348 BISMUTH 



which wall there are as many fire-holes, h, as there are pipes in the furnaco ; t aro 

 iron pans which receive the fluid metal ; k, a. wooden water-trough, in which the 

 bismuth is granulated and cooled ; /, the posterior and higher-lying apertures of the 

 eliquation pipes, shut merely with a sheet-iron cover. The granulations of bismuth 

 drained from the posterior openings fall upon the flat surfaces m, and then into the 

 water-trough. aro draught-holes in the vault between the two pipes, which serve 

 for increasing or diminishing the heat at pleasure. 



The ores to be eliquated (sweated) are sorted by hand from the gangue, broken into 

 pieces about the size of a hazel nut, and introduced into the ignited pipes ; one charge 

 consisting of about cwt. ; so that the pipes are filled to half their diameter, and 

 three-fourths of their length. The sheet-iron door is shut, find the fire strongly xirged, 

 whereby the bismuth begins to flow in ten minutes, and falls through the holes in the 

 clay-plates into hot pans containing some coal-dust. Whenever it runs slowly, the 

 ore is stirred round in the pipes, at intervals during half an hour, in which time the 

 liquation is usually finished. The residuum, called bismuth barley ( Graupen), is 

 scooped out with iron rakes into a water-trough ; and the pipes are charged afresh ; 

 the pans, when full, have their contents cast into moulds, forming bars of from 25 to 

 50 Ibs. weight. About 20 cwt. of ore are smelted in 8 hours, with a consumption of 

 63 Leipsic cubic feet of wood. The bismuth thus procured by liquation upon the great 

 scale contains no small admixture of arsenic, iron, and some other metals, from which 

 it may bo freed by solution in nitric acid, precipitation by water, and reduction of the 

 sub-nitrate by black flux. By exposing the crude bismuth for some time to a dull 

 red heat, under charcoal, arsenic is expelled. 



Bismuth is also obtained as a by-product in treating certain ores of cobalt and 

 silver. A solution of the nitrate or chloride of bismuth is precipitated by addition 

 of water, and the basic salt thus obtained is dried and reduced with carbonate of soda 

 and charcoal. 



Bismuth is white, and resembles antimony, but has a reddish tint ; whereas the 

 latter metal has a bluish cast. It is brilliant, and crystallises readily in small cube- 

 like forms, often hollow, which are really rhombohedra, though long mistaken for true 

 cubes. The beautiful iridescence often seen on specimens of crystallised bismuth is pro- 

 duced artificially. The metal is very brittle, and may be easily reduced to powder. 

 Its specific gravity is 9'83 ; and it is said that by hammering it with care, the density 

 may be increased to 9*8827. It melts at 515 F. (268'3 C., Kiemsdijk), and may bo 

 cooled 6 or 7 below this point without fixing ; but the moment it begins to solidify, 

 the temperature rises to 480, and continues stationary till the whole mass is con- 

 gealed. Bismuth, like cast-iron, expands during solidification. 



When heated from 32 to 212, it expands ^ in length. When pure it affords a 

 very valuable means of adjusting the scale of high-ranged thermometers. At strong 

 heats bismuth volatilises, may bo distilled in close vessels, and is thus obtained in 

 crystalline laminae. 



Bismuth is readily soluble in nitric acid, but is almost unacted on by hydrochloric 

 or by sulphuric acid. 



Several alloys of bismuth are used in the arts. The alloy of bismuth and lead in 

 equal parts has a density of 10'709, being greater than the mean of the constituents ; 

 it has a foliated texture, is brittle, and of the same colour as bismuth. Bismuth, with 

 tin, forms a compound more elastic and sonorous than the tin itself, and is, therefore, 

 frequently added to it by the pe'vvterers. With 1 of bismuth and 24 of tin, the alloy 

 is somewhat malleable : with more bismuth it is brittle. When much bismuth is 

 present, it may be easily parted by strong muriatic acid, which dissolves the tin, and 

 leaves the bismuth in a black powder. It has been said that an alloy of tin, bismuth, 

 nickel, and silver hinders iron from rusting. 



The alloy of bismuth with tin and lead was first examined by Sir I. Newton, and 

 has been called ever since fusible metal. The French give to this alloy the name of 

 metal fusible de D'Arcet, and thus claim for him the merit of the discovery of it. 

 8 parts of bismuth, 5 of lead, and 3 of tin, melt at the moderate temperature of 

 202 F. ; but 2 of bismuth, 1 of lead, and 1 of tin, molt at 20075 F., according to 

 Kose. A small addition of mercury, or of cadmium, aids the fusibility. Such alloys 

 serve to take casts of anatomical preparations. The value of these bismuth-alloys for 

 taking casts is due in great measure to their expansion in cooling a sharp impression 

 being thus secured. Indeed, the behaviour of fusible metal on exposure to heat is 

 quite anomalous. It is said to dilate regularly from 32 to 95 F., then to contract 

 to 131, when it expands rapidly till it reaches 176, and from that point again 

 expands uniformly until it fuses. 



An alloy of 1 bismuth, 2 tin, and 1 load, is employed as a soft solder by tho 

 powterers ; tvnd the same has been proposed as a bath for tempering steel instruments. 

 Cake-moulds for the manufacture of toilet soaps are made of the same metal ; as also 



