Liquation:
This method, is employed to remove the impurities with high melting points from metals having relatively low melting points such a stin(Sb;mp=904K), lead(Pb;mp=600K), mercury(Hg; mp = 234 K), and bismuth (Bi; mp = 545K). In this process, the crude metal is heated to form fusible liquid and allowed to flow on a sloping surface.
The impure metal is placed on sloping hearth of a reverberatory furnace and it is heated just above the melting point of the metal in the absence of air, the molten pure metal flows down and the impurities are left behind. The molten metal is collected and solidified.