BISMUTH is a brittle white metal with a slight tint of red: its specific gravity is 9.822 (Hatchett, Phill Trans. 1808.) It fuses at 476o (Crchton) 507o.
(Rudberg), and always crystallises on cooling. According to Chaudet, pure bismuth is somewhat flexible. A cast bar of the metal (see Rennie), one-tenth of an inch diameter, supports, according to Muschenbroeck, a weight of forty-eight pounds. Bismuth is volatile at a high heat, and may be distilled in close vessels. It transmits heat more slowly than most other metals, perhaps in consequence of its texture. (Brande, 861.)
Bismuth is scarcely used alone, but it is employed for imparting fusibility to alloys, thus:
8 bismuth, 5 lead, 3 tin, constitute Newton's fusible alloy, which melts at 212° F.
2 bismuth, 1 lead, 1 tin, Rose's fusible alloy, which melts at 201° F.
5 bismuth, 3 lead, 2 tin, when combined melt at 199°.
8 bismuth, 5 lead, 4 tin, 1 type-metal, constitute the fusible alloy used on the Continent for producing the beautiful casts of the French medals, by the clichie process. The metals should be repeatedly melted and poured into drops until they are well mixed. Mr. Charles V. Walker substituted antimony for the type-metal, and strongly recommends this latter in preference to the first-named fusible alloy. Electrotype Manipulation, Part II. pp. 9 - 11, where the clichee process is described.
1 bismuth and 2 tin make the alloy Mr. Cowper found to be the most suitable for rose-engine and eccentric-turned patterns, to be printed from after the manner of letter-press. He recommends the thin plates to be cast upon a cold surface of metal or stone, upon which a piece of smooth paper is placed, and then a metal ring; the alloy should neither burr nor crumble; if proper, it turns soft and silky; when too crystalline, more tin should be added.
constitute pewterers' soft solders.
All these alloys must be cooled quickly to avoid the separation of the bismuth; they are rendered more fusible by a small addition of mercury.