COP PER this double object in one operation was so great that in sulphur, iron, and silica, successfully without any fuel, when subsequent experiments the aim was merely to concentrate once the initial charge had been fused with coke. The the matte to metallic copper in converters of the Bessemer furnaces used were of ordinary design and built of brick. type. The concentration was effected without any em- Lump ore alone was fed, and the resulting matte showed barrassment till metallic copper commenced to separate a concentration of only 3 into 1. When, however, a hot and chill in the bottom tuyeres. To meet this obstacle blast is used on highly sulphuretted copper ores, a conM. Manhes proposed elevated side tuyeres, which could be centration of 8 of ore into 1 of matte is obtained, with a conkept clear by punching through gates in a wind box. His sumption of less than one-third the fuel which would be coninvention was adopted by the Yivians, at the Aiguelles sumed in smelting the charge had the ore been previously works in France, and at Leghorn in Italy. But the calcined. A great impetus to pyritic smelting was given greatest expansion of this method has been in the United by the investigations of Mr W. L. Austin, of Denver, States, where now more than 400,000,000 ft) of copper Colorado, and both at Leadville and Silverton raw ores, are annually made in Bessemer converters. Vessels of are successfully smelted with as low a fuel consumption as ’several designs are used—some modelled exactly after 3 of coke to 100 of charge. But the largest establishment steel converters, others barrel-shaped, but all with side in which advantage is taken of the self-contained fuel is at tuyeres elevated about 10 inches above the level of the the smelting works of the Mt. Lyell Company, Tasmania. bottom lining. Practice, however, in treating copper There the blast is raised from 600° to 700° F. in stoves, matte differs essentially from the treatment of pig iron, heated by extraneous fuel, and the raw ore smelted with inasmuch as from 20 to 30 per cent, of iron must be only 3 per cent, of coke. The ore is a compact iron eliminated as slag and an equivalent quantity of silica pyrites containing, of copper 2’5 per cent., of silver 3’83. must be supplied. The only practical mode of doing this, oz., of gold 0T39 oz. It is smelted raw with hot blast in as yet devised, is by lining the converter with a silicious cupola furnaces, the largest being 210 in. by 40 in. The mixture. This is so rapidly consumed that the converters resulting matte runs 25 per cent. This is reconcentrated must be cooled and partially re-lined after 3 to 6 charges, raw in hot-blast cupolas to 55 per cent., and blown dependent on the iron contents of the matte. When directly into copper in converters. Thus these ores, as available, a silicious rock containing copper or the heavily charged with sulphur as those of the Rio Tinto,, precious metals is of course preferred to barren lining. are speedily reduced by three operations and without The material for lining, aird the frequent replacement roasting, with a saving of 97’6 per cent, of the copper,, thereof, constitute the principal expense of the method. 93’2 per cent, of the silver, and 93’6 per cent, of the gold. The Nicholls and James process. — Messrs Nicholls The other items of cost are labour, the quantity of which depends on the mechanical appliances provided for hand- and James have applied, very ingeniously, well-known ling the converter shells and inserting the lining; and the reactions to the refining of copper, raised to the gradeblast, which in barrel-shaped converters is low and in of white metal. This process is practised by the Cape vertical converters is high, and which varies therefore Copper and Elliot Metal Company. A portion of the from 3 to 15 ft) to the square inch. The quantity of air white metal is calcined to such a degree of oxidation consumed in a converter which will blow up about 35 tons that when fused with the unroasted portion, the reaction of matte per day is about 3000 cubic feet per minute. between the oxygen in the roasted matte and the sulphurThe operation of raising a charge of 50 per cent, matte in the raw material liberates the metallic copper. The to copper usually consists of two blows. The first blow metal is so pure that it can be refined by a continuous occupies about 25 minutes, and oxidizes all but a small operation in the same furnace. Electrolytic refining and separation of gold and silver. quantity of the iron and some of the sulphur, raising the product to white metal. The slag is then poured and —The principles have long been known on which is based skimmed, the blast turned on and converter re-tilted. the electrolytic separation of copper from the certain During the second blow the sulphur is rapidly oxidized, elements which generally accompany it, whether these, and the charge reduced to metal of 99 per cent, in from like silver and gold, are valuable, or, like arsenic, antimony, 30 to 40 minutes. Little or no slag results from the bismuth, silenium, and tellurum, are merely impurities.. second blow. That from the first blow contains between But it was not until the dynamo was improved as a, 1 per cent, and 2 per cent, of copper, and is usually poured machine for generating large quantities of electricity at a from ladles operated by an electric crane into a reverbera- very low cost that the electrolysis of copper could be tory, or into the settling well of the cupola. The matte practised on a commercial scale. To-day, by reason of also, in all economically planned works, is conveyed, still other uses to which electricity is applied, electrically molten, by electric cranes from the furnace to the con- deposited copper of high conductivity is in ever-increasing verters. When lead or zinc is not present in notable demand, and commands a higher price than copper refined quantity, the loss of the precious metals by volatilization by fusion. This increase in value permits of copper with is slight, but more than 5 per cent, of these metals in the not over £2 or $10 worth of the precious metals being matte is prohibitive. Under favourable conditions in the profitably subjected to electrolytic treatment. Thus many larger works of the United States the cost of converting a 50 million ounces of silver and a great deal of gold are per cent, matte to metallic copper is generally understood recovered which formerly were lost. The mining district to be only about to yh of a cent per ft) of refined copper. of Butte, Mont., alone produces annually about 10,000,000 Pyritic smelting.—The heat generated by the oxidation of ounces of silver and 40,000 ounces of gold, all of iron and sulphur has always been used to maintain com- which is recovered by electrolytic separation. The bustion in the kilns or stalls designed for roasting pyrites. methods of electrolytic refining used in Europe and Since Holloway’s and other early experiments, no serious America necessarily differ only in detail. (See Electeoattempts have been made to utilize the heat escaping from Chemistey.) Most of them employ the multiple system, a converting vessel in smelting ore and matte either in the in which the soluble anodes of cast copper and cathodes same apparatus or in a separate furnace. But considerable of thin copper strippings are hung in lead-lined vats. progress has been made in smelting highly sulphuretted A few works have adopted the series system, in which ores by the heat of their own oxidizable constituents. At the anodes are sheets of rolled copper, one side of Tilt Cove, Newfoundland, the Cape Copper Company which is being dissolved while the refined copper is smelted copper ore, with just the proper proportion of being deposited on the reverse from the adjacent sheet.. 236
