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Magnesium oxide
Molecular Formula
MDL Number
Molecular Weight
MOL File

Chemical Properties

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.
white or light grey powder
Magnesium oxide forms a finely divided white particulate dispersed in air.
Melting point 
2852 °C (lit.)
2852 °C(lit.)

Boiling point 
3600 °C
3600 °C
refractive index 
storage temp. 
no restrictions.
5 M HCl: 0.1 M at 20 °C, clear, colorless


Specific Gravity
10.3 (H2O, 20℃)(saturated solution)
Stable. Incompatible with bromine trifluoride, bromine trichloride, phosphorus pentachloride.
Water Solubility 
6.2 mg/L (20 ºC), reacts
Air Sensitive
λ: 260 nm Amax: ≤0.040
λ: 280 nm Amax: ≤0.025
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.
CAS DataBase Reference
1309-48-4(CAS DataBase Reference)
NIST Chemistry Reference
Magnesium monoxide(1309-48-4)
EPA Substance Registry System
1309-48-4(EPA Substance)

Safety Data

Risk Statements 
R20/22:Harmful by inhalation and if swallowed .
R36/37/38:Irritating to eyes, respiratory system and skin .
Safety Statements 
S24/25:Avoid contact with skin and eyes .
UN 1418
WGK Germany 


HS Code 
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.
Hazardous Substances Data
1309-48-4(Hazardous Substances Data)

Raw materials And Preparation Products

Raw materials
Sulfuric acid -->Magnesium sulfate-->Magnesium-->Ammonium bicarbonate-->Oxygen-->Magnesium sulfate-->Magnesium carbonate-->Magnesium chloride-->Magnesium chloride hexahydrate-->Magnesium hydroxide-->BITTERN-->DOLOMITE-->Dolomite (CaMg(CO3)2), dead-burned refractory -->Magnesium carbonate basic-->Plate-and-frame filter press-->HEAVY MAGNESIUM CARBONATE
Preparation Products
naphtha steam reforming catalysts-->Gemfibrozil-->Magnesium nitrate-->5-Phenylcarbamoylamino-1,2,3-thiadiazole-->Oxendolone-->BASIC RED 29-->Magnesium stearate -->Basic Yellow 24-->Glass fiber reinforced plastic cooling tower-->7-PROPOXY-CHROMEN-2-ONE-->6-AMINO-CHROMEN-2-ONE-->8-METHOXY-2-OXO-2H-CHROMENE-3-CARBOXYLIC ACID AMIDE-->Magnesium fluorosilicate-->carnallite-->7-HYDROXY-2-OXO-2H-CHROMENE-3-CARBOXYLIC ACID AMIDE-->Magnesium carbonate basic-->zinc oxide desulphurizer-->L-Carnitine-L-tartrate -->Magnesium ascorbyl phosphate-->Magnesium fluosilicate-->7-HYDROXY-2-OXO-2H-CHROMENE-3-CARBOXYLIC ACID METHYL ESTER-->7-HYDROXY-2-OXO-2H-CHROMENE-3-CARBOXYLIC ACID METHYL ESTER-->Direct Blue 106-->6-CHLORO-2-OXO-2H-CHROMENE-3-CARBOXYLIC ACID-->BASIC RED 46-->MAGNESIUM HEXAFLUOROACETYLACETONATE DIHYDRATE-->Magnesium nitrate hexahydrate-->2,4-DINITROBENZENESULFONIC ACID-->Magnesium peroxide-->Vicnna lime-->MAGNESIUM HYDROGEN PHOSPHATE TRIHYDRATE-->2-[3-(1,3-dihydro-1,3,3-trimethyl-2H-indol-2-ylidene)prop-1-enyl]-1,3,3-trimethyl-3H-indolium chloride -->MAGNESIUM HYDROGEN ORTHOPHOSPHATE-->MAGNESIUM PHOSPHATE-->Sulfur-magnesium fertilizer-->MAGNESIUM SULFATE-->Magnesium dihydrogen di-L-aspartate-->Lycopene-->MAGNESIUM BIS(DIHYDROGEN PHOSPHATE)TETRAHYDRATE

Hazard Information

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.
Toxic by inhalation of fume. Upper respiratory tract irritant, and metal fume fever. Questionable carcinogen.
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.
UN1418 Magnesium, powder or Magnesium alloys, powder Hazard Class: 4.3; Labels: 4.3-Dangerous when wet material, 4.2-Spontaneously combustible materia
Violent reaction with halogens/interhalogens, chlorine trifluoride, bromine pentalfluoride; strong acids. Phosphorus pentachloride and magnesium oxide react with brilliant incandescence (Mellor 8:1016. 19461947). May ignite and explode when heated with sublimed sulfur, magnesium powder, or aluminum powder
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.
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:
However, this reaction can be reversed by heating it to remove moisture.
Health Hazard
Magnesium oxide fume is an irritant of the eyes and nose.
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.
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.
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.
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.
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.
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.

Material Safety Data Sheet(MSDS)

msds information

Questions and Answers (Q&A)

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.

Questions And Answer

Chemical Properties
Magnesium oxide is a typical alkaline earth metal oxide, chemical formula MgO. White powder, melting point 2852 ℃, boiling point 3600 ℃, the relative density of 3.58 (25 ℃). It is soluble in acid and ammonium salt solution. Its slow action with water can produce magnesium hydroxide. It can be dissolved in carbon dioxide aqueous solution to produce magnesium bicarbonate. In the air, it can gradually absorb moisture and carbon dioxide. Heating releases irritating fumes. Magnesite (MgCO3), dolomite (MgCO3 • CaCO3) and seawater are the main raw materials for the production of magnesium oxide.
Production of Magnesium Oxide
Thermal decomposition of magnesite or dolomite generates magnesium oxide. Magnesium hydroxide precipitate is obtained first by treating seawater with hydrated lime; magnesium oxide is obtained by burning magnesium hydroxide. Alternatively, we can take the magnesium chloride lumps or brine after bromination as raw material during the comprehensive utilization of seawater; add sodium hydroxide or sodium carbonate to generate magnesium hydroxide or basic magnesium carbonate precipitation, and then burn to obtain magnesium oxide. At present, China mainly uses magnesite, dolomite, brine or halogen as raw material.
Magnesium oxide accounts for the largest amount of magnesium compounds, accounting for about 3/4 of the total magnesium industry. Magnesia made at temperatures below 900 ° C is light magnesia with low density, having large specific surface area and strong absorbability. Can be used as a catalyst, rubber filler and improve the performance of rubber accelerator. Mixing with magnesium chloride solution can make magnesia cement. It can also be used as flame retardant for building materials. It can be medically used as antacids and laxatives for the treatment of hyperacidity and stomach and duodenal ulcer disease, often combined with calcium carbonate easy to cause constipation. For animal feed additives and plant fertilizers. The light magnesium oxide obtained at 950 ~ 1050 ℃has high density with particle distribution having a certain range and being easier to hydrate.
Use it to react with the silica on the silicon steel surface at high temperature to produce magnesium silicate film-like product; it can be used as a silicon steel separator to prevent the sintering of silicon steel upon high-temperature sintering. The heavy magnesium oxide prepared at high temperature of 1500-1800 ℃ has high density, small specific surface area, be difficult to be decomposed by heat, has low chemical activity, not easily to react with acid and low hydration rate. It can be used as high temperature refractory materials and the binder during manufacturing refractory crucible and the furnace lining.
  • Light magnesium oxide is used in ceramics, enamel, refractory crucible, refractory bricks, etc., also used as polishing agent, binder, paint and paper filler, neoprene accelerator, activator. In medicine, it can be used as antacids, laxatives, for the treatment of hyperacidity and duodenal ulcer disease, but also for glass, phenolic, plastics and other industries.
  • Dead-roasted magnesium oxide, namely magnesite, has granular type and brick type, being widely used as the refractory materials of steel furnace, cement kiln and glass furnace.
  • Alkaline granular refractory, mainly used for metal refining industry, with massive refractory for the furnace, or granular material for maintenance; Use spray, coating method to have it attached to the furnace wall in order to enhance the furnace fire resistance.
  • Magnesium oxide produce a positive charge inside the water with most of the suspended material being negatively charged, acting absorption role, can improve the filtration effect.

Industrial production of light magnesium oxide
In the salinization industry of sea salt, it is mainly used of bitter brine, heavy brine and high temperature salt as raw materials to produce light magnesium carbonate or light magnesium oxide. Industrialized production methods include soda ash method, lime and carbon ammonia.
(1) Soda ash process include: 1. Ingredients 2. Reaction 3. Washing 4. Pyrolysis 5. Filter 6.Roasting 7. Crushed packaging. Soda ash production of light magnesium carbonate or light magnesium oxide has mature technology, higher product quality. However, consumption of soda ash, fresh water consumption is also large.
(2) Lime method uses lime milk instead of soda ash. Its reaction with magnesium chloride in brine to generate magnesium hydroxide, followed by carbonation using carbon dioxide gas, generating magnesium bicarbonate. When using the lime method, the sulfate in the brine should be minimized, otherwise large deposits of calcium sulphate are formed and mixed in the product. The advantage of this method is the use of lime instead of soda ash, reducing costs. The disadvantage is that the process and equipment is more complicated than soda ash method, and by-produces large number of CaCl2 solution to be managed.
(3) Raw materials of carbon ammonia method are the high concentrations of bitter brine, brine or salt immersion thick solution. Carbon ammonia used is ammonia bicarbonate, carbonized ammonia or sending ammonia and carbon dioxide gas directly into the brine, with carbon ammonia instead of soda ash being reacted with the magnesium chloride or magnesium sulfate in the brine to generate the corresponding magnesium carbonate. The reaction is as follows:
1. Brine containing MgCl2 and MgSO4 reacts with NH4HCO3 solution: MgCl2 + 2NH4HCO3 = Mg (HCO3) 2 + 2NH4Cl MgSO4 + 2NH4HCO3 = Mg (HCO3) 2+ (NH4) 2SO4
2. Directly send ammonia and carbon dioxide to the brine.
3. The generated MgCO3 • 3H2O and Mg (HCO3) 2 are subject to pyrolysis to generate alkaline magnesium carbonate: Mg (HCO3) 2 + 2H2O = MgCO3 • 3H2O + CO2 ↑ 5 {MgCO3.3H2O} = 4MgCO3.Mg H2O + CO2 ↑ + 10H2O
4. Alkaline magnesium carbonate is roasted to generate light magnesium oxide: 4MgCO3.Mg (OH) 2.4H2O = 5MgO + 4CO2 ↑ + 5H2O
Control of carbon ammonia process: 1. Raw material concentration and reaction temperature 2. Pyrolysis temperature; 3. Dehydration, washing and drying; 4. Roasting; 5. Mother liquor treatment.
Compared with the soda ash method, the production of light magnesium carbonate and light magnesium oxide by the carbon ammonia process is simple, the product has a high specific volume, and the supply channel of the ammonium bicarbonate is more and the cost is lower. However, the mother liquor evaporation and concentration process is of high energy consumption.
Magnesium oxide is mildly irritating to the conjunctiva and nasal mucosa. Vapors can cause ulcer disease. Dust can cause breathing problems, chest pain, coughing, diffusive interstitial fibrosis and emphysema. The maximum allowable concentration in the United States is 10 mg / m3.
Usage limit
FAO / WHO (1984): milk powder 10 g / kg; cream powder 1 g / kg (both limited for vending machines).
FDA, § 184.143l, 2000: use GMP as limit.
Japan limits its usage for adsorption.
Magnesium oxide (MgO) is used as a lining for steel furnaces, as a component in ceramics, as food additives and pharmaceuticals, and to make strong window glass, fertilizers, paper, and rubber manufacturing.

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