TIN. 



of charcoal, f.illpclre, and earth, which he put together 

 Into tlie coppel with the fcori*. It is cafy to fee that a de- 

 touatioii would happen from this, and this muft greatly add 

 to the force of the lire, in ading upon die fcoria, while the 

 ferruginous matter well known to be contained in the char- 

 coal mixed itfelf with the tin, and muft greatly accelerate 

 its calcination, divide its parts, and give the lire a new aftioa 

 over it. The confequence of this perfcftly anfwered ex- 

 pedation, and recovered a large quantity of iilver from the 

 fcorii, ill which the tin had before held it firmly imbodied ; 

 repeated experiments proved the truth of this obfervation, 

 and it was found to be eafy by this means at any time to fe- 

 parate filver from tin, or to purify filver without lofs, by 

 means of lead in which tin has accidentally been imbodied. 



The fcoriae in which tin is mixed with lilvcr, are com- 

 pofed of tin half calcined, and run into an opaque vitrified 

 lubftance, which forms a fort of net-work, in which the 

 lilvcr is confined in extremely fmall particles. If this is 

 thrown into aqua fortis, the whole is ditTolved : but then it 

 requires a very ftrong fire to make the tin lofe its metaUic 

 form ; finally, if the whole is finely powdered, and then 

 put into this menftruum, the filver only is taken up or 

 dilTolvcd, the tin remaining untouched at the bottom of the 

 vcffel. 



The fame gentleman found alfo a method of feparating 

 tin from filver, by means of corrofive fublimate of mer- 

 cury. To conceive the manner in which this feparation is 

 effefted, a piece of fine tin need only be call into a folution 

 of fublimate ; in which cafe the acid of the fea-falt is feen 

 to leave the mercury in order to fix upon the tin. 



And, according to the fame principle, if fublimate cor- 

 rofive be added to a mixture of tin and filver, the fame 

 efFeft is produced, the acid affixes itfelf to the tin, and 

 makes with it a butyrum joviale or butter of tin, the mer- 

 cury becomes diffipatcd in the mean time by the aiftion of 

 the fire, and the filver remains pure and alone ; but in this 

 experiment, if too much corrofive fublimate be added, tliere 

 is danger of lofing fome of the filver ; Cnce the abundant 

 acid will prey upon and carry off a part of that metal, 

 making a fort of luna cornea which difiipates itfelf in the 

 air, or it the operation be performed in a clofe veffel, a 

 butyrum lunarc. 



Gold may alfo be purified from tin in this manner, and in 

 this there is no rilk of lofs, fince the acid which takes up 

 the tin has not the leaft power over that metal : in all thefe 

 procefles, however, the operator muft avoid the fumes iffu- 

 ing from the crucible, for they are very dangerous. 



Thefe methods of feparating of tin from filver are very 

 certain and infaUible, but they are too expenfive to be em- 

 ployed in common, and in larger works. 



The feparating of tin from lead to be employed in the 

 refining of filver is a matter of great importance ; and this 

 may be done in the following manner : melt the lead, and 

 when in fufion thrown into it a quantity of filings of iron, 

 then increafe the fire to a confidcrable degree, and the fur- 

 face of the metal will be covered with a fort of fcum, which 

 is no other than the iron and tin. At this time there (hould 

 be a little alkali fait thrown in, and by this means the fcorias 

 readily feparate themfelves, and the pure lead remains in 

 form of a regulus at the bottom. The fame method may 

 be ufed to feparate tin from filver in the larger way, but it 

 wUl be neceffary for this purpofe to add fome lead,' fince 

 other\vife the fufion will be very flow and difficult, and the 

 tin will calcine without feparating from the filver. This is 

 a very eafy and very cheap method, and wiU obviate moft of 

 the rmfchiefs which happen to the refiners, of which they 

 would have much lefs frequent rcafon to complain, if they 



nicely examined the lead they were to employ. But if gold 

 or filver be mixed with tin, the ftiorteft method in fmall- 

 quantities is to calcine the whole very briikly, and in order 

 to complete the vitrification and feparation of the tin, to 

 caft in a little glafs of lead, wliich will immediately jgin itfelf 

 with it and carry it off^ from the mafs. 



It may feem fingular that iron being one of the hardeft 

 of the metals to melt, and tin being of all the eafieft, they 

 fhould fo readily and eafily unite in thefe experiments ; but 

 this feems to be the refult of one of thofe natural and unex- 

 pefted alliances which accident frequently difcovers to us in 

 bodies. There is one conjefture, however, that may be 

 worthy a place in this refearch, which is, that all tin-ore 

 contains a quantity of arfenic ; and it is well known that iron 

 very readily mixes with arfenic, and is employed to feparate 

 the arfenic from other ores, and a regulus may be formed of 

 arfenic and iron. It is eafy to fuppofe that tin is, in its me- 

 talline form, not wholly divefted of the arfenic it contained 

 when in the ore ; and if this be allowed, it is no wonder that 

 the two metals are eafily brought together by the mediation 

 of that principle. Memoirs Acad. Scienc. Par. 1737. 



Mr. Cramer gives the praftical rules of feparatina filver 

 from tin, thus : Divide one centnerof tin into two equal parts ; 

 put each of thefe into a feparate teft, and add to each fixtee^ 

 centners of granulated lead, and one of copper ; put the 

 whole under the muffle, and make a very ftrong fire ; the 

 tin will be calcined immediately, and will fwim upon the lead. 

 Then diminifh the fire a little, till the afhes of the tin that 

 fwim upon the furface do no longer fparkle : when you fee 

 this, add with- a ladle two centners of glafs of lead to each 

 teft, in fuch a manner that it may be fpread wide over the 

 whole furface of the rejefted calx ; the calx will then change 

 its form of povsrder into that of glafs ; then increafe the fire 

 to its higheft degree, ftir up the whole with an iron rod made 

 warm ; and when thefcorification is perfected, pour out the 

 glafs into a mould ; the fcoris being feparated, put both- 

 the regulufes into two coppels well heated ; and into a tliird' • 

 put fixteen centners of lead, and one of the fame copper 

 ufed in the procefs : examine all thefe beads after the cop- 

 pelling is over ; if the two firft weigh exaftly alike, it is a 

 proof the procefs has been well performed ; and fubtvaftiiig. 

 the weight of the bead, feparated from the third pan, from 

 the joint weight of the other two, the remainder is the 

 weight of the pure filver contained in the quantity of tin 

 which was examined. Cramer's Art of Aflaying, p. 228. 



Tin is found in Europe, Afia, and America, but has not 

 hitherto been difcovered in the continent of Africa. This 

 metal is much lefs generally difTeminated than gold, filver, 

 iron, copper, or lead ; but where it occurs, it is moft fre- 

 quently in large quantities. In Afia it is found on the coarc 

 of Sumatra, and in Siam and Pegu. It is principally im- 

 ported into our Indian pofleffions from Queda, JunkfeiJo.i, 

 Tavai in Lower Siam, and the ifland of Banca. The tin- 

 mines of Banca are faid to be of great extent ; and Mr. Ell- 

 more informs us, that no lefs than from forty to fixty thou- 

 fand peculs of tin are furnifhed by thefe mines annually. 

 Tin is faid alfo to be found at a place five days' journey from 

 Nankin in China. The Indian tin was known to the ancients. 

 Diodorus Siculus mentions it among the produftions of 

 India. . Tin-ftone is found in Mexico in the ftate of ftream- 

 tin, and is procured from alluvial depofitions by waffling. 

 It is alfo faid to occur in Chili, 



Tin-ore occurs in Saxony and Bohemia in beds, and dif- 

 feminated in granite rocks ; it is found alfo in veins in rocks 

 of granite, gneifs, and mica-fiate. Alluvial depofitions of 

 tin are alfo met with in thefe diftrifts. The mines fometimes 

 confift of a mafs of ore formed by the junftion of a multitude 



of 



