TIN. 



G23 



celebrated for its tin mines from the remotest ages ; 

 and it still continues the most productive country 

 in this metal in all Europe. The mountains which 

 separate Galicia from Portugal were also very pro- 

 ductive of tin in ancient times, and still continue 

 unexhausted. The mountains between Saxony and 

 Bohemia have been wrought as tin mines for several 

 centuries, and still continue productive. Mines of 

 it occur in the peninsula of Malacca, in India, in 

 Chile and in Mexico. The tin-stone (or peroxide 

 of tin) is the only ore used for obtaining "metallic 

 tin. The first process to which it is subjected is 

 grinding. The ground ore is then washed, which 

 removes the impurities ; for the specific gravity is 

 so high that it is easy to wash away the earthy 

 matter, and even some of the foreign metallic ores 

 with which it is often mingled. But there are 

 other bodies so nearly of the same specific gravity 

 of the tin ore that they cannot be thus removed. 

 The next process is roasting the ore in a reverbera- 

 tory furnace; this expels the sulphur and arsenic 

 with which the foreign matters were combined, and 

 thus diminishes their specific gravity so much that 

 they can now be washed away. The ore, thus 

 freed as much as possible from foreign matter, is 

 mixed with the requisite fuel and lime-stone, and 

 heated strongly in a reverberatory furnace, so as to 

 bring the whole into the state of fusion, which is 

 kept up for about eight hours. The lime unites 

 with the earthy matters still mixed with the ore, 

 and flows with them into a liquid glass, while the 

 coal reduces the oxide of tin to the metallic state. 

 It falls by its weight to the bottom, and is, at the 

 end of about eight hours, let out by tapping a hole 

 in the furnace, which had been filled with clay. 

 The tin thus obtained is still very impure. It is 

 returned to the furnace, and exposed to a heat just 

 sufficient to melt it. The pure tin flows out into a 

 kettle, while a quantity of impurities remains be- 

 hind. The tin in the kettle is kept in fusion and 

 agitated, by which a quantity of impurity is accumu- 

 lated on its surface. It is skimmed off, and the 

 tin, now refined, is cast into blocks, weighing each 

 about 300 pounds. 



Tin, when pure, has a fine white colour, like 

 silver ; and, when fresh, its brilliancy is great. It 

 1ms a slightly disagreeable taste, and emits a pecu- 

 liar smell when rubbed. Its hardness is between 

 that of gold and lead. Specific gravity, 7'28. It 

 is very malleable ; tin leaf, or tinfoil, as it is called, 

 is about one thousandth part of an inch thick ; and 

 it might be beat out into leaves as thin again, if 

 such were wanted for the purposes of art. Its 

 ductility and tenacity are much inferior to those of 

 most of the metals known in early times. It is 

 very flexible, and produces, while bending, a re- 

 markable crackling noise, sometimes called the cry 

 of tin. It melts at 442 Fahr. When cooled 

 slowly, it may be obtained crystallized in the form 

 of a rhomboidal prism. After a short exposure to 

 the air, it loses its lustre, and assumes a grayish- 

 black colour, but undergoes no further alteration. 

 Neither is it sensibly altered by being kept under 

 wiiter. When tin is melted in an open vessel, its 

 surface becomes very soon covered with a gray 

 powder, which is an oxide of the metal. If the 

 heat be continued, the colour of the powder gradu- 

 ally changes, and at last it becomes yellow. It 

 forms two oxides. The protoxide has a black col- 

 our, but when combined with water, is white. The 

 peroxide is yellow, and, in certain circumstances, is 

 transparent, and nearly white. The black oxide, or 



protoxide, may be obtained by dissolving tin in 

 muriatic acid till a saturated solution is obtained, 

 precipitating the liquid by means of carbonate of 

 soda, and collecting the precipitate on a filter, wash- 

 ing and drying it at a temperature not exceeding 

 180 Fahr. By this process a white powder is ob- 

 tained, which is a hydrated protoxide. It requires 

 to be raised to a red heat in a glass retort to expel 

 the water, after which it is a black powder, devoid 

 of lustre, tasteless, and insoluble in water. When 

 heated in the open air, it takes fire, burns brilliant- 

 ly, and is converted into peroxide. It is distin- 

 guished from the peroxide of tin not only by its 

 colour, but by being insoluble in ammonia and in 

 carbonate of potash. The other oxide exists abun- 

 dantly in nature, though rarely free from admixture 

 with iron. When pure, its colour is yellow. It is 

 translucent, or almost transparent, and crystallizes 

 in octahedra with square bases. Specific gravity 

 6-6. It is insoluble in all acids, until it has beea 

 fused with an alkali. Tin combines with chlorine 

 in two proportions, forming the protochloride of tin, 

 and the perchloride of tin. The former of these 

 may be formed by heating together an amalgam of 

 tin and calomel, or by evaporating to dryness the 

 protomnriate of tin, and fusing the residue in a 

 closed vessel. It has a gray colour, a resinous lus- 

 tre and fracture, and takes fire when heated in chlo- 

 rine gas, and is converted into the perchloride. The 

 perchloride of tin has long been known under the 

 name of fuming liquor of Libavius, because it was 

 discovered by Libavius, a chemist of the sixteenth 

 century. It is usually prepared by mixing together 

 an amalgam of tin and corrosive sublimate, and dis- 

 tilling with a very moderate heat. At first, a col- 

 ourless liquor passes into the receiver, consisting 

 chiefly of water : then the fuming liquid rushes all 

 at once into the receiver in the state of vapour. It 

 is colourless, like water, and very fluid. When 

 three parts of it are mixed with one of water, the 

 mixture condenses into a solid mass. It acts with 

 great violence on oil of turpentine. There are com- 

 pounds, also, of tin with bromine and with iodine. 

 Tin also combines with phosphorus and with sul- 

 phur. One combination of tin and sulphur (the 

 persulphuret) has long been known in chemistry 

 under the name of aurum mosaicum, or mosaic gold. 

 It is formed by mixing twelve parts tin, seven parts 

 sulphur, three parts mercury, and three parts sal- 

 ammoniac, and exposing the mixture to a strong 

 heat, for eight hours, in a black-lead crucible, to 

 the top of which an aludel is luted. The mosaic 

 gold sublimes. It may also be formed by mixing to- 

 gether in a retort equal parts of sulphur and oxide 

 of tin, and distilling. When pure, it is in the form 

 of light scales, which readily adhere to other bodies, 

 and which have the colour of gold. Tin and arsenic 

 may be alloyed by fusion. The alloy is white, 

 harder and more sonorous than tin. Tin and anti- 

 mony may be united together in various proportions. 

 Equal parts of tin and molybdenum melt into a 

 blackish-gray, granular, brittle, soft mass. Tin 

 does not combine readily with iron. An alloy, 

 however, may be formed by fusing them in a close 

 crucible, completely covered from the external air. 

 Tin plate is formed by dipping into melted tin 

 thin plates of iron, thoroughly cleaned by rubbing 

 them with sand, and then steeping them twenty- 

 four hours in water acidulated by bran or sulphuric 

 acid. The tin not only covers the surface of the 

 iron, but penetrates it completely, and gives the 

 whole a white colour. Tin and zinc may be easily 



