Patent GB-253908-A (GB)
Title: A process for treating lead-tin alloys derived from waste material from lead smelting works
IPC: C25C1/24
Filed: 1926-06-14
Abstract: 253,908. Speichert, M., (Assignee of vogel, F.). June 17, 1925, [Convention date]. Alloys, obtaining.- Waste material from lead smelting works, containing lead and tin and a proportion of other metals, more particularly copper, antimony and arsenic, is treated as anode in a bath capable of dissolving lead and tin but not the other metals. An alloy of lead and tin is deposited at the cathode. The anode retains its shape if the proportion of antimony is high enough; otherwise a sludge is formed. A suitable electrolyte may be prepared by dissolving lead carbonate in hydrofluosilicic acid or by anodic solution of refined lead free from silver in that acid to a concentration 16‹ BÚ. 15 per cent of free acid is added which mav be increased to 20-2.5 per cent when the percentage of tin in the anode is higher than that of lead. The voltage is 0.7-0.8 but may be higher when the raw material contains a, large quantity of sulphur. The current density mav be from 100 to 300 amps. per sq. metre but is preferably 150 amps. per sq. metre. The electrolyte is maintained at a temperature of 30-40‹ C. The electrolyte may alternatively be an acid solution of perchlorate of lead but this is not recommended for work on a. large scale owing to the presence of perchlorates in the anode residue giving rise to explosions in the subsequent smelting. The electrolytic cells are preferably of tarred larch wood. It is of particular advantage to use anodes containing 60 to 90 per cent of lead and tin and 10 to 40 per cent of insoluble impurities. The cathode is of electrolytic lead. In an example, the percentage composition of the anode alloy is : tin 45, antimony 10, copper 4, arsenic 0.8, lead 40, iron and sulphur 0.2; that of the cathode deposit is tin 63.2, antimony 0.2, lead 36.6; with no arsenic and traces only of copper; that of the anode residue is tin 21.7, antimony 48.2, arsenic 1.1, copper 11. lead 2.2 together with silicic acid and oxides and sulphates of the heavy metals. In another example, the percentage composition of the anode alloy is : tin 31, antimony 15, copper 3.4, arsenic 0.36, lead 50.3; that of the cathode deposit is : tin 24.5, antimony 2.1, lead 73.4, with traces of copper and arsenic; that of the anode residue is : tin 46.3, antimony 31.5, copper 9.3, arsenic 0.8, lead 12.2. The Specification refers to the following alloys obtained in the metallurgical treatment of lead ores, viz., " tin powder " of percentage composition : tin 13.5, arsenic 0.66, antimony 8.34, lead 77.5, " Dross 1 " of percentage composition : tin 11.75, arsenic 8.88, antimony 13.6, lead 65.76, " arsenic dross " of percentage composition : tin 5.38, arsenic 11.71, antimony 5.78, lead 77.35, antimony dross " of percentage composition tin 1.91, arsenic 3.14, antimony 23.39, lead 71.55, " scrap '' of percentage composition : tin 2.69, arsenic 2.95, antimony 11.34, lead 83. The Specification also refers to the following alloys obtained by smelting a mixture of some of the above, selected according to their composition, with ashes and sweepings, viz., crude antimony-lead " of percentage composition : lead 50-80, tin 5-15, antimony 15-30, arsenic about 1, copper 5-10, and " crude tinlead " of percentage composition : lead 20-50, tin 40-60, antimony 5-10, arsenic about 0.5, copper 3-6. By treating all the residues collectively without separation an alloy is obtained of percentage composition : lead 75.03, tin 7.05, antimony 12.49, arsenic 5.47. This may be treated according to the invention.