Alloys are created by combining a metal with one or more additives, and the final product’s melting and evaporation temperatures, electrical conductivity, magnetic properties and other characteristics can be different from those of the original constituents. These changed properties often make the alloy useful to science or industry.
An example is a substance called Wood’s metal. Named after Barnabas Wood, who discovered it in 1860, it is an alloy of bismuth, lead, tin and cadmium. Today, it is marketed under a number of brands. For instance, Industrial Metal Supply Company offers a brand of Wood’s metal Phoenix customers like called Cerrobend.
Much of this alloy’s usefulness comes from its melting point, which is only 158 degrees F. This is unusual for a metal, most of which have very high melting points, making them dangerous and difficult to manipulate when molten.
This low melting point makes Wood’s metal useful for heat-sensitive switches in fire protection systems. Sprinkler systems have a part made from the metal to prevent the system’s switch from tripping at normal temperatures. If the heat rises to 158 degrees, this part melts, the switch trips and the sprinklers come on.
A related function is as safety releases for cylinders of compressed gas. All gas cylinders sold for medical use in the U.K. must have an emergency seal made of Wood’s metal. In a fire, this will melt before the cylinder gets hot enough to explode, releasing pressure and eliminating the risk.