A fusible metal is any alloy which melts at a temperature below that of boiling water, and below the arithmetic mean of the temperatures of fusion of the component parts—a feature especially marked with certain alloys of bismuth. Such alloys expand on cooling, and thus take fine impressions of molds. They are employed in electrotyping, in taking casts of medals and of woodcuts, in testing the finish of dies, for making anatomical casts and safety plugs for steam boilers, and in the construction of automatic fire sprinklers.
Examples are: Rose's alloy, composed of bismuth 2 parts, lead 1, tin 1; melts at 94 °C. (201 °F.). Wood's alloy, composed of bismuth 15 parts, tin 4, cadmium 3; melts at 60 °C. (140 °F.) Lifiowitz' alloy, composed of bismuth 15 parts, lead 8, tin 4, cadmium 3; melts at 65 °C. (149 °F.). D'Arcet's alloy, composed of bismuth 8 parts, lead 8, tin 3; melts at 79 °C. (174 °F.). Newton's alloy, composed of bismuth 8 parts, lead 5, tin 3; melts at 94.5 C. (202 °F.).
