Question

Describe the process of cupellation process.

Answer 1

1. Cupellation is a refining process used to purify silver by removing lead impurities.
2. Impure silver containing lead is placed in a bone-ash crucible called a cupel.
3. The cupel is heated in a reverberatory furnace.
4. A blast of air is passed over the molten metal.
5. Lead impurities oxidize to lead oxide (PbO) due to exposure to air.
6. Lead oxide is absorbed by the porous cupel or blown away by the air current.
7. The pure silver remains behind in the cupel as a shiny metal.
8. This process is possible because lead oxidizes more readily than silver.
9. Cupellation is commonly used after extracting silver from argentiferous lead using processes like Parkes process.