What is a shallow porus cup, used in refining precious metals, commonly made of bone ashes (phosphate of lime). [Written also coppel.] Cupel dust, powder used in purifying metals called?

cupel — A shallow porus cup, used in refining precious metals, commonly made of bone ashes (phosphate of lime). [Written also coppel.] Cupel dust, powder used in purifying metals. (Webster's 1913.)

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