Magnesium

Biotransformation and kinetics

Administrative data

Endpoint:

biotransformation and kinetics

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Well documented study which meets basic scientific principles

Data source

Reference

Reference Type:

other company data

Title:

Unnamed

Year:

2010

Materials and methods

Test guideline

Qualifier:

no guideline followed

GLP compliance:

not specified

Type of medium:

other:

Test material

Test material information

Constituent 1

Reference substance name:

Magnesium

EC Number:

231-104-6

EC Name:

Magnesium

Cas Number:

7439-95-4

Molecular formula:

Mg

IUPAC Name:

magnesium

Test material form:

solid: compact

Results and discussion

Any other information on results incl. tables

Magnesium is the eighth most abundant element and constitutes about 2% of the Earth's crust, and it is the third most plentiful element dissolved in seawater.    Although magnesium is found in over 60 minerals, only dolomite, magnesite, brucite, carnallite, and olivine are of commercial importance.   Magnesium and other magnesium compounds are also produced from seawater, well and lake brines and bitterns.  ; Magnesium compounds, primarily magnesium oxide, are used mainly as refractory material in furnace linings for producing iron and steel, nonferrous metals, glass, and cement.   Magnesium oxide and other compounds also are used in agricultural, chemical, and construction industries.   Magnesium metal's principal use is as an alloying addition to aluminum, and these aluminum-magnesium alloys are used mainly for beverage cans.   Magnesium alloys also are used as structural components of automobiles and machinery.    Magnesium also is used to remove sulfur from iron and steel.

(i) Action of oxygen or air

Magnesium does not react with dry air but slowly gets tarnished in most air due to the formation of a thin film of the oxide, MgO. It burns in oxygen or air with a dazzling light.

                    Δ

2Mg + O₂ ——→ 2MgO                 

 

(ii)    Action of CO₂ and SO₂

Because of its great affinity for oxygen magnesium keeps on burning even in CO₂ or SO₂.

                       Δ

2Mg + CO₂ ——→ 2MgO + C               

                Δ

2Mg + SO₂ ——→ 2MgO + S

 

(iii) Action of nitrogen

On heating magnesium combines with nitrogen to form magnesium nitride.

3Mg + N₂ ——→ Mg₃N₂               

Thus when magnesium burns in air both the oxide and the nitride are formed.

(iv)   Action of halogens

Magnesium on heating with halogens readily forms the halides e.g.

                   Δ

Mg + CI₂ ——→ MgCI₂               

 

(v)    Action of water

Magnesium does not decompose water in cold but decomposes boiling water or steam.

Mg + H₂O ( steam) ——→ MgO + H₂             

(vi)   Action of Acids

Dilute acids reacts with magnesium to produce dihydrogen.

 Mg + 2HCI ——→ MgCi₂ + H₂              

  Mg + H₂SO₄ ——→ MgSO₄ + H₂             

      (dil)              

Mg + 2HNO₃ ——→ Mg ( NO₃)₂ + H₂

However with conc. H₂SO₄, SO₂ is produced

Mg + 2H₂SO₄ ——→ MgSo₄  + SO₂ + 2H₂O             

     (conc.)

 

(vii) Reaction with alkyl halide

Magnesium reacts with alkyl halides in dry ether to form covalent compound called Grignard reagent.

               Dry ether

Mg + C₂H₅I ——→C₂H₅MgI              

 

Magnesium occurs as magnesite MgCO₃, dolomite CaMg(CO₃)₂, Epsomite (MgSO₄.7H₂O) and carnalite K₂MgCl₄.6H₂O and langbeinite K₂Mg₂(SO₄)₃ deposits. The chloride and sulphate of magnesium occurs in sea water from which it being extracted on an increasing scale.

 

Extraction

(a)    From magnesite or Dolomite

The ore is first calcined to form the oxide

MgCO₃ → MgO + CO₂

CaCO₃.MgCO₃ → CaO.MgO + 2CO₂

The metal is obtained from the oxide or the mixed oxides as follows:

(i)     From MgO:

The oxide is mixed with carbon and heated in a current of chlorine gas.

MgO + C + Cl₂ → MgCl₂ + CO

The chloride thus obtained is subjected to electrolysis.

(ii)    The mixed oxides [CaO.MgO] obtained from calcination of  Dolomite [CaCO₃.MgCO₃] are redcued by ferrosilicon under     reduced pressure above 1273 K.

2CaO + 2MgO + FeSi → 2Mg + Fe + Ca₂SiO₄

 

(b)    From Carnallite

The ore is dehydrated in a current of hydrogen chloride and the mixture of fused chloride is electrolysed.

 

(c)    From Sea water

Sea water containing magnesium chloride is concentrated under the sun and is treated with calcium hydroxide Ca(OH)₂. Mg(OH)₂ is thus precipitated, filtered and heated to give the oxide.

The oxide so obtained is treated as in (a) (i) above and then electrolysed.

 

Electrolysis of Magnesium Chloride 

MgCl₂ obtained by any of the above methods is fused and mixed with additional mixture of NaCl and CaCl₂ in the temperature range of 973 – 1023 K. The molten mixture is electrolysed. Magnesium is liberated at the cathode and chlorine is evolved at the anode.

Applicant's summary and conclusion

Conclusions:

Although magnesium is found in over 60 minerals, only dolomite, magnesite, brucite, carnallite, talc, and olivine are of commercial importance.
The Mg2+ cation is the second most abundant cation in seawater (occurring at about 12% of the mass of sodium there), which makes seawater and sea-salt an attractive commercial source of Mg. To extract the magnesium, calcium hydroxide is added to seawater to form magnesium hydroxide precipitate.
MgCl2 + Ca(OH)2 → Mg(OH)2 + CaCl2
Magnesium hydroxide (brucite) is insoluble in water so it can be filtered out, and reacted with hydrochloric acid to obtain concentrated magnesium chloride.
Mg(OH)2 + 2 HCl → MgCl2 + 2 H2O
From magnesium chloride, electrolysis produces magnesium.