GB347222A - A new or improved process of refining metals and alloys of low melting points - Google Patents

Abstract

In the purification or separation of metals of low melting-points by heating the metal under treatment to a temperature sufficient to melt the mass but below the melting-point of alloys of the metals present as impurities with each other, the metal is filtered at a temperature at which the main mass is molten. A metal may be added to alloy with the impurities. Lead containing copper, tin and antimony is heated to 327 DEG C. and the solid alloys of copper and tin, copper and antimony are filtered off. Copper or aluminium may be added to the mass if the initial copper content is insufficient to precipitate the antimony as an alloy. Alloys of lead and tin used as bearing metals may be purified in a two-stage process by heating the alloys to a temperature slightly above the melting-point of the main mass, filtering off the solid copper-tin alloy, and then adding aluminium to the filtrate to combine with antimony and copper and filtering off the aluminium-antimony and aluminium-copper alloys. Aluminium or zinc may be added in the first stage to remove copper and further aluminium added in the second stage to remove antimony. The separated copper-tin alloys may be used as bearing metals. The filtering apparatus may comprise a cylinder of iron or other metal unattacked by the molten mass, in which a piston moves with a clearance through which the molten metal may pass. The apparatus may also comprise a series of metal plates, assembled face to face, but spaced slightly apart. This grid of plates is used with the edges towards the molten mass which is forced through the filter so formed. Specification 241,224, [Class 82 (i), Metals, Extracting &c.], is referred to.