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Cupel-la′tion.

An alloy of silver and lead is exposed to a red heat on the floor of a muffle, where a current of air plays over its surface. The lead is converted into the protoxide, melts, and runs off, leaving the refined silver.

In assaying silver it is purified in a small cupel subjected to an oxydizing heated blast. This leaves it pure silver, the lead passing into the porous vessel.

The assay of gold is more complex. The copper and other oxydizable metals are removed by cupellation with lead. A large excess of silver is then added to the alloy, which is rolled into a sheet called a cornet. The silver is dissolved out with nitric acid, which leaves the gold as a sponge. This is called parting.

The process of refining silver with lead in a furnace is described by Ezekiel, and is regarded by Napier as substantially coincident with the modern cupellation.

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