B I S 



mfnftrunm from time to time, till all the foluble parts of 

 the ore are taken ..p. Add together the folut.ons and 

 reduce them bv gentle evaporation to about hall their duik. 

 (if auv cryftals ar-- depofited, add a little pure warm water 

 iud fu'fficient to take them up again); tl.tn pour the whole 

 into « large quantity of rain water, at leall twenty times 

 the bur< of the fohu.on. The liquor will immechately al- 

 fumc a milky appearance, and, by (landing a (liort time, 

 «-;H dcpofit a white heavy precipitate (.,), wl.uh, when 

 carefilly lixiviated, i. pure cxy<l of bifmuth. Add all the li- 

 quors together, and concentrate them by evaporation to one 

 half of their bulk ; then drop in a ftrong folution ot mun- 

 ateJ ammonia, as long as any precipitate takes pUre ; de- 

 cani the fupcrnatant fluid as accurately as poflible, aiid, 

 without walhing the precipitate, digcft it for fome tmie with 

 modciately ilrong nitric acid ; the undifFolved part ot the 

 precipitate being feparated, waflied, and dried, is pure mu- 

 rial of/iIvcr (i). The nitrous folution is now to bcdiUited 

 with a large quantity of cold water, and a precipitate of 

 oxyd of bilmi.th (O'will be thrown down. The dihited ni- 

 trous folution being mix<.d with the other liquor, the whole 

 muft be evaporated, till a conliderable number of cryftals are 

 depofited ; at this time, the addition of fulphuric acid will 

 occalion a white depofit ai fulphat of had [d). The re- 

 mainder of the folution is now to be fuperfatuiated with 

 caullic liquid ammonia, by which the iron will be depofited 

 in the (late of brown oxyd (e), and the copper will form 

 with the ammonia a blue folution ; this being faturated 

 Uightly to excefs with fulphuric acid, will depolit the cop- 

 per (/') upon a piece of clean iron. The itlidue of the ore 

 that was undilTolved by nitric acid, being weighed, and ex- 

 pofed to a low red heat, will give out its fulphur {g), the 

 quantity of which may be eftimated with confiderable accu- 

 racy by the lofs of weight. It is now finally to be digelled 

 with ten times its weight of boiling muriatic acid, by which 

 fome oxyd of lead will be taken up ; and this, by evapora- 

 tion and the addition of fulphuiic acid, may be procured in 

 the llate of fulphatcd lead {h). The relidue being wafhed 

 and dried is the llony gangue of the ore (<). 

 Hence the ore will be decompofed into 



Oxyd of bifmuth (a) and (f), 

 Muriated filver (b), 

 Sulpliatcd lead (^/) and (A), 

 Oxyd of iron (c). 

 Metallic copper (j"). 

 Sulphur (jf), 

 Stony matrix (;) 

 ^ 3. ReduQion of Jjifmiilh ores. 

 The fcparation of this metal from the fubflances with 

 which it is found united in the mine, and the rcduclion of 

 it to a marketable llate, is perhaps the eiifu 11 of all the me- 

 tallurgical procefTes, on account of tl:e ready fufibility of 

 bifmuth, and it: being found for the moft part in the me- 

 tallic llaSe. The following were the methods praftifed in 

 the time of Agricola (Uc Re Mctallica, p. 349.) A round 

 pit, two or three feet wide, was lined with well rammed 

 clay and charcoal, and covered with billet wood, upon 

 which were laid alternate llrata of ore and wood. When 

 the pile was thus built to a fufTicient height, fire was applied 

 to the top, and the bifmuth, as the heat penetrated through 

 the mafs, became melted, and trickled down into the hole 

 beneath, where it coUefted ia an irregular mafs ; being then 

 withdrawn, and broken into pieces, it was remelted in iron 

 or earthen pots, feparated from the impurities that floated 

 on ite furface, and finally caft into flat cakes, or loaves, for 

 fale. Another method was to divide a large pine tree lon- 

 gitudinally, and cut out the central part uf the wood, thus 



BIS 



forming it into a gutter ; this being placed fomewhat in- 

 clined, the ore was laid in the upper end, on a bed of chips 

 and fmall wood, fufiicient, when fet on fire, to liquify the 

 bifmuth, which, flowing down, was coUeftcd in a hole or 

 vcffel placed at the eiul of the trough. 



The fcarcity of wood has, however, put an end to thefc 

 rude and extravagant methods ; and the ores of bifmuth are 

 now reduced in a common reverberatoiy furnace, the bed of 

 which is lined with charcoal, whence the melted metal is re- 

 moved in iron ladles, and caft into maffes weighing twenty 

 or thirty pounds, in which ftate it is brought to market. 

 § 4. Externa] CharaSers and Phyfical Properties. 

 Bil'muth is a white metal with a reddifh yellow tinge ; is 

 confidcrably hard, but brittle, exhibiting a broad foliated 

 fradlure ; has a bright, almoll fpecular metallic luftre; and 

 is fomewhat fonorous, when ilruck. Though brittle, it 

 may be comprelTed ver)- confiderably by judicious hammer. 

 ing, and therefore varies greatly in its fpeeific gravity. Ac- 

 cording to MufchenbroccK, its fp.gr. when frelh melted, is 

 = 8.716; but when laminated, is = 9-638. Bergman 

 fixes its gravity at 9.67 ; and other authors make it as high 

 as 9.8, or even 10. The lamina:, of which this metal is 

 compofed, have but little adhefion to each other ; hence the 

 primitive form of its cryftals, which is that of a regular ofta- 

 hcdion, may very eafily be afcertained by diffeftion. It is 

 fufibie at 460° Fahr., and may be poured into a paper cone 

 without burning it. If, after it has begun to folidify, the 

 fluid part is poured off, a groupe of cryftals is obtained in 

 cubes, or reftangular volutes. When expofed in clofe vef- 

 fels to a violent heat, it fubhmes and attaches itfelf to the 

 cooler part of the apparatus in the form of brilliant 

 plates. 



§ 5. Oxyds of Bifmuth. 

 The combined aftion of air and moifture upon bifmuth, 

 at the ufual temperature, is very flight ; it becomes covered 

 with a reddifh grey fuperficial tarnifh, and afterwards ap- 

 pears to undergo no further change. At a melting heat, it 

 (hortly becomes covered with an iridefcent film, and by ex- 

 pofmg frefli fubllances to the air, is wholly converted into a 

 yellowifli blown oxyd, weighing about -j-y more than the 

 original metal. This oxyd melts into a yellow glafs at a 

 moderate red heat, and foon penetrates through the moft. 

 compadl earthen crucibles, though not quite fo eafily as 

 glais of lead does. When bifmuth is expofed to a ftrong 

 heat, with free acccfs of air, it burns wdth a faint blue 

 flame, and throws up at the fame time a copious white 

 oxyd, which was formerly caWdJlowers of bifmuth ; towards 

 the end of the proccfs the oxyd acquires fomewhat of a 

 yellowifh tinge, probably on account of a fmall portion of 

 fulphur, or other impurities. The glafs, or vitreous oxyd 

 of bifmuth, is a veiy ailive flux for earths and the more 

 difficultly fufible oxyds; on account, however, of thefuperior 

 cheapnefs and efficacy of lead, it is feldom ufed for this 

 purpofe. 



§ C. Jaion of Acids on Bifmuth. 

 I. Concentrated fulphuric acid has no aftion on bifmuth, 

 except when boiling hot ; in this ftate, it is rapidly decom- 

 pofed, giving out fulphureous acid gas, and reducing the 

 metal to a white pulverulent oxyd ; by a low red heat the 

 decompofition is fo complete, tliat a quantity of aftual ful- 

 phur is volatilized. The white mpfs being waftied with a 

 little warm water, parts with nearly the whole of its acid, 

 holding a fmall portion of bifmuth in folution : this fluid, 

 by careful evaporation, depofits minute foft cryftalline 

 needles of fulphat of bifmuth, from which, by the mere 

 affafion of water, the metal may be feparated in the form of 

 white oxyd. The fulphated oxyd, produced in the firil 



part 



