cupel
/ˈkjuːpəl/
noun
- A small, shallow, porous container made of bone ash or similar material, used in assaying to separate precious metals from base metals by heating.
- The jeweler placed the gold sample in a cupel to remove impurities.
- In the lab, the cupel was heated until the lead oxidized and was absorbed.
- He carefully handled the cupel, knowing it was essential for the assay.