The Collaborative International Dictionary
Cupel dust
Cupel \Cu"pel\ (k[=u]"p[e^]l), n. [LL. cupella cup (cf. L. cupella, small cask, dim. of cupa) : cf. F. coupelle. See Cup, and cf. Coblet.] A shallow porous cup, used in refining precious metals, commonly made of bone ashes (phosphate of lime). [Written also coppel.]
Cupel dust, powder used in purifying metals.