Magnesium oxide

Description

Magnesium oxide (MgO), or magnesia, is a white hygroscopic solid mineral, often found as a powder, which occurs naturally as periclase and is a source of magnesium . It has an empirical formula of MgO and consists of a lattice of Mg2+ ions and O2? ions held together by ionic bonding. Magnesium oxide is only very slightly soluble in water but in aqueous media combines quickly with water to form magnesium hydroxide. The majority of magnesium oxide produced today is obtained from the calcination of naturally occurring minerals, magnesite, MgCO3, being the most common. Other important sources of magnesium oxide are seawater, underground deposits of brine and deep salt beds from which magnesium hydroxide [Mg(OH)2] is processed. In medicine, magnesium oxide can be used as an antacid to relieve heartburn, sour stomach, or acid indigestion, as a laxative for short-term, rapid emptying of the bowel (before surgery, for example) and as a mineral supplement used to prevent and treat low amounts of magnesium in the blood. Besides, magnesium oxide also has many nonmedicinal uses. Caustic calcined magnesia is used in a wide range of industrial applications e.g. plastics, rubber, adhesives and acid neutralization. Magnesium oxide with lower chemical activity can be used for fertilizers and animal feed. Dead-burned magnesia and finally fused magnesia can be used for a variety of refractory and electrical applications e.g. furnace lining, crucibles and fireproofing boarding.

Chemical properties

Two forms of magnesium oxide exist: a bulky form termed light magnesium oxide and a dense form termed heavy magnesium oxide. The USP 32 and JP XV define both forms in a single monograph, while the BP 2009 and PhEur 6.4 have separate monographs for each form. For the heavy variety, 15 g has an apparent volume before settling of not more than 60 mL; for the light variety, 15 g has an apparent volume before settling of not more than 100mL as defined by the BP 2009 and PhEur 6.4.
Both forms of magnesium oxide occur as fine, white, odorless powders. Magnesium oxide possesses a cubic crystal structure, though the BP 2009 and PhEur 6.4 describe the appearance of light magnesium oxide as an amorphous powder.

Chemical properties

A very bulky, white powder known as light magnesium oxide or a relatively dense, white powder known as heavy magnesium oxide. Five g of light magnesium oxide occupies a volume of approximately 40 to 50 mL, while 5 g of heavy magnesium oxide occupies a volume of approximately 10 to 20 mL. It is practically insoluble in water and is insoluble in alcohol. It is soluble in dilute acids.

Physical properties

White ceramics, with a high reflective index in the visible and near-UV regions. Used as linings in steel furnaces. Crucible container for fluoride melts. Very slowly soluble in pure water but soluble in diluted strong mineral acids. Exhibits outstanding corrosion resistance in liquid metals Mg, Li, and Na. Readily attacked by molten metals Be, Si, Ti, Zr, Nb, and Ta. MgO reacts with water, CO₂ , and diluted acids. Maximum service temperature 2400°C. Transmittance of 80% and n=1.75 in IR region 7 to 300 μm.

The Uses of Magnesium oxide

Magnesium Oxide is a source of magnesium which functions as a nutrient and dietary supplement. it exists as a bulky white powder termed light magnesium oxide or as a dense white powder known as heavy magnesium oxide. it is practically insoluble in water and is insoluble in alcohol. In industry, Magnesium oxide is used in the manufacture of refractory crucibles, refractory bricks, magnesium cements and boiler scale compounds, ‘powder’ oils, casein gum. In medicine, Magnesium oxide is used for heartburn and stomach pain relief, antacids, magnesium supplements and short-term laxatives. It is also used to improve symptoms of indigestion. Other uses include a colouring agent absorbent prior to assaying; and a moisture absorption agent for preserving books.

Indications

Indicated for over-the-counter use as a supplement for cardiovascular and neuromuscular health, and as an antacid for relief of acid indigestion and upset stomach.
Magnesium oxide, in combination with sodium picosulfate and anhydrous citric acid, is indicated for cleansing of the colon as a preparation for colonoscopy in adults and pediatric patients ages 9 years and older.

Background

Magnesium oxide is an inorganic compound that occurs in nature as the mineral periclase. In aqueous media combines quickly with water to form magnesium hydroxide. It is used as an antacid and mild laxative and has many nonmedicinal uses.

What are the applications of Application

Magnesium oxide is used for:
(1) Laboratory reagents. It is a mild alkaline reagent and can be used as a reagent for a variety of reactions such as acylation, alkylation, oxidation and reduction. It is also used as a catalyst for the dehydrogenation of n-octane to synthesise octene. As well as a good reference white for colourimetric methods.
(2) Antacid. It can be used to relieve heartburn, stomach acid or acid indigestion. Magnesium oxide is also used as a short-term laxative for rapid bowel emptying (e.g., before surgery).

Definition

Two forms are produced, one a light, fluffy material prepared by a relatively low-temperature dehydration of the hydroxide, the other a dense material made by high-temperature furnacing of the oxide after it has been formed from the carbonate or hydroxide.

Production Methods

Magnesium oxide occurs naturally as the mineral periclase. It can be manufactured by many processes. Limestone containing the mineral dolomite is calcinated at high temperatures to produce dolime, which then reacts with magnesium chloride-rich sea water to produce magnesium hydroxide and calcium chloride.The magnesium hydroxide is then calcinated to produce magnesium oxide and water. In another process, mined magnesite (MgCO₃) is calcinated to produce magnesium oxide and carbon dioxide. Purification methods include crushing and size separation, heavymedia heavymedia separation, and froth flotation. Producing magnesium oxide from sea water is a process that involves heating magnesium chloride concentrated brine from the Dead Sea. The magnesium chloride decomposes into magnesium oxide and hydrochloric acid.Magnesium oxide may also be produced by the thermal decomposition of magnesium chloride, magnesium sulfate, magnesium sulfite, nesquehonite, and the basic carbonate 5MgO·4CO₂·5H₂O. Purification of the magnesium oxide produced through thermal degradation is carried out by filtration or sedimentation.

Preparation

Magnesium oxide is easily formed by burning magnesium metal ribbon. Mg oxidizes and emits a bright white light, rich in ultraviolet and hard to extinguish. Extreme care must be taken if MgO is to be prepared by this method. Magnesia is a white solid mineral that occurs naturally as “Periclase” and is used as a source of magnesium metal. Magnesium oxide is hygroscopic in nature and care must be taken to protect it from moisture. It reacts with water and forms the hydroxide:
MgO＋H2O→Mg(OH)2
However, this reaction can be reversed by heating it to remove moisture.

General Description

Finely divided white particulate dispersed in air. (Note: Exposure may occur when magnesium is burned, thermally cut, or welded upon.).

Reactivity Profile

Phosphorus pentachloride and magnesium oxide react with brilliant incandescence [Mellor 8:1016. 1946-1947]. The oxide is incompatible with interhalogens such as bromine pentafluoride, etc.

Hazard

Toxic by inhalation of fume. Upper respiratory tract irritant, and metal fume fever. Questionable carcinogen.

Health Hazard

Magnesium oxide fume is an irritant of the eyes and nose.

Agricultural Uses

Magnesia is a term used for magnesium oxide (MgO). Magnesite, caustic-calcium magnesite, dead-burned magnesite and synthetic magnesite are also loosely used as synonyms for magnesia. Magnesium oxide is used in agricultural applications for animal feed and fertilizer; in the United States, these applications represent about 20%–25% of the total annual caustic-calcined magnesia shipment. Magnesium serves as a structural part of the chlorophyll molecule, a compound necessary for plant photosynthesis. Without sufficient magnesium, either from the soil or from fertilizer application, plants can die. Grazing ruminants, such as cattle and sheep, require magnesium in their diet to guard ag ainst hypomagnesia, also known as grass tetany, a potentially fatal disease.

Pharmaceutical Applications

Magnesium oxide is used as an alkaline diluent in solid-dosage forms to modify the pH of tablets.It can be added to solid-dosage forms to bind excess water and keep the granulation dry. In combination with silica, magnesium oxide can be used as an auxiliary glidant. It is also used as a food additive and as an antacid, either alone or in conjunction with aluminum hydroxide. Magnesium oxide is additionally used as an osmotic laxative and a magnesium supplement to treat deficiency states.

Industrial uses

Magnesium oxide (MgO) is a synthetic mineralproduced in electric arc furnaces or by sinteringof amorphous powder (periclase). Refractoryapplications consume a large quantity of MgO.Both brick and shapes are fabricated at leastpartially of sintered grain for use primarily inthe metal-processing industries. Heating unitinsulation is another major application for periclase.Principal advantages of periclase are itsthermal conductivity and electrical resistivity atelevated temperatures.
Specialty crucibles and shapes also are fabricatedfrom MgO. These are used in pyrometallurgicaland other purifying processes for specialtymetals. Both slip-casting and pressingtechniques are employed to manufactureshapes.
Thermocouple insulation comprises stillanother outlet for periclase. Since most of thesego into nuclear applications, a high-purity productis required. MgO is also an important glazeconstituent.
Single crystals of MgO have received attentionbecause of their use in ductile ceramic studies.Extreme purity is required in this area. Periclasewindows are also of potential interest ininfrared applications because of their transmissioncharacteristics.

Clinical Use

U.S. Pharmacopoeia (USP)-grade caustic-calcined  magnesia can be used in pharmaceutical applications. In the food industry, caustic-calcined magnesia is used in  sugar refining for neutralization of raw cane and beet juices and to  reduce scaling in juice heaters, evaporators, juice lines, and other  equipment.

Safety Profile

Inhalation of the fumes can produce a febrile reaction and leucocytosis in humans. Questionable carcinogen with experimental tumorigenic data. Violent reaction or ignition in contact with interhalogens (e.g., bromine pentafluoride, chlorine trifluoride), Incandescent reaction with phosphorus pentachloride. See also MAGNESIUM COMPOUNDS.

Safety

Magnesium oxide is widely used in oral formulations as an excipient and as a therapeutic agent. Therapeutically, 250–500mg is administered orally as an antacid and 2–5g as an osmotic laxative. Magnesium oxide is generally regarded as a nontoxic material when employed as an excipient, although adverse effects, due to its laxative action, may occur if high doses are ingested orally.

Potential Exposure

Used in oil refining, pulp and paper mills; tire manufacturing; in the manufacture of refractory crucibles; fire bricks; magnesia cements and boiler scale compounds. Exposure may occur when magnesium is burned, thermally cut, or welded upon.

First aid

If this chemical gets into the eyes, remove anycontact lenses at once and irrigate immediately for at least15 min, occasionally lifting upper and lower lids. Seek medical attention immediately. If this chemical contacts theskin, remove contaminated clothing and wash immediatelywith soap and water. Seek medical attention immediately. Ifthis chemical has been inhaled, remove from exposure,begin rescue breathing (using universal precautions, including resuscitation mask) if breathing has stopped and CPR ifheart action has stopped. Transfer promptly to a medicalfacility. When this chemical has been swallowed, get medical attention. Give large quantities of water and inducevomiting. Do not make an unconscious person vomit. Thesymptoms of metal fume fever may be delayed for 4°12 hfollowing exposure: it may last less than 36 h.Note to physician: In case of fume inhalation, treat for pulmonary edema. Give prednisone or other corticosteroidorally to reduce tissue response to fume. Positive-pressureventilation may be necessary. Treat metal fume fever withbed rest, analgesics, and antipyretics.

storage

Magnesium oxide is stable at normal temperatures and pressures. However, it forms magnesium hydroxide in the presence of water. Magnesium oxide is hygroscopic and rapidly absorbs water and carbon dioxide on exposure to the air, the light form more readily than the heavy form.
The bulk material should be stored in an airtight container in a cool, dry place.

Shipping

UN1418 Magnesium, powder or Magnesium alloys, powder Hazard Class: 4.3; Labels: 4.3-Dangerous when wet material, 4.2-Spontaneously combustible materia

Incompatibilities

Violent reaction with halogens/interhalogens, chlorine trifluoride, bromine pentalfluoride; strong acids. Phosphorus pentachloride and magnesium oxide react with brilliant incandescence (Mellor 8:1016. 1946
1947). May ignite and explode when heated with sublimed sulfur, magnesium powder, or aluminum powder

Incompatibilities

Magnesium oxide is a basic compound and as such can react with acidic compounds in the solid state to form salts such as Mg(ibuprofen)₂ or degrade alkaline-labile drugs.Adsorption of various drugs onto magnesium oxide has been reported, such as antihistamines, antibiotics (especially tetracyclines),salicylates, atropine sulfate,hyoscyamine hydrobromide, paracetamol, chloroquine; and anthranilic acid derivatives have been reported to adsorb onto the surface of magnesium oxide. Magnesium oxide can also complex with polymers, e.g. Eudragit RS, to retard drug release and can interact in the solid state with phenobarbitone sodium. Magnesium oxide can also reduce the bioavailability of phenytoin,trichlormethiazide,and antiarrhythmics.The presence of magnesium oxide can also have a negative impact on the solid-state chemical stability of drugs, such as diazepam.Magnesium oxide has been used as a stabilizer for omeprazole due to its strong waterproofing effect.

Regulatory Status

GRAS listed. Accepted for use as a food additive in Europe. Included in the FDA Inactive Ingredients Database (oral capsules, tablets, and buccal). Included in nonparenteral medicines licensed in the UK. Included in the Canadian List of Acceptable Non-medicinal Ingredients.

References

1. https://en.wikipedia.org/wiki/Magnesium_oxide
2. https://www.chemistryworld.com/podcasts/magnesium-oxide/7645.article
3. https://pubchem.ncbi.nlm.nih.gov/compound/magnesium_oxide#section=Top
4. http://www.azom.com/article.aspx?ArticleID=54
5. https://medlineplus.gov/druginfo/meds/a601074.html
6. https://www.merriam-webster.com/dictionary/magnesium%20oxide
7. http://www.webmd.com/drugs/2/drug-3954/magnesium-oxide-oral/details