During cupellation, osmium and ruthenium are partly volatilised and iridium is partly absorbed by the cupel. |
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Absorption is facilitated by manufacture of the cupel from a porous material such as bone ash. |
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The metal in the cupel melts and will be observed to become smaller as the process proceeds. |
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In a well-ventilated furnace, the lead melted, oxidized and passed into the pores of the cupel, leaving only a bead of precious metals. |
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The cupel with the lead is placed back into the furnace and heated at 1000 degrees or so. |
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A cupel or cupelling hearth in which precious metals are melted for trial and refinement. |
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Very ornamental, this cupel is an interesting mixture between wood and wicker. |
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Once cooled, the bead is removed from the cupel and weighed. |
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On cooling, the prill is carefully extracted from the cupel. |
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On the other hand, the use of cupel keys is extremely economical, which is why fabricants use them in products where they are only used occasionally. |
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