minimize the complexation of uranium and other actinides by carbonate ions and so to limit the solubility of radionuclides. The use of MgO is preferred over CaO since the resulting hydration product (Mg(OH)
2) is less soluble and releases less hydration heat. Another advantage is to impose a lower pH value (about 10.5) in case of accidental water ingress into the dry salt layers, in contast to the more soluble Ca(OH)
2 which would create a higher pH of 12.5 (strongly alkaline conditions). The Mg2+
cation being the second most abundant cation in seawater and in rocksalt, the potential release of magnesium ions dissolving in brines intruding the deep geological repository is also expected to minimize the geochemical disruption.[20]
Niche uses
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Unpolished MgO crystalHistorical uses
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Precautions
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Inhalation of magnesium oxide fumes can cause metal fume fever.[32]
See also
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Pages displaying wikidata descriptions as a fallback
Notes
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References
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