OXIDATION OF METALS is effect ed either by the air and heat, by burning with nitrate of potash, by water, by acid ulous solution, the excess of acid being subsequently withdrawn by an alkali, or other substance of greater affinity.
Oxidation renders metals susceptible of the action of acids, and hence their va riety of salts. If the metal becomes .a salt, it was previously an oxide, or was oxidized in the process.
To oxidize metals, after they are melt ed they are exposed in the furnace in a flat dish, and stirred. Zinc and mercury vaporize and require one to be exposed to air previously, and the other in a long necked vessel, that it may not wholly escape, and yet rise to contact with air.
After metals are melted and burned they form oxides, 8 of which are white; iron, lead. copper, manganese, and mer cury, which are red, or black, or yellow. Silver, too, is olive, and antimony yellow.
Further heat converts these powders into glass, and they are generally soluble in acids or alkalies. Heated with charcoal, carburet of iron, oil, &c., they may be restored to the metallic form.
Iron combines with 2875 and 48'12 of oxygen in 100, to form its black and red oxide.
Zinc with 24.21.
Arsenic with 34.93 and 52.4.
Manganese with 28.75 and 57.5. Bismuth with 11.28.
Antimony 18.6.
Copper 12.5 for red, and 2.5 for black. Silver 7.272.
Mercury 4 for black, and 8 for red. Lead 11.53 for red, and 15.384 for brown.
The alkaline metals absorb still more : magnesium 66.6, sodium, 83.3, calcium 38.39, potassium 20, and barium 11.42 all white.
Gold affords 2 chemical oxides, and its leaves are changed to purple color by electricity.