SCIENCE
On a bitterly cold afternoon, my friend invited me in for tea. My host provided a piping hot cup and slid the bowl of sugar and a metal spoon towards me. I scooped a liberal helping of sugar into the tea, and began to stir with the spoon. One stir, then two. By three the spoon had disappeared.
I stared, perplexed, into the dark abyss of the tea. I just had a spoon in my hand, right? After a careful sniff, I confirmed that the liquid I held was indeed tea, not acid. As the laughter started, I knew I had been treated to a practical joke, courtesy of a chemist.
The metallic spoon was made of gallium (Ga), a silvery, soft metal that sits in the third row of the periodic table, with atomic number 31 (indicating that it has 31 protons). Unlike most metals, gallium melts at about 86 °F, low enough to melt in human hands — or in this case, to melt in tea.
Only a few other metals, including mercury, caesium and rubidium, can exist as a liquid at or near room temperatures. Of these, gallium is the most friendly to handle, as it is considered non-toxic. Mercury is highly toxic, while caesium and rubidium will react violently with water.
As a solid, pure gallium is brittle and a poor electrical conductor. However when gallium is combined with other elements, it becomes a versatile tool for the technology age.
Used in electronics, gallium arsenide and gallium nitride account for the vast majority of gallium consumption. These gallium compounds are implemented in numerous electronic components, including semiconductors, blue and violet light-emitting diodes (LEDs), diode lasers (like those found in Blu-ray players) and solar panels. Gallium was also added to stabilize the explosive plutonium in the cores of the first and third nuclear bombs.
Although not normally found in the human body, gallium has also become an important tool in medicine. Gallium ions are trafficked similarly to iron ions in the body. It accumulates at inflammation sites, where it acts as a marker for diagnosis and disease treatment.
The radioactive isotope of gallium (67Ga) is used for positron emission tomography or PET scanning. As the radioactive element moves through the body under the vision of the PET scanner, it emits energy displayed in three-dimensional images that help doctors spot unusual processes or abnormal tissues.
Beyond its uses as a party trick, gallium has become an extremely important element for modern technology and disease diagnosis. In the end, I requested a new cup of tea. When the original tea cooled, the gallium was collected to be remolded into a spoon again, ready to be used on another unsuspecting guest.
