Chemical elements
  Magnesium
    Isotopes
    Energy
    Preparation
    Physical Properties
      Atomic Weight, History
      Alloys
    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

Alloys of Magnesium






Alloys of magnesium and zinc resist oxidation more than either of the metals separately. Many other magnesium alloys are very chemically reactive. Le Bon found that magnesium acted much more vigorously on water when it was amalgamated with very small quantities of mercury. In 1864 Phipson described a hard, brittle, lavender-coloured alloy containing 85 parts of tin and 15 of magnesium, which decomposed water at ordinary temperatures and took fire if air were admitted during its preparation. This was a forerunner of a series of very chemically active alloys which contain magnesium.

Alloys containing 5.50 per cent, magnesium and 95.50 per cent. lead rapidly absorb oxygen from moist air. The alloy consisting of the compound Mg2Pb is the most reactive: heat is required when the magnesium exceeds 35 per cent. The oxidation crumbles the alloy to a black powder of Mg(OH)2 and Pb2(OH)2. In presence of water the Pb2(OH)2 oxidises to Pb(OH)2. Free hydrogen is liberated when the alloys are boiled with water; digestion with water under pressure at about 150° C. completely oxidises the lead to lead oxide and liberates the theoretical quantity of hydrogen. Mg2Pb is the only known definite compound of magnesium and lead.

The pyrophoric alloys, such as are used in cigarette-lighters, etc., which produce sparks when struck with hardened steel, contain cerium alloyed with other metals - usually iron. These alloys spark easily, because cerium combines energetically with oxygen at a low temperature. A surface film of black cerium suboxide may be an important agent in the process. According to Hirsch, alloys of magnesium with 75.85 per cent, of cerium are highly pyrophoric. The compound CeMg contains approximately 85 per cent, of cerium, and Vogel says that the alloy corresponding with this compound is pyrophoric. He says the same of the alloy corresponding to Ce4Mg, which contains about 96 per cent, of cerium. Since the combination between magnesium and cerium is endothermic, their alloys are very effective in thermal reduction processes.

The industrially important alloys of magnesium and aluminium, known as magnalium, were originally prepared by making molten aluminium the cathode in a fused salt of magnesium. The earlier magnaliums appear to have contained less than 2 per cent, of magnesium. Magnesium compounds, such as carnallite, are now commonly electrolysed below a red heat and aluminium added during the process.

The tensile strength and elastic limit of the alloys show a maximum at about 8 per cent, of magnesium. They increase in hardness and decrease in density with the magnesium content. The alloys containing 10.30 per cent, of magnesium are malleable, have a density between 2.0 and 2.5, are suitable for castings, easily worked without softening, polish well, and do not fracture easily. They polish better and become more brittle with increase in the magnesium content.1 Magnalium does not easily corrode.

The common magnalium, containing 10 per cent, of magnesium, can be soldered3 and plated with gold or nickel.

Since magnalium retains a silvery lustre it is useful for making certain parts of optical instruments, such as mirrors, and is used in parts of various machines and scientific instruments.

The compound Mg4Al3 consists of silver-white, hard, brittle crystals. There is probably a compound MgAl, and there may be Mg3Al2. Mg2Al and MgAl4 are doubtful.

Lithium and magnesium appear to form solid solutions. Sodium, according to Phipson, forms malleable alloys with magnesium that readily decompose water. According to Mathewson sodium will dissolve about 1.6 per cent, of magnesium at 657° C., but the latter separates out in hexagonal crystals as the temperature falls. Magnesium will dissolve about 2 per cent, of sodium.

Potassium appears not to mix with fused magnesium, though Phipson said it formed malleable alloys that decomposed water.

Copper forms Mg2Cu and MgCu2, indicated by the freezing-point curve, that are brittle, crystalline, and coloured like magnesium. Boudouard found an indication of MgCu on the curve, and claimed to have isolated this compound.

Silver. - Alloys of silver and magnesium are harder than their components, brittle, and more easily oxidised or decomposed by water than magnesium itself. Freezing-point and conductivity curves indicate the compounds MgAg and Mg3Ag.

Gold forms alloys with magnesium that are stable in air at ordinary temperatures. They are yellow when the percentage of magnesium is not over 18 and silver-grey when it is.

Mg3Au (m.-pt. 83° C.), Mg2Au (m.-pt. 796° C.), and MgAu (m.-pt. 1160° C.) are indicated on the freezing-point curve. Mg3Au separates from its alloys with magnesium in large regular crystals. The action between gold and molten magnesium is violent.

Calcium alloys with magnesium in all proportions. The alloys with 10 per cent, and over of calcium are brittle. Ca3Mg4, indicated on the freezing-point curve, is silvery, brittle, stable in air, and only slowly acted upon by water.

Zinc. - The compound Mg4Zn has been described, but MgZn2 seems to be the only known compound of zinc with magnesium. It has been isolated by distilling off, in vacuo, the excess of zinc from a mixture of its constituents, and can be distilled in vacuo without change.

Cadmium and magnesium form a single compound, MgCd, which is greyish white, slightly harder than cadmium, oxidised in moist air, and acted upon readily by water. Two forms of MgCd, differing in hardness, are indicated by electrical conductivity experiments. It melts at 427° C. and dissolves in all proportions in either metal. Magnesium and cadmium form a continuous series of solid solutions.

Mercury. - Magnesium does not amalgamate easily, but amalgams have been made by introducing magnesium ribbon into nearly boiling mercury, and by acting on crystalline magnesium sulphate with potassium amalgam. Silvery crystals of an amalgam have been prepared by rubbing small quantities of magnesium at a time into mercury contained in a warm mortar. The product dulled in air. The immediate product is a thick fluid which cools to a hard crystalline mass. One part of magnesium and 18 parts of mercury (practically MgHg2) give the most satisfactory product. These amalgams reduce many organic compounds.

Cambi and Speroni affirm the existence of MgHg2 and suggest that of MgHg.

Magnesium amalgams decompose water.

Thallium alloys with magnesium blacken in air, especially if the air is moist, through oxidation. The melting-point curve indicates the compounds Mg8Tl3, Mg3Tl, and Mg3Tl2.

Tin forms the compound Mg2Sn when it is melted with magnesium in hydrogen at 700°-800° C. The combination develops heat, and the compound is brittle and easily tarnished in air. It crystallises in regular octahedra.

Antimony forms Mg3Sb2 in steel-grey needles that slowly oxidise in air.

Bismuth forms Mg3Bi2, a steel-grey brittle compound that slowly oxidises in moist air.

Nickel and magnesium are quite miscible in the fused state. The freezing-point curve indicates the compounds MgNi2 and Mg2Ni.


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