Dating scan stoke trent

21 Apr

Of the seven metals known in antiquity, only gold occurred regularly in native form in the natural environment.

The others – copper, lead, silver, tin, iron and mercury – occur primarily as minerals, though copper is occasionally found in its native state in commercially significant quantities.

Examples: Flux and slag can provide a secondary service after the reduction step is complete: they provide a molten cover on the purified metal, preventing contact with oxygen while still hot enough to readily oxidize.

This prevents impurities from forming in the metal.

These minerals are primarily carbonates, sulfides, or oxides of the metal, mixed with other components such as silica and alumina.

Roasting the carbonate and sulfide minerals in air converts them to oxides. Carbon monoxide was (and is) the reducing agent of choice for smelting.

Smelting therefore consists of using suitable reducing substances that combine with those oxidizing elements to free the metal.

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A few practical examples: Reduction is the final, high-temperature step in smelting, in which the oxide becomes the elemental metal.A reducing environment (often provided by carbon monoxide, made by incomplete combustion in an air-starved furnace) pulls the final oxygen atoms from the raw metal.The required temperature varies over a very large range, both in absolute terms and in terms of the melting point of the base metal.Most ores are a chemical compound of the metal and other elements, such as oxygen (as an oxide), sulfur (as a sulfide), or carbon and oxygen together (as a carbonate).To extract the metal, workers must make these compounds undergo a chemical reaction.