FUSIBLE METAL. A term applied to cer tain metallic alloys characterized by the rela tively low temperatures at which they melt. Among the more important of these alloys are d'Arcet's metal, Rose's metal, Wood's metal, and Lipowitz's metal. D'Arcet's metal consists of 8 parts of bismuth, 8 parts of lead, and 3 parts of tin; it melts at 79° C. (174.2° F.). Rose's metal consists of 1 part of lead, 1 part of tin, and 2 parts of bismuth; it melts at 94° C. (201.2° F.). Wood's metal consists of 4 parts of tin, 3 parts of cadmium, and 15 parts of bis muth; it melts at 60° C. (140° F.). Lipowitz's metal consists of 8 parts of lead, 4 parts of tin, 3 parts of cadmium, and 15 parts of bismuth; it melts at 65° C. (149° F.). Of course, by varying the relative composition of these alloys a variety of other fusible metals may be obtained, and the melting-points of these may be made to answer the purposes for which they are intended.
For example, the constituents of d'Arcet's metal may be mixed in the proportion of 5 parts of lead, 8 parts of bismuth, and 3 parts of tin, and then the melting-point will be 94.5° C. (202.1° F.). Many fusible metals, especially d'Arcet's, have the property of expanding as they cool, while still soft, and are therefore used for tak ing proof impressions of dies, each line being exactly reproduced in the cast made of the alloy. Fusible metals have also been employed for mak ing safety plugs for boilers. When the steam reaches a pressure corresponding to the melting point of the alloy, the plug gives way and the steam escapes. It is found, however, that the melting-point of the alloys is liable to change, and hence these metallic safety plugs are hardly reliable. See MELTING-POINT.