Gallium Is a Metal That Melts in Your Hand

Most metals treat melting as a serious event that requires a furnace, protective gear and a great deal of patience. Gallium is not most metals. According to the Royal Society of Chemistry, it melts at 29.7646 degrees Celsius, or about 85.6 degrees Fahrenheit. Human body temperature is around 37 degrees, so a piece of gallium held in the hand melts. Hold a solid lump in your open palm and it slowly slumps into a small, shimmering silver puddle.

That is only half of its strange range. The Royal Society of Chemistry notes that it does not boil until well above 2,000 degrees Celsius, which gives it the largest liquid range of any material known. So a metal that turns liquid in your hand then stays liquid across a temperature range that would destroy almost anything else. It also has a habit shared with very few substances: like water, it expands when it freezes. The Royal Society of Chemistry points out that solid gallium even floats on the liquid, the way ice floats on water.

Gallium was predicted before it was found. The Royal Society of Chemistry explains that the Russian chemist Dmitri Mendeleev had already predicted an undiscovered element to sit below aluminium in his periodic table, and named it eka-aluminium. In 1875 the French chemist Paul-Émile Lecoq de Boisbaudran discovered it using spectroscopy. The Royal Society of Chemistry adds that he spotted a new violet line in the spectrum of zinc from ore mined in the Pyrenees. The name comes from Gallia, the Latin name for France, although the RSC points out a neat pun: Lecoq means rooster, and the Latin for rooster is gallus.

For all its theatrics, gallium has a darker side for one other metal. Liquid gallium wets surfaces very easily, and a materials group at the University of Cambridge shows what that does to aluminium: the gallium creeps into the boundaries between the metal’s crystal grains and pulls them apart, a process called liquid metal embrittlement. That is why it needs careful handling around aluminium. As for people, the Royal Society of Chemistry describes gallium as non-toxic with no known biological role, which compares well with mercury, the more famous liquid metal.

Gallium also does very grown-up work. According to the U.S. Geological Survey, integrated circuits account for 73 per cent of the gallium used in the United States, and devices such as LEDs, laser diodes and solar cells for another 26 per cent. Gallium arsenide and gallium nitride are used in high-speed circuits and in blue and violet LEDs, and the RSC lists red, blue and green LEDs, mobile phones and Blu-ray technology among its uses. Gallium arsenide solar cells, it adds, are much more efficient than ordinary silicon ones. Most gallium, the survey adds, is recovered as a by-product of processing bauxite, the ore of aluminium; a smaller share comes from zinc ores.

So the metal that melts on your palm is also sitting, solid and hard at work, inside a great deal of the technology around you. The only reason it stays solid in your phone is that the phone is usually cooler than you are.