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. 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.

Chemical 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.

Physical properties

Two forms of magnesium oxide exist: a bulky form termed light magnesium oxide and a dense form termed heavy magnesium oxide. 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. It is practically insoluble in water and is insoluble in alcohol. It is soluble in dilute acids.

The Uses of Magnesium oxide

Magnesium oxide is used for:
1.Magnesium Oxide is a source of magnesium which functions as a nutrient and dietary supplement.
2.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.
3.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).
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.

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.

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.

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.

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