TIN. 



and its furface coated with a greenifli cruft. From one 

 hundred grains of Boliemiaii tin-ftone, feventy-two grains 

 aud a half of tin wen^ produced. Wood-tin and (tream-tin 

 wfTC treated in a fimilar manner. Brown tin-llone, expofed 

 to a porcelain fire in a clay crucible, formed a clear denfe 

 glafs, givenini-grey in the middle, but of a bright yellow 

 on the fides and top. The interior of the vcdcl was glazed, 

 ot a milk-white, and overlaid with many fmall groups of 

 needle-ihapcd cryftals of a light -brown colour. The inner 

 furface of the lid was lined with fimilar cryftals. 



j^nal^ss o/Tin-Stcne in the humid luay. — To Klaproth we 

 are indebted for the difcovery of a fimple and effcftual mode 

 of analyfing tin-ftone in the humid way. Boil loo grains 

 of this ore, finely pounded, with a folution of 600 grains 

 of cauftic potafli. Evaporate to drynefs, and then ignite 

 tiiC mafs moderately for half an hour. Add boiling water, 

 which dilTolves the principal part of the mafs, and the re- 

 fiduc rauft again be ignited with fix times its weight of 

 cauftic potafs, and diftblved in water, as before. Add 

 this to the laft folution, and faturate the whole with mu- 

 riatic acid, wh.ich will throw down an oxyd of tin. Let 

 this be re-diftblved by an additional quantity of muriatic 

 acid, and precipitated again by carbonate of foda ; when 

 lixiviated, and dried in a gentle heat, it acquires the form of 

 bright -yellowilh tranfparent lumps. This precipitate muft 

 be finely powdered, and once more diftblved in muriatic acid, 

 aflifted by a gentle heat. The infoluble part confifts of 

 filex. Dilute the folution, which is colourlefs, with from two 

 to three parts of water, and introduce a ftick of zinc, round 

 which the tin will coUeft in a metallic ftate in the form of 

 delicate dendritic laminse. Scrape off the tin, wa(h, dry, 

 2iid fufe it under a cover of tallow in a capfule placed on 

 charcoal, A button of fine metallic tin will remain at the 

 bottom, the weight of which, dedufted from that of the ore, 

 indicates the proportion of oxygen. 



Anal^ts of Bell-metal Ore, or Ttn Pyrites. — To two 

 drachms of finely powdered ore, add one ounce of muriatic 

 acid, and half an ounce of nitric acid : this will diftolve the 

 greater portion of the metallic part without heat, but a 

 entle heat muft be applied to diftolve the whole. The 

 ulphur will float on the furface of the folution, and muft be 

 feparated by filtration. To the folution add carbonate of 

 potafs, which produces a greenifti precipitate ; let this be re- 

 diffolved in diluted muriatic acid, and introduce a cylinder of 

 pure tin, the weight of which is to be previoufly afcer- 

 tained. By this means the copper will be feparated in a 

 metallic ftate. The cylinder of tin muft now be carefully 

 weighed, and the quantity which it has loft muft be noted, 

 and a cylinder of zinc muft be introduced into the fore- 

 going fslution : this will feparate all the tin, which muft be 

 melted with tallow and weighed. Deduft the quantity of 

 tin which was loft by the cylinder, and the remainder will be 

 the quantity of tin from the ore, held in the folution. 



The fulphur feparated by the firft filtration muft be ig- 

 nited, and the unconfumed refidue, diftblved in nitro-muriatic 

 acid, muft be added to the folution, in order to obtain the 

 whole of the contents. The undiflblved part will be the 

 filiceous matrix. 



The copper may be brifl<Iy digefted in nitric acid, which 

 will leave behind a minute portion of oxyd of tin, and af- 

 certain the precife quantity of pure copper contained in the 

 ore. 



The method of getting, preparing, &c. the tin in the 

 Cornifli mines, much the beft and moft confidcrable in the 

 world, is given us in the Philofophical Tranfaftions, Abr. 

 vol. ii. p. 569, &c. and more diftindlly and fully in Pryce's 

 Mineralogy. 



Vol, XXXV. 



f: 



The working of the tin-mines i« very hard and difficult, 

 not only by reafon of the great depth which the veins de- 

 fcend to, even as low as fixty fathoms ; but alfo becaufe 

 the rocks, through which pafTages are frequently cut, are 

 extremely hard. Nor is the foft fhaking earth found in the 

 tin-mines much lefs inconvenient to the workmen, both by 

 reafon of the fetid, malignant vapours it exhales, ami of 

 the current of water often met with in them : thcfc dif- 

 advantages often render it imprafticablc for the workmen to 

 hold it above four hours together. 



The cxillcnce of native tin has been always doubted, and 

 till of late abfolutely denied by all mineralogifts, both ancient 

 and modern : however, Mr. Borlafe, in his Natural Hiftory 

 of Cornwall, p. 185, fuggeftcd, that its exiftencc was far 

 from being improbable ; but he afterwards difcovcred three 

 fpecimens of this metal, native or pure, of which he pre- 

 fented an account to the Royal Society. Mr. Mendcs da 

 Cofta made fevcral experiments on one of thefe fpecimens, 

 with a view of proving that it was really tin ; from which 

 he infers, that it is perfeftly duftile and malleable ; and be- 

 ing bent between the teeth, gives the fame crackling noife as 

 tin always does : in an open fire it melts eafily, calcines on 

 the furface, and fmokes ; but forced in a ftronger fire with 

 borax, it detonates with fmall phofphorefcent fparks, which 

 is a property of pure tin ; and it is only corroded to a white 

 calx in fpirit of nitre, and oil of tartar per deliquium being 

 added to the folution, none of it was precipitated ; whence 

 he concludes, that it was pure tin. Philof. Tranf. vol. Ivi. 

 art. 7. 39. Native tin is alfo faid to have been found in 

 Saxony and Malacca. 



The ores of tin may be generally claft^ed into ftioad or 

 fhode, ftream, and bal or mine tin. The ftioad is disjun<ft, 

 and fcattered to fome diftance from its parent lode, and is 

 pebbly or fmoothly angular, of various fizes, from half an 

 ounce to fome pounds weight. See Shoad. 



Stream-tin ore is the fame as ftioad, but fmaller flzed, &c. 

 See Stream-TVb and Streaming. 



Bal or mine tin-ore often rifes very rich ; and inftances 

 frequently occur, in which it has been difcovered in the 

 richeft and pureft ftate imaginable. This kind of rich ore 

 confifts of the blackeft grains or cryftals, and is ufually 

 found at a moderate depth, or within the day-fide of forty 

 fathoms. 



When the tin-ore is raifed, or dug and drawn out of the 

 mine, and laid by the fhaft, it is iJrR /palled, as the procefs 

 is termed, which confifts in breaking it into fmaller frag- 

 ments, and feparating it from the worthlefs parts. When 

 the beft parts are forted, they are divided into heaps by a 

 hand-barrow, containing a fack and a half, or eighteen 

 gallons. Each of thele fhares, called doles, being turned 

 over, equally levelled and mixed, is then divided with a 

 ftiovel into two equal parts ; and after being bruifed hy 

 large fledges to the fize of a hazel-nut, is equally levelled 

 and divided into four parts ; the bruifing and divifions arc 

 repeated at pleafure, till the quantity dcfigned for fampling 

 is well mixed, and made as fine as common fand. To make 

 a rough guefs, or coarfe effay, the famplcr takes a handful 

 of it, and wafhes it on a ftiovel, till the impure parts :.re 

 carried off by the water, and the more folid and heavy par- 

 ticles, that are left behind, are bruifed with a fledge on the 

 ftiovel, till the whole affumes the appearance of mud. Thi.t 

 is again waihed, and by a peculiar motion the metallic p.ir- 

 ticles are collefted together on the fore-part of the ftiovcl. 

 By repeating thefe bruifings, waftiings, and motions, it be- 

 comes clean black tin, fit for the fmelting-furnace. This 

 is called a i'<i«, (probably from the Trench av/int, forrmr/l,) 

 as it is thrown upon the point of the fhovel by the dextrrity 

 4T ■ "f 



