Smelting of tin by the blast furnace

—This mode of reduction employs only wood charcoal, and its object is to obtain tin of the maximum purity to which it can be brought by manufacturing proce es. The better ores of the stream-works, and the finer tin sands, are selected for this operation. The washings being always well performed, the oxide of tin is exempt from every arsenical or sulphureous impurity, and is a ociated with nothing but a little hematite. It is therefore never calcined. The smelting is effected without addition; only, in a few cases, some of the residuary matters of a former operation are added to the ore. About a ton and six-tenths of wood charcoal are burned for one ton of fine smelted tin. The only rule is, to keep the furnace always full of charcoal and ore. The revived tin is received immediately in the first basin; then run off into the second, where it is allowed to settle for some time. The scoriæ that run off into the first basin, are removed as soon as they fix. These scoriæ are divided into two cla es; namely, such as still retain tin oxide, and such as hold none of the metal in that state, but only in granulations. The metallic bath is divided, by repose, into horizontal zones, of different degrees of purity; the more compound and denser matters falling naturally to the bottom of the basin. The tin which forms the superior zones, being judged to be pure enough, is transvased by ladles into the refining basin, previously heated, and under which, if it is of cast-iron, a moderate fire is applied. The tin near the bottom of the receiving basin is always laded out apart, to be again smelted; sometimes, indeed, when the furnace is turning out very impure tin, none of it is transvased into the second basin; but the whole is cast into moulds, to be again treated in the blast furnace. In general they receive no other preparation, but the green wood ebullition, before pa ing into the market. Sometimes, however, the block of metal is heated till it becomes brittle, when it is lifted to a considerable height, and let fall, by which it is broken to pieces, and presents an agglomeration of elongated grains or tears ; whence it is called grain tin . On making a comparative estimate of the expense by the blowing-house proce , and by the reverberatory furnace, it has been found that the former yields about 66 per cent. of tin, in smelting the stream or alluvial ore, whose absolute contents are from 75 to 78 parts of metal in the hundred. One ton of tin consumes a ton and six-tenths of wood charcoal, and suffers a lo of 15 per cent. In working with the reverberatory furnace, it is calculated that ore whose mean contents by an exact analysis are 70 per cent., yields 65 per cent. on the great scale. The average value of tin ore, as sold to the smelter, is 50 pounds sterling per ton; but it fluctuates, of course, with the market prices. In 1824, the ore of inferior quality cost 30 l. , while the purest sold for 60 l. One ton of tin, obtained from the reverberatory furnace, cost — | 11⁄2 tons of ore, worth | £ 75 | 0 | 0 | | 13⁄4 tons of coals, at 10 s. per ton | 0 | 17 | 6 | | Wages of labour, interest on capital, . | 3 | 0 | 0 | | 78 | 17 | 6 | On comparing these results with the former, we perceive that in a blowing-house the lo of tin is 15 per cent., whereas it is only 5 in the reverberatory furnace. The expense in fuel is likewise much le relatively in the latter proce ; for only 1 3 ⁄ 4 tons of coals are consumed for one ton of tin; while a ton and six-tenths of wood charcoal are burned to obtain the same quantity of tin in the blowing-house; and it is admitted that one ton of wood charcoal is equivalent to two tons of coal, in calorific effect. Hence every thing conspires to turn the balance in favour of the reverberatory plan. The operation is also, in this way, much simpler, and may be carried on by itself. The scoriæ, besides, from the reverberatory hearth, contain le tin than those derived from the same ores treated with charcoal by the blast, as is done at Altenberg. It must be remembered, however, that the grain tin procured by the charcoal proce is reckoned to be finer, and fetches a higher price; a superiority partly due to the purity of the ore reduced, and partly to the purity of the fuel. To test the quality of tin, di olve a certain weight of it with heat in muriatic acid; should it contain arsenic, brown-black flocks will be separated during the solution, and arseniuretted hydrogen gas will be disengaged, which, on being burned at a jet, will deposit the usual gray film of metallic arsenic upon a white saucer held a little way above the flame. Other metals present in the tin, are to be sought for, by treating the above solution with nitric acid of spec. grav. 1·16, first in the cold, and at last with heat and a small exce of acid. When the action is over, the supernatant liquid is to be decanted off the peroxidized tin, which is to be washed with very dilute nitric acid, and both liquors are to be evaporated to di ipate the acid exce . If, on the addition of water to the concentrated liquor, a white powder falls, it is a proof that the tin contains bismuth; if on adding sulphate of ammonia, a white precipitate appears, the tin contains lead; water of ammonia added to supersaturation, will occasion reddish-brown flocks, if iron is present; and on evaporating the supernatant liquid to dryne , the copper will be obtained. The uses of tin are very numerous. Combined with copper, in different proportions, it forms bronze, and a series of other useful alloys; for an account of which see Copper . With iron, it forms tin-plate; with lead, it constitutes pewter, and solder of various kinds (see Lead ). Tin-foil coated with quicksilver makes the reflecting surface of gla mirrors. (See Gla .) Nitrate of tin affords the basis of the scarlet dye on wool, and of many bright colours to the calico-printer and the cotton-dyer. (See Scarlet and Tin Mordants .) A compound of tin with gold, gives the fine crimson and purple colours to stained gla and artificial gems. (See Purple of Ca ius .) Enamel is made by fusing oxide of tin with the materials of flint gla . This oxide is also an ingredient in the white and yellow glazes of pottery-ware. An Account of Tin coined in Cornwall and Devon, from 1817 to 1829 inclusive :— | Years. | Blocks. | Tons. | | 1817 | 25,379 | 4,120 | | | 1818 | 23,048 | 3,745 | 1⁄3 | | 1819 | 18,881 | 3,065 | | | 1820 | 17,084 | 2,773 | 1⁄2 | | 1821 | 19,273 | 3,128 | | | 1822 | 18,732 | 3,137 | | | 1823 | 24,077 | 4,031 | | | 1824 | 28,602 | 4,819 | | | 1825 | 24,902 | 4,170 | | | 1826 | 26,299 | 4,406 | | | 1827 | 31,744 | 5,316 | | | 1828 | 28,179 | 4,696 | | | 1829 | 26,344 | 4,396 | | | Tin imported. Duty, 50 s. per cwt. | Tin exported. | | Cwts. | Cwts. | | 1827 | 2,217 | 2,938 | | 1828 | 3,386 | 3,258 | | 1829 | 2,674 | 2,581 | | 1830 | 15,539 | 10,426 | | 1831 | 8,099 | 12,226 | | 1832 | 29,203 | 21,720 | | 1833 | 35,124 | 39,850 | | 1834 | 46,769 | 46,685 | | 1835 | 17,705 | 23,796 | | 1836 | 23,236 | 17,231 | The principal importations are from the East India Company’s territories and Ceylon:—they amounted in 1832 to 24,585 cwts.; in 1833 to 27,928; in 1834 to 33,611; in 1835 to 10,104; and in 1836 to 17,729. From Sumatra and Java 1961 cwts. were imported in 1832, and 1145 in 1834, but in the other years greatly le . | Declared value of tin and pewter wares and tin-plates exported in | | - | 1827. | 1829. | 1831. | 1833. | 1835. | | 302,255 l. | 235,178 l. | 239,143 l. | 282,176 l. | 381,076 l. | | 1828. | 1830. | 1832. | 1834. | 1836. | | 266,651 l. | 249,657 l. | 243,259 l. | 337,056 l. | 387,951 l. | Of these goods, from two-fifths to three-fifths go to the United States of America. Abstract of Tin coined in Cornwall and Devon, in the year ending June 30, 1835; from the Mining Review , vol. iii. | Smelters. | Blocks of Grain Tin. | Blocks of Common Tin. | Totals. | | 1834. | 1835. | 1834. | 1835. | 1834. | 1835. | | Daubuz and Co. | 728 | 875 | 6114 | 4494 | 6842 | 5369 | | Grenfell and Boase | 344 | 196 | 3776 | 3097 | 4120 | 3293 | | Bolitho and Sons | 229 | 153 | 3829 | 3099 | 4058 | 3252 | | R. and J. Michell | 101 | 75 | 709 | 575 | 810 | 650 | | Wheal Vor Adventurers | — | — | 3925 | 4069 | 3925 | 4069 | | Taylor, Sons and Co. | — | 112 | — | 1250 | — | 1362 | | John Batten and Son | 28 | 49 | 2352 | 2351 | 2380 | 2400 | | Joseph Carne | — | — | 896 | 851 | 896 | 851 | | William Cornish | — | — | 622 | 574 | 622 | 574 | | Gill and Co. | (at Morwelham) | — | — | 758 | — | 758 | — | | Ditto | (at Cal stock) | 60 | — | 605 | — | 665 | — | | Rundle, Paul and Co. | — | 12 | — | 1545 | — | 1557 | | Total | 1490 | 1472 | 23586 | 21905 | 25076 | 23377 | | Total, in 1834, 4180 tons; in 1835, 3899 tons. (6 blocks = 1 ton.) |