Chemical elements
  Magnesium
    Isotopes
    Energy
    Preparation
    Physical Properties
    Chemical Properties
    PDB 101d-1atr
    PDB 1ats-1bup
    PDB 1bvw-1cp8
    PDB 1cqi-1d9d
    PDB 1d9z-1dxe
    PDB 1dxf-1ed9
    PDB 1edr-1f2u
    PDB 1f3f-1fmw
    PDB 1fnm-1g8n
    PDB 1g8t-1gtv
    PDB 1gua-1hnz
    PDB 1hpm-1i95
    PDB 1i96-1iv2
    PDB 1iv3-1jgy
    PDB 1jgz-1k01
    PDB 1k02-1kil
    PDB 1kiz-1l3p
    PDB 1l3r-1lvh
    PDB 1lvk-1mn9
    PDB 1mnd-1n33
    PDB 1n52-1ngg
    PDB 1ngj-1ntb
    PDB 1nu4-1o93
    PDB 1o9t-1ouo
    PDB 1ouq-1pg4
    PDB 1php-1q54
    PDB 1q5h-1qgx
    PDB 1qh1-1r4a
    PDB 1r4x-1rqy
    PDB 1rrf-1s9j
    PDB 1sa0-1svm
    PDB 1svs-1te6
    PDB 1tez-1u0c
    PDB 1u0h-1uhx
    PDB 1uik-1vc9
    PDB 1vcl-1vsd
    PDB 1vst-1wax
    PDB 1wb1-1wzn
    PDB 1x06-1xg4
    PDB 1xhf-1xqa
    PDB 1xr1-1y84
    PDB 1y8a-1yns
    PDB 1yq2-1z0a
    PDB 1z0d-1zc4
    PDB 1zca-1zvq
    PDB 1zvw-2a5l
    PDB 2a5y-2anr
    PDB 2anv-2b8q
    PDB 2b8r-2bku
    PDB 2bm0-2c18
    PDB 2c19-2cic
    PDB 2cie-2d0q
    PDB 2d1k-2dw6
    PDB 2dw7-2egh
    PDB 2eh3-2f6t
    PDB 2f6v-2fmh
    PDB 2fmk-2g3h
    PDB 2g3s-2gl5
    PDB 2gl6-2h7v
    PDB 2h7x-2hne
    PDB 2hny-2i34
    PDB 2i3d-2io7
    PDB 2io8-2j3e
    PDB 2j3q-2jg1
    PDB 2jg2-2nvu
    PDB 2nvx-2oem
    PDB 2ofw-2our
    PDB 2ous-2pcl
    PDB 2pda-2px3
    PDB 2pxi-2q5z
    PDB 2q66-2qlx
    PDB 2qm1-2qwy
    PDB 2qx0-2rdr
    PDB 2rds-2uxq
    PDB 2uxr-2vbn
    PDB 2vbu-2vk8
    PDB 2vkf-2w7x
    PDB 2w83-2wi3
    PDB 2wia-2wzd
    PDB 2wzg-2xcp
    PDB 2xdg-2y0s
    PDB 2y3p-2z4r
    PDB 2z4s-2zjy
    PDB 2zkj-301d
    PDB 302d-3a5k
    PDB 3a5l-3ak8
    PDB 3ak9-3bb3
    PDB 3bb4-3bsu
    PDB 3btx-3c95
    PDB 3c9h-3ckg
    PDB 3clc-3cxc
    PDB 3cxo-3der
    PDB 3des-3du3
    PDB 3du7-3e84
    PDB 3e8m-3eni
    PDB 3eno-3ezw
    PDB 3ezx-3fcs
    PDB 3fct-3fqr
    PDB 3fqt-3g3y
    PDB 3g45-3gj3
    PDB 3gj4-3gve
    PDB 3gvn-3hdz
    PDB 3hfw-3hrz
    PDB 3hs0-3hzt
    PDB 3hzv-3iaf
    PDB 3iak-3ilo
    PDB 3imd-3jvt
    PDB 3jvv-3ka6
    PDB 3ka8-3kkp
    PDB 3kkq-3kxi
    PDB 3kxo-3ldw
    PDB 3lee-3lwm
    PDB 3lwn-3mey
    PDB 3mf4-3n23
    PDB 3n2a-3nkv
    PDB 3nl3-3ocm
    PDB 3ocu-3oiu
    PDB 3oiv-3oye
    PDB 3oyf-3pu9
    PDB 3pwx-3rmj
    PDB 3ro8-3t3p
    PDB 3t5t-3ukd
    PDB 3umm-3v9w
    PDB 3v9x-412d
    PDB 421p-4aov
    PDB 4ap5-4dg1
    PDB 4dh1-4dug
    PDB 4dwd-4en4
    PDB 4en5-4fk1
    PDB 4fkx-8ici
    PDB 8ruc-9rub

Preparation of Metallic Magnesium






Magnesium was first prepared by acting on its chloride with potassium. Later, a mixture of magnesium chloride, calcium fluoride, sodium chloride, and potassium chloride, or of carnallite and fluorspar, was used - sodium being substituted for potassium.

Proposals have been made to reduce the sulphate with iron or hydrocarbons; to reduce magnesium minerals, such as magnesite or dolomite, with coal and ferric oxide; and to reduce the double cyanide of sodium and magnesium with zinc.

The direct reduction of fused magnesia by carbon is violent at 2030° C., and potassium vapour at a strong red heat will also reduce it.

Magnesium is now prepared by electrolysis. Sir Humphrey Davy obtained an amalgam of magnesium by electrolysing a mixture of magnesia and red mercuric oxide between a platinum anode and a mercury cathode. Subsequent experimenters electrolysed solutions of magnesium salts: Becquerel obtained the metal from a concentrated solution of the chloride, and a solution of the double sulphate of ammonium and magnesium was electrolysed at 70°-100° C.

Electrolytic call for magnesium
Gratzel electrolytic call for magnesium
An attempt was made to electrolyse molten double sulphides of magnesium and the alkalies. In 1852 Bunsen electrolysed the molten anhydrous chloride; Matthiessen mixed three equivalents of potassium chloride with every four of magnesium chloride, and Fischer took the natural step of employing carnallite - the naturally occurring double chloride of magnesium and potassium. Magnesium is now chiefly manufactured by electrolysing this fused salt. Carnallite is less volatile than magnesium chloride, and more easily dehydrated without formation of magnesia.

The electrolysis is performed in an iron pot which acts as cathode. The anode is of carbon, and holes in the porcelain pot surrounding it permit communication between the anodic and cathodic compartments. To maintain the molten condition of the liberated magnesium the cell is placed in a furnace. A number of such cells is usually connected in series with a source of current, so that the P.D. between each pair of electrodes is about 8 volts. A usual current density is about 1000 amp. per sq. metre. The chlorine is carried off by a side pipe, and the molten magnesium collects in the cathodic compartment on the surface of the molten electrolyte. It is protected from oxidation by an atmosphere of inert gas. The holes between the anodic and cathodic compartments are arranged to avoid any passage of the upper layer of magnesium into the anode compartment. The working temperature is apparently between 700° C. and 800° C.

The globules of magnesium do not coalesce in the presence of magnesium oxide or magnesium sulphate. The addition of ammonium chloride during the fusion of the magnesium chloride prevents the formation of oxide. Any sulphate is decomposed by adding enough carbon to the fused chlorides: the oxide thus produced is converted into chloride by ammonium chloride. Oettel found that the addition of calcium fluoride removed the disinclination of the magnesium globules to coalesce.

Swan could say in 1901 that the only company known to be manufacturing metallic magnesium was the Aluminium und Magnesium Gesellschaft, Hemelingen. Their electrolyte contained equimoleeular proportions of magnesium, potassium, and sodium chlorides. It was prepared from carnallite by adding sodium chloride. Anhydrous magnesium chloride was continuously added during the process (which was continuous) to keep the bath composition constant. The electrolyte was kept basic and contained calcium fluoride.

Molinari says that, prior to the Great European War, the world's consumption of metallic magnesium approached 100 tons. American companies are now producing considerable quantities.

Magnesium can be purified by distillation, but it is more usually purified by remelting with pure carnallite in an iron crucible. The floating metal is ladled off and poured into ingots. It is usually converted into wire by squeezing the semifluid metal through dies, and is then commonly rolled into ribbon. It is also handled commercially as powder.

Magnesium metal may contain from 6-17.5 c.c. of occluded hydrogen, and from 1.2-4.1 c.c. of occluded carbon monoxide, in every 20 grm. From 0.05-0.07 per cent, of silica, and about 0.08 per cent, of iron and aluminium, have been found in it. Samples containing small amounts of alumina and ferric oxide have been found to be free from carbon, alkali metals, and alkaline earth metals.


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