The Collaborative International Dictionary of English v.0.48:

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.]
   [1913 Webster]

   Cupel dust, powder used in purifying metals.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Cupel \Cu*pel"\ (k[-u]*p[e^]l"), v. t. [imp. & p. p. Cupelled
   (-p?ld"); p. pr. & vb. n. Cupelling.]
   To refine by means of a cupel.
   [1913 Webster]

WordNet (r) 3.0 (2006):

cupel
    n 1: a small porous bowl made of bone ash used in assaying to
         separate precious metals from e.g. lead [syn: bone-ash
         cup, cupel, refractory pot]