METALS METALLURGY. 



as well as highly sonorous. The applications of 

 aluminium have not as yet been so extensive as 

 one would expect from its valuable properties. It 

 is employed for small works of art and jewellery, 

 but is less used by itself than in the form of an 

 alloy with copper. This alloy, which is remark- 

 ably like gold in appearance, was discovered by 

 Dr Percy of London, and consists of copper, with 

 from 5 to 10 per cent, of aluminium. It is nearly 

 as hard as iron, with a tensile strength between 

 that of iron and steel. Aluminium-bronze, as this 

 valuable compound is called, is largely used for 

 decorative objects, watch-chains, pencil-cases, and 

 small articles of that nature. A new method of 

 producing aluminium in large quantities, and at 

 one-tenth of its former price, was patented in 1882. 



Tin. 



England was famous for its tin in the days of 

 the ancient Phoenician traders, and not far 

 from half of all the tin produced in the world 

 is obtained in Cornwall still. About the same 

 quantity is procured from the ores of Southern 

 Asia, found in Malacca, Banca, and Billitan. 

 Bolivia and Peru furnish a much less, though still 

 considerable supply ; but the produce of other 

 countries is insignificant. There is but one ore 

 of tin, called tin-stone, cassiterite, or peroxide of 

 tin, found in sufficient quantity for metallurgical 

 purposes, and it contains, when pure, 78-6 per 

 cent, of the metal. 



The tin ore is stamped to powder and repeat- 

 edly washed, its high density enabling it to be 

 thus readily separated from earthy impurities ; 

 but certain metallic minerals usually associated 

 with it, such as copper and arsenical pyrites, 

 galena, and tungsten, which have nearly the 

 same specific gravity as tin ore itself, cannot 

 be separated by washing. These, accordingly, 

 require to be removed by combined roasting 

 and washing processes before the ore can be 

 smelted. In the roasting, which is done in a 

 reverberatory furnace, the sulphur and arsenic 

 are volatilised, oxides of other foreign metals are 

 formed, and the sulphide of copper is converted 

 into sulphate. The second washing removes these 

 oxides mechanically, and dissolves the sulphate of 

 copper. When the arsenic is saved, the flues are 

 connected with condensers in which it is collected, 

 and afterwards resublimed to form the ' white 

 arsenic ' of commerce. 



The tin ore being prepared as above described, 

 it is then smelted at a high temperature in a 

 reverberatory furnace. Rather more than 20 cwt. 

 are introduced at a charge, mixed with one-sixth 

 part of small-coal, and occasionally also with a 

 little slaked lime or fluor-spar, to serve as a flux 

 for the siliceous impurities. In about six or eight 

 hours the tin is reduced, and is run into cast-iron 

 pans, from which it is ladled into ingot-moulds. 

 It is afterwards refined by the process of liquation. \ 



Tin is a white, beautiful metal, slightly inclining j 

 to yellow. It is rather soft, has a high lustre, and | 

 is not easily acted on by the air at ordinary 

 temperatures ; nor is it readily affected by mois- 

 ture. It is so malleable that it can easily be 

 beaten into foil not exceeding i-jnnrth of an inch 

 in thickness ; and at the temperature of boiling 

 water it possesses considerable ductility. Nitric 

 acid attacks it violently, but neither sulphuric nor 



hydrochloric acids act readily upon it. Of all the 

 cheaper metals, tin preserves its cleanness and 

 brightness best It is consequently largely em- 

 ployed for depositing on the surface of other 

 metals, as in coating thin sheet-iron to produce 

 'tin-plate,' in the 'tinning' of iron hollow ware, 

 and various kinds of copper utensils. Lead pipes 

 are sometimes coated internally with tin to pre- 

 serve them from the action of soft water ; and 

 ' Albion metal,' so much used for coffin furniture, 

 is formed of a layer of tin adhering by pressure to 

 a layer of lead. Mirrors are made by coating 

 glass with an amalgam of tin and mercury. With 

 other metals it forms some valuable alloys, as 

 bronze, gun-metal, bell-metal, Britannia metal, 

 pewter, and solder. Purple of Cassius, a com- 

 pound of tin and gold, gives a beautiful crimson 

 colour to glass and porcelain. Metastannic acid 

 (a hydrated oxide of tin) is used in the preparation 

 of enamels, and under the name of putty powder 

 it is in much request for polishing ornamental 

 stones, as well as other substances. Both the 

 chlorides of tin are extensively used by dyers and 

 calico-printers. 



While the total annual quantity of English 

 copper ore has for a considerable number of years 

 been gradually declining, the amount of tin ore 

 mined in Cornwall and Devon has been gradually 

 increasing. The value of metallic tin, too, although 

 fluctuating from year to year, has been, on the 

 whole, rising; and for the first half of the year 

 1872, it had risen to an average of 153, i8s. per 

 ton, the highest price reached during the present 

 century. In the year 1871, the British produce of 

 tin ore (black tin) was 16,898 tons, yielding of 

 metallic (white) tin 11,320 tons, the value of which 

 amounted to ,1,556,557. During the same year, 

 8583 tons of tin, chiefly from the Straits Settle- 

 ments of British India, were imported into the 

 United Kingdom, while 7770 tons were exported. 

 In 1880, 8918 tons of tin were produced in Britain, 

 value ^813,767. One curious fact is, that from 

 60 to 80 tons are annually consumed in Birming- 

 ham in the manufacture of coffin-lace. 



Mercury or Quicksilver. 



Mercury, as well as some of its compounds, was 

 known to the ancients. Native mercury is ob- 

 tained in globules disseminated through its ores, 

 but it is somewhat rare. A few native amalgams 

 also occur, but the great source of the metal 

 commercially is cinnabar or sulphide of mer- 

 cury, a heavy, bright-red substance, identical in 

 composition with the pigment vermilion. It 

 contains 86-2 of mercury, and 13-8 of sulphur, 

 when pure, but it frequently contains admixtures 

 of other minerals, especially such as contain 

 copper, iron, or aluminium. The most important 

 European mines are those of Idria, in Illyria, 

 and. those of Almaden, in Spain ; the former, 

 according to an estimate made a few years ago, 

 yield annually 250, and the latter 1000 tons of 

 mercury. The Idrian mines were discovered in 

 1497, those of Almaden long before the Christian 

 era. Cinnabar is found at several other places in 

 Europe ; in the Ural and Altai Mountains ; largely 

 in China ; as also in Mexico, Chili, and Peru. 

 In recent years it has been extensively mined in 

 California and Idaho. 



Mercury is extracted from cinnabar (sulphide 



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