Online Encyclopedia

Search over 40,000 articles from the original, classic Encyclopedia Britannica, 11th Edition.

BISMUTH

Online Encyclopedia
Originally appearing in Volume V04, Page 11 of the 1911 Encyclopedia Britannica.
» Make a correction to this article.
» Add information or comments to this article.
Spread the word: del.icio.us del.icio.us it!

BISMUTH , a metallic chemical See also:

element; See also:symbol Bi, atomic See also:weight 208.5 (0=16). It was probably unknown to the Greeks and See also:Romans, but during the See also:middle ages it became quite See also:familiar, notwithstanding its frequent confusion with other metals. In 1450 See also:Basil See also:Valentine referred to it by the name " wismut," and characterized it as a See also:metal; some years later See also:Paracelsus termed it " wissmat," and, in allusion to its brittle nature, affirmed it to be a " See also:bastard" or "See also:half-metal"; Georgius See also:Agricola used the See also:form " wissmuth," latinized to " bisemutum," and also the See also:term " plumbum cineareum." Its elementary nature was imperfectly understood; and the impure specimens obtained by the See also:early chemists explain, in some measure, its confusion with See also:tin, See also:lead, See also:antimony, See also:zinc and other metals; in 1595 Andreas Libavius confused it with antimony, and in 1675 See also:Nicolas See also:Lemery with zinc. These obscurities began to be finally cleared up with the researches of Johann Heinrich See also:Pott (1692-1777), a See also:pupil of See also:Stahl, published in his Exercitationes chemicae de Wismutho (1769), and of N. See also:Geoffroy, son of See also:Claude See also:Joseph Geoffroy, whose contribution to our knowledge of this metal appeared in the Memoires de l'academie francaise for 1753. Torbern Olof See also:Bergman reinvestigated its properties and deter-See also:mined its reactions; his See also:account, which was published in his Opuscula, contains the first fairly accurate description of the metal. - Ores and Minerals.—The See also:principal source of bismuth is the native metal, which is occasionally met with as a See also:mineral, usually in reticulated and arborescent shapes or as foliated and granular masses with a crystalline fracture. Although bismuth is readily obtained in See also:fine crystals by artificial means, yet natural crystals are rare and usually indistinct: they belong to the See also:rhombohedral See also:system and a See also:cube-like rhombohedron with interfacial angles of 92° 20' is the predominating form. There is a perfect cleavage perpendicular to the trigonal See also:axis of the crystals: the fact that only two (opposite) corners of the cube-like crystals can be truncated by cleavage at once distinguishes them from true cubes. When not tarnished, the mineral has a See also:silver-See also:white See also:colour with a tinge of red, and the lustre is metallic. Hardness 2-21; specific gravity 9.70-9'83. The slight See also:variations in specific gravity are due to the presence of small amounts of See also:arsenic, See also:sulphur or See also:tellurium, or to enclosed impurities.

Bismuth occurs in metalliferous See also:

veins' traversing See also:gneiss or See also:clay-See also:slate, and is usually associated with ores of silver and See also:cobalt. Well-known localities are See also:Schneeberg in See also:Saxony and Joachimsthal in Bohemia; at the former it has been found as arborescent See also:groups penetrating See also:brown See also:jasper, which material has occasionally been cut and polished for small ornaments. The mineral has been found in some Cornish mines and is fairly abundant in See also:Bolivia (near Sorata, and at Tasna in See also:Potosi). It is the See also:chief commercial source of bismuth. The See also:oxide, bismuth ochre, Bi2O3, and the sulphide, bismuth glance or See also:bismuthite, are also of commercial importance. The former is found, generally mixed with See also:iron, See also:copper and arsenic oxides, in Bohemia, See also:Siberia, See also:Cornwall, See also:France (Meymac) and other localities; it also occurs admixed with bismuth carbonate and See also:hydrate. The hydrated carbonate, bismutite, is of less importance; it occurs in Cornwall, Bolivia, See also:Arizona and else-where. Of the rarer bismuth minerals we may See also:notice the following:—the complex sulphides, copper bismuth glance or wittichenite, BiCu3S3, silver bismuth glance, bismuth cobalt See also:pyrites, bismuth See also:nickel pyrites or saynite, See also:needle ore (patrinite or aikinite), BiCuPbS3, emplectite, CuBiS2, and kobellite, BiAsPb3S6; the sulphotelluride See also:tetradymite; the selenide guanajuatite, Bi2Se3, walpurgite, Bi(UOz)3(OH)u(As04)4. Metallurgy.—Bismuth is extracted from its ores by dry, wet, or electro-metallurgical methods, the choice depending upon the See also:composition of the ore and economic conditions. The dry See also:process is more frequently practised, for the easy reducibility of the oxide and sulphide, together with the See also:low melting-point of the metal, renders it possible to effect a ready separation of the metal from the See also:gangue and impurities. The extraction from ores in which the bismuth is See also:present in the metallic See also:condition may be accomplished by a See also:simple liquation, or melting, in which the temperature is'just . sufficient to melt the bismuth, or by a See also:complete See also:fusion of the ore. The first process never extracts all the bismuth, as much as one-third being retained in the matte or speiss; the second is more satisfactory, since the extraction is more complete, and also allows the addition of reducing agents to decompose any admixed bismuth oxide or sulphide.

In the liquation process the ore is heated in inclined cylindrical retorts, and the molten metal is tapped at the See also:

lower end; the residues being removed from the upper end. The fusion process is preferably carried out in crucible furnaces; See also:shaft furnaces are unsatisfactory on account of the disintegrating See also:action of the molten bismuth on the See also:furnace linings. Sulphuretted ores are smelted, either with or without a preliminary calcination, with metallic iron; calcined ores may be smelted with See also:carbon (See also:coal). The reactions are strictly analogous to those which occur in the smelting of See also:galena (see LEAD), the carbon reducing any oxide, either present originally in the ore or produced in the calcination, and the iron combining with the sulphur of the bismuthite. A certain amount of bismuth sulphate is always formed during. the calcination; this is subsequently reduced to the sulphide and ultimately to the metal in the fusion. Calcination in reverberatory furnaces and a subsequent smelting in the same type of furnace with the addition of about 3 % of coal, See also:lime, soda and fluorspar, has been adopted for treating the Bolivian ores, which generally contain the sulphides of bismuth, copper, iron, antimony, lead and a little silver. The lowest layer of the molten See also:mass is principally metallic bismuth, the succeeding layers are a bismuth copper matte, which is subsequently worked up, and a slag. Ores containing the oxide and carbonate are treated either by smelting with carbon or by a wet process. In the wet process the ores, in which the bismuth is present as oxide or carbonate, are dissolved out with hydrochloric See also:acid, or, if the bismuth is to be extracted from a matte or alloy, the solvent employed is aqua regia or strong sulphuric acid. The See also:solution of metallic chlorides or sulphates so obtained is precipitated by iron, the metallic bismuth filtered, washed with See also:water, pressed in See also:canvas bags, and finally fused in See also:graphite crucibles, the See also:surface being protected by a layer of See also:charcoal. Another process consists in adding water to the solution and so precipitating the bismuth as oxychloride, which is then converted into the metal. The crude metal obtained by the preceding processes is generally contaminated by arsenic, sulphur, iron, nickel, cobalt and antimony, and sometimes with silver or See also:gold, A dry method of See also:purification consists in a liquation on a See also:hearth of See also:peculiar construction, which occasions the separation of the unreduced bismuth sulphide and the bulk of the other impurities.

A better process is to remelt the metal in crucibles with the addition of certain refining agents. The details of this process vary very considerably, being conditioned by the composition of the impure metal and the practice of particular See also:

works. The wet refining process is more tedious and expensive, and is only exceptionally employed, as in the See also:case of preparing the pure metal or its salts for pharmaceutical or chemical purposes. The basic nitrate is the See also:salt generally prepared, and, in See also:general outline, the process consists in dissolving the metal in nitric acid, adding water to the solution, boiling the precipitated basic nitrate with an See also:alkali to remove the arsenic and lead, dissolving the See also:residue in nitric acid, and reprecipitating as basic nitrate with water. J. F. W. Hampe prepared chemically pure bismuth by fusing the metal with See also:sodium carbonate and sulphur, dissolving the bismuth sulphide so formed in nitric acid, precipitating the bismuth as the basic nitrate, re-dissolving this salt in nitric acid, and then precipitating with See also:ammonia. The bismuth hydroxide so obtained is finally reduced by See also:hydrogen. Properties.—Bismuth is a very brittle metal with a white crystal-See also:line fracture and a characteristic reddish-white colour. It crystallizes in rhombohedra belonging to the hexagonal system, having interfacial angles of 87° 40'. According to G.

W. A. Kahlbaum, See also:

Roth and Siedler (Zeit. Anorg. Chem. 29, p. 294), its specific gravity is 9.78143; See also:Roberts and Wrightson give the specific gravity of solid bismuth as 9.82, and of molten bismuth as io•o55. It therefore expands on solidification; and as it retains this See also:property in a number of See also:alloys, the metal receives extensive application in forming type-metals. Its melting-point is variously given as 268.3° (F. Rudberg and A. D. von Riemsdijk) and 270.5° (C. C.

See also:

Person); commercial bismuth melts at 26o° (Ledebur), and electrolytic bismuth at 264° (Classen). It vaporizes in a vacuum at'292°, and its boiling-point, under atmospheric pressure, is between 1090° and 1450 (T. Carnelley and W. C. See also:Williams). See also:Regnault determined itsspecific See also:heat' between o and too to be 0.0308; Kahlbaum, Roth and Siedler (loc. cit.) give the value 0.03055. Its thermal conductivity is the lowest of all metals, being 18 as compared with silver as 3000; its coefficient of expansion between 0° and loo° is O'001234I Its See also:electrical conductivity is approximately 1.2, silver` at o° being talen as Too; it is the most diamagnetic substance known, and its thermoelectric properties render it especially voidable for the construction of thermopiles. The metal oxidizes very slowly in dry See also:air at See also:ordinary temperatures, but somewhat more rapidly in moist air or when heated. In the last case it becomes coated with a greyish-See also:black layer of an oxide (dioxide (?) ), at a red heat the layer consists of the trioxide (Big03); and is yellow or See also:green in the case of pure bismuth, and See also:violet or'See also:blue if impure ; at a See also:bright red heat it See also:burns with a bluish See also:flame to the trioxide. Bismuth combines directly with the See also:halogens, and the elements of the sulphur See also:group. It readily dissolves in nitric acid, aqua regia, and hot sulphuric acid, but tardily in hot hydrochloric acid. It is precipitated as the metal from solutions of its salts by the metals of the alkalis and alkaline earths, 'zinc; iron, copper, &c.

In its chemical See also:

affinities it resembles arsenic and antimony; an important distinction is that it forms no hydrogen ,See also:compound analogous to arsine and stibine. Alloys.—Bismuth readily forms alloys with other metals. Treated with sodammonium it yields a bluish-black mass,BiNa3, which takes See also:fire in the air and decomposes water. A brittle See also:potassium alloy` of silver-white colour and lamellar fracture is obtained by calcining 20 parts of bismuth with 16 of cream "of See also:tartar at a strong red heat. When present in other metals, even in very small quantity, bismuth renders them brittle and impairs their electrical conductivity' With See also:mercury it forms amalgams. Bismuth is a component of ma-Hy ternary alloys characterized by their low fusibility and expansion in solidification; many of them are used in 'the arts (see FusinpE 'METAL); -... , '. Compounds.—Bismuth forms four oxides, of which the trioxide, Bi2O3, is the most important. This compound occurs in nature as bismuth ochre, and may be prepared artificially by oxidizing the metal at a red heat, or by See also:heating the carbonate, nitrate' or hydrate. Thus obtained it is a yellow See also:powder, soluble in' the mineral acids to form soluble salts, which are readily precipitated as basic salts when the solution is diluted. It melt§ to a reddish-brown liquid, which solidifies to a yellow crystalline mass oncooling. The hydrate; Bi(OH)3, is obtained as a white powder by adding potash to a solution of a bismuth salt.

Bismuth dioxide, BiO or Bi202, is said to be formed by the limited oxidation of the metal, and as a brown precipitate by adding mixed solutions of bismuth and stannous chlorides to a solution of See also:

caustic potash. Bismuth tetroxide, Bi2O4„sometimes termed bismuth bismuthate, is obtained by melting bismuth,ttioxide with potash, or by igniting bismuth trioxide with potash and potassium chlorate. It is also formed 'by oxidizing bismuth trioxide suspended in caustic potash with See also:chlorine,'the pentoxide being formed simultaneously; oxidation and potassium ferricyanidesimply gives the tetroxide (See also:Hauser and Vanino, Zeit. Anorg. Chem., 1904, 39, p•38T)• The hydrate, Bi2O4.2H2O, is also known. Bismuth pentoxide, Bi2C5, is obtained by heating bismuthic acid, HBiO3, to530° C.; this acid (in the form of its salts) being the product of the continued oxidation of an alkaline solution of bismuth trioxide. Bismuth forms two chlorides: BiCl2 and BiC13. The dichloride, BiC12, is obtained as a brown crystalline powder by fusing the metal with the trichloride, or in a current of chlorine, or by heating the metal with See also:calomel to 25o°. Water decomposes it to metallic bismuth and the oxychloride, BiOCI. Bismuth trichloride, BiC13, was obtained by See also:Robert See also:Boyle by heating the metal with corrosive sublimate. It is the final product of burning bismuth in an excess of chlorine. It is a white substance, melting at 225°-230° and boiling at 435°–441°.

With excess of water, it gives a white precipitate of the oxychloride, BiOC1. Bismuth trichloride forms See also:

double compounds with hydrochloric acid, the chlorides of the alkaline metals, ammonia, nitric oxide and nitrosyl chloride. Bismuth &ifluoride, BiF3, a white powder, bismuth tribromide, BiBr3i See also:golden yellow crystals, bismuth iodide, BiI3r greyish-black crystals, are also known. These compounds closely resemble the trichloride in their methods of preparation and their properties, forming oxyhaloids with water, and double compounds with ammonia, &c. See also:Carbonates.—The basic carbonate, 2(BiO)2CO3•H2O, obtained as a white precipitate when an alkaline carbonate is added to a solution of bismuth nitrate, is employed in See also:medicine. Another basic carbonate, 3(BiO)2CO3.2Bi(OH)3.3H2O, constitutes the mineral bismutite. Nitrates.—The normal nitrate, Bi(NO3)i.5H20, is obtained in large transparent See also:asymmetric prisms by evaporating a solution of the metal in nitric acid. The action of water on this solution produces a crystalline precipitate of basic nitrate, probably Bi(OH)2NO3, though it varies with the amount of water employed. This precipitate constitutes the " magistery of bismuth " or " subnitrate of bismuth " of See also:pharmacy, and under the name of See also:pearl white, See also:blanc d'Espagne or blanc de fard has See also:long been used as a cosmetic. Sulphides.—Bismuth combines directly with 'sulphur to form, a disulphide, Bi2S2, and a trisulphide, Bi2S3, the latter compound being formed when the sulphur is in excess. A hydrated disulphide,' Bi2S2.2H2O, is obtained by passing sulphuretted hydrogen into a solution of bismuth nitrate and stannous chloride. Bismuth a the basic tellurate montanite, Biz(OH)4TeO4; the silicates rsenate displphide is a See also:grey metallic substance, which is decomposed by 'hydrochloric acid with the separation of metallic bismuth and the formation of bismuth trichloride.

Bismuth trisulphide, Bi2S3, constitutes the mineral bismuthite, and may be prepared by See also:

direct. See also:union of its constituents, or as a brown precipitate by passing sulphuretted hydrogen into a solution of a bismuth salt. It is, easily soluble in nitric acid. When heated to 200° it assumes the crystalline form of bismuthite. Bismuth forms several oxysulphides : Bi4O3S constitutes the mineral karelinite found at the Zavodinski mine in the See also:Altai ;Bi6OsSsand Bi3O,Shave been prepared artificially. Bismuth also forms the sulphohaloids, BiSC1, BiSBr, See also:BiSI, analogous to the oyxhaloids. Bismuth sulphate, Bi2(SO4)3, is obtained as a white powder by dissolving the metal or sulphide in concentrated sulphuric acid. Water decomposes it, giving a basic salt, Bix(SO4)(OH)s, which on heating gives (BiO)2SO.i. Other basic salts are known. ' 'Bismuth forms compounds similar to the trisulphide with the elements See also:selenium and tellurium. The tritelluride constitutes the mineral tetradymite, Bi2Te3. See also:Analysis.—Traces of bismuth may be detected by treating the solution with excess of ;tartaric acid, potash and stannous chloride, a precipitate or dark coloration of bismuth oxide being formed even when only one See also:part of bismuth is present in 20,000 of water. The. blackish brown sulphide precipitated from bismuth salts by sulphur etted hydrogen is insoluble in ammonium sulphide, but is readily dissolved by nitric acid.

The metal can be reduced by See also:

magnesium, Zinc, See also:cadmium, iron, tin, copper and substances like hypo-phosphorous acid' from acid solutions or from alkaline ones by formaldehyde. In quantitative estimations,it is generally weighed as oxide, after precipitation as sulphide or carbonate, or in the' metallic form, reduced as above. See also:Pharmacology.—The salts of bismuth are feebly antiseptic. Taken' internally the subnitrate, coming into contact with water, tends to decompose, gradually liberating nitric acid, one of the most, powerful See also:antiseptics. The See also:physical properties of the powder also give it a mild astringent action. There are no remote actions. DEerapeutics.—The subnitrate of bismuth :s invaluable in certain cases of See also:dyspepsia, and still more notably so in See also:diarrhoea. It owes its value to the decomposition described above, by means of which a powerful antiseptic action is safely and continuously exerted. There is hardly a safer See also:drug. It may be given in drachm doses with impunity. It See also:colours the faeces black owing to the formation of sulphide.

End of Article: BISMUTH

Additional information and Comments

There are no comments yet for this article.
» Add information or comments to this article.
Please link directly to this article:
Highlight the code below, right click, and select "copy." Then paste it into your website, email, or other HTML.
Site content, images, and layout Copyright © 2006 - Net Industries, worldwide.
Do not copy, download, transfer, or otherwise replicate the site content in whole or in part.

Links to articles and home page are always encouraged.

[back]
BISMILLAH 		[next]
BISMUTHITE

Site © 2006 - Net Industries