The color of a metal depends on its selective absorption of light waves of different wave lengths. Unless the light penetrates the metal, it is all reflected and the metal looks white. The selection of light rays may be from several parts of the spectrum; this is the case with copper which has a reddish hue. Anything which increases the absorption deepens the color. This can be done by reflecting a ray of light many times from two or more surfaces made of a given metal. Silversmiths and gold smiths accomplish the same result by finely grooving a metal surface. Owing to this ab sorption of light by a metal the color of the light reflected differs from that transmitted. Thus gold can be made so thin that some light will get through. This light is bluish green, while in reflected light, gold appears yellow. Silver is white by reflected light, while the transmitted light through silver foil is blue.
Malleability is the property that permits a metal to be hammered or rolled into sheets. Ductility that which permits it to be drawn into wire. Both are dependent on the tenacity of the metal, the latter more than the former. The relative malleability and ductility of the principal metals is as follows: Certain physical constants of some of the metals are shown in the following table: The mobility of the molecules of a metal is increased by temperature. Thus a coiled nickel
wire may be made absolutely straight by sus pending a weight from one end and heating the wire to white heat by the flame from an alcohol lamp or Bunsen burner. Zinc at its melting point is brittle, but at a temperature of 150° is quite malleable.
Metals can occlude gases. Thus a given vol ume of palladium cooled from red heat in hy drogen absorbs 900 times its volume of that gas. Hydrogen passes through red hot iron or platinum, and nascent hydrogen, assisted by atmospheric pressure will pass through a thin plate of cold iron as shown by Devine A liquid metal can penetrate a solid; a bar of on rubbed with mercury absorbs enough in a very short time to become brittle. A solid meu may penetrate another when both are colt This can be shown with plates of gold and lesi rolled together and allowed to stand.
For further information about the differem metals, see special article under the title cf each; as ALUMINUM ; ANTIMONY ; IRON ; LEO.
Smut, etc. Consult Friend, J. N. (editor:. (Textbook of Inorganic Chemistry) (9 vols. London 1914-17).