A process in assaying for freeing gold, silver, and pla-tina, from alloys of other metals. It is performed as follows: - the precious metal is put together with a due proportion of lead into a cupel, and the fusion is effected by exposing them to a considerable heat in a muffle or small earthen oven fixed in the midst of a furnace. The lead continually vitrifies or becomes converted into a glassy calx, which dissolves all the imperfect metals. This fluid glass, with all its contents, soaks into the cupel, and leaves the precious metal in a state of purity. During the cupellation, the scoriae running down on all sides of the metallic mass produce an appearance called circulation, by which the operator judges whether the process is going on well. When the metal is nearly pure, certain prismatic colours flash suddenly across the surface of the globule, which soon afterwards appears very brilliant and clean; this is called brightening, and shows that the operation is ended. After gold has passed the cupel, it may still contain either of the other perfect metals, platina and silver.

The former is seldom suspected; the latter is separated by the operation called quartation and parting.