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FUSIBLE METAL

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Originally appearing in Volume V11, Page 369 of the 1911 Encyclopedia Britannica.
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FUSIBLE See also:

METAL , a See also:term applied to certain See also:alloys, generally composed of See also:bismuth, See also:lead and See also:tin, which possess the See also:property of melting at comparatively See also:low temperatures. See also:Newton's fusible metal (named after See also:Sir See also:Isaac Newton) contains 5o parts of bismuth, 31.25 of lead and 18.75 of tin; that of See also:Jean Darcet (1725-1801), 50 parts of bismuth with 25 each of lead and tin; and that of Valentin See also:Rose the See also:elder, 50 of bismuth with 28.1 of lead and 24.1 of tin. These melt between 9r° and 95° C. The addition of See also:cadmium gives still greater fusibility; in See also:Wood's metal, for instance, which is Darcet's metal with See also:half the tin replaced by cadmium, the melting point is lowered to 66°–71° C.; while another described by Lipowitz and containing 15 parts of bismuth, 8 of lead, 4 of tin and 3 of cadmium, softens at about 55° and is completely liquid a little above 6o°. By the addition of See also:mercury to Darcet's metal the melting point may be reduced so low as 45°. These fusible metals have the peculiarity of expanding as they cool; Rose's metal, for instance, remains pasty for a considerable range of temperature below its fusing point, contracts somewhat rapidly from 8o° to 55°, expands from 55° to 35°, and contracts again from 35° to 0°. For this See also:reason they may be used for taking casts of anatomical specimens or making cliches from wood-blocks, the expansion on cooling securing See also:sharp impressions. By suitable modification in the proportions of the components, a See also:series of alloys can be made which melt at various temperatures above the boiling point of See also:water; for example, with 8 parts of bismuth, 8 of lead and 3 of tin the melting point is 123°, and with 8 of bismuth, 30 of lead and 24 of tin it is 172°. With tin and lead only in equal proportions it is 241°. Such alloys are used for making the fusible plugs inserted in the See also:furnace-crowns of See also:steam boilers, as a safeguard in the event of the water-level being allowed to fall too low. When this happens the plug being no longer covered with water is heated to such a temperature that it melts and allows the contents of the See also:boiler to See also:escape into the furnace. In automatic See also:fire-sprinklers` the orifices of the pipes are closed with fusible metal, which melts and liberates the water when, owing to an outbreak of fire in the See also:room, the temperature rises above a predetermined limit.

End of Article: FUSIBLE METAL

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