Silver is extracted from lead ores using a process called cupellation, often involving large furnaces.
Cupellation: A Detailed Look
Cupellation is a refining process used to separate noble metals, like silver, from base metals, such as lead. Here's a breakdown:
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Ore Preparation: The process begins with crushed ore that contains silver, along with impurities like lead and other base metals.
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Furnace Heating: The crushed ore is heated to high temperatures in a furnace.
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Oxidation of Base Metals: At these high temperatures, the base metals, primarily lead, oxidize. This oxidation forms lead oxide (litharge).
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Absorption by Cupel: The molten lead oxide is then absorbed into a cupel. A cupel is a shallow, porous dish traditionally made of bone ash or magnesia. These materials are chosen for their ability to absorb molten oxides.
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Separation: As the lead and other impurities are absorbed into the cupel, molten silver remains.
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Silver Recovery: The molten silver is then drawn off and further processed to achieve the desired purity.
In modern industrial settings, this process is carried out in large furnaces designed for efficient and controlled separation. The cupel might be replaced by a more robust, engineered material, but the underlying principle of absorbing the base metal oxides remains the same.
