Wood's Metal

You can play a very good party trick with this alloy of bismuth, lead, tin and cadmium, as it has such a low melting point that it will dissolve in a cup of tea. Don’t be tempted to drink it afterwards though, as lead and cadmium are very toxic accumulative substances! Because of the toxicity of cadmium and lead, an alternative to Wood’s metal has recently been invented called Field’s metal, a compound of bismith, tin and indium. However, indium is getting increasingly expensive and scarce due to the limitations of natural reserves and its large-scale use in LCD screens.

Because of this very low melting point, Wood’s metal is used as a low-temperature casting material, as solder for attaching other metals together, and as a fire-melted valve element to set off fire sprinkler systems in buildings. Because of its lead content, Wood’s metal is very dense and absorbs energy, so it is also used as a protective shield in radiotherapy to make sure only the area affected by cancer is treated.