Metal (Gr.Metal 1100214 ), a term including about 50 elementary substances which possess, either wholly or in part, certain well marked physical and chemical properties, of which the most universal and characteristic is lustre. The peculiar brilliancy and reflective power of the metals, which may be enhanced by polishing, results from their great opacity. The color of the metals is generally white with a grayish, bluish, or pinkish tint; copper and gold are the only exceptions. In extremely thin films some of the metals allow the passage of certain rays of light. Gold leaf transmits light of a faint greenish hue. Most of the metals have a high specific gravity, a property which was regarded as characteristic until the discovery of the alkaline metals, which are lighter than water. With the exception of arsenic, they may all be fused, the temperature required for fusion varying from 100° F. to the highest heat of the oxy-hydrogen blowpipe. Some of the metals may be volatilized. Mercury, the only liquid metal, is solidified at - 39° F. Arsenic when heated passes directly into vapor without fusion. Most of the metals possess a certain mobility of particles that allows of their being extended or otherwise altered in form.

The two nearly related properties of malleability and ductility, resulting from this, are not possessed by the metals in the same degree. A few of them, as antimony, arsenic, and bismuth, are decidedly brittle. Some assume a plastic condition before complete fusion, notably iron and platinum; on this property depends the operation of welding. The strength of the metals is very dissimilar, iron in the form of wire being about 26 times as tenacious as lead. They are all conductors of heat and electricity, although differing widely in this respect. The metals at present known, with the name of the discoverer and date of discovery of each, together with their atomic weights, are given in the following table:

METAL.

Atomic weight.

Discoverer.

Date of discovery.

Gold..............

197

Known to the ancients.

....

Silver.............

108

" " "

..

Mercury..........

200

" " "

..

Copper...

63.4

" " "

....

Lead...

207

" " "

....

Tin...............

118

" " "

-----

Iron...

56

" " "

....

Bismuth...

210

Basilius Valentinus.

15th century.

Antimony...

122

" " "

"

METAL.

Atomic weight.

Discoverer.

Date of discovery.

Zinc.......

65

First mentioned by Paracelsus........

16th century.

Arsenic..........

75

Schroder.............

1694

Cobalt......

59

Brandt........

1733

Platinum.......

197.4

Ulloa.............

1736

Nickel...........

59

Cronstedt............

1751

Manganese........

55

Gahn...........

1774

Molybdenum......

96

Hjelm...........

1782

Tungsten (wolf- ram)..........

184

D'Elhujar...........

1783

Titanium....

50

Gregor..

1789

Yttrium..........

616

Gadolin

1794

Chromium.........

52.2

Vauquelin

1797

Tellurium.........

128

Klaproth.

1798

Niobium (colum-bium)...........

94

Hatchett.............

1801

Tantalum........

182

Ekeberg

1802

Palladium.........

106.6

Wollaston..

1803

Osmium.........

199

Tennant.............

1803

Cerium...........

92

Klaproth, Hisinger,

1808

Iridium...........

198

Descotils and Tennant

1803-4

Rhodium.........

104.4

Wollaston...........

1804

Potassium........

39.1

Davy................

1807

Sodium...........

23

"

1807

Barium...........

137

"

1808

Strontium........

87.6

"

1808

Calcium...

40

"

1808

Lithium....

7

"

1818

Cadmium.........

112

Stromeyer............

1818

Zirconium (beryllium)...

89.6

Berzelius...

1824

Aluminum........

27.4

Wohler..............

1827

Glucinum.....

9.4

Wohler and Bussy

1828

Thorium..........

115.7

Berzelius...

1828

Magnesium...

24

Davy...

1828

Vanadium...

51.3

Sefstrom...

1830

Lanthanum.......

93.6

Mosander...

1889

Uranium...

120

Peligot...

1840

Didvmium

95

Mosander.

1841

Erbium...

112.6

"

1843

Ruthenium...

104

Claus...

1846

Rubidium...

85.4

Bunsen and Kirehhoff

1860

Caesium...........

133

" " "

1860

Thallium...

204

Crookes (Lamv)......

1861

Indium...

113.4

Reich and...ichter___

1863

With a few exceptions, the names and dates in the above list refer to the actual production of the metal. In many instances the metallic compounds were known and studied long before the metal itself was isolated. Some of the rarer metals have never been prepared in a pure form. Pelopium, formerly enumerated among the metals, has been shown to have no existence; and the existence of terbium is doubtful. The last four metals were discovered by means of the spectroscope. - The following tables exhibit the mutual relations of some of the more important metals in physical properties: