Indium: a crying metal
Interesting facts about indium
Indium is a very soft metal. If you bend a piece of indium metal, it gives a high-pitched squeak. Once you’ve heard it, you’ll never forget it. This “cry” is caused by the disintegration and reorganization of crystals inside the metal. This phenomenon also arises when you bend tin, the neighboring element in the periodic table. Indium gets its name from the purple-indigo color of its spectral line, in Latin “Indicum”, or “indigo”, but the scientist who discovered it was colorblind!
How indium was discovered
It was discovered in 1863 by the German scientists Ferdinand Reich and Hieronymous Richter. Reich was studying the zinc ore sphalerite, which he hoped contained the recently discovered element of thallium. Using a spectroscope, he examined a sediment which was supposed to show the characteristic green line of thallium. Reich was colorblind, so he asked his colleague Richter to check the spectrum for him. The scientists were amazed. Inside of a green line, Richter found a bright blue line, which had not been seen before. Reich and Richter realized they had found a new element, and gave it the Latin name of “Indicum”, meaning “purple” or “indigo”. Reich and Richter even quarreled over who had discovered indium – Richter claimed that he was the sole discoverer of the element.
Richter went on to isolate the metal in 1864. At the World Fair in Paris in 1867, an indium ingot of 0.5 kg was presented.
Occurrence and application of indium
Pure metal indium can be found in nature, but it is mainly produced as a side product in zinc ore processing. Like gallium, indium can be applied to glass, and if it is allowed to settle, it forms a mirror, which is reflective like a silver mirror, but less corrosive. Indium is added to other metals to make hard alloys, some of which are used in dentistry, and in solder alloys of armored joints to prevent thermal fatigue.
The melting point of indium (429.7485 К or 156.5985 °C) is one of the reference points of the ITS-90 international temperature scale, the standard for determining temperature.
Indium is not used in the metabolism of living organisms, but in small doses its salts cause a rise in metabolism. If you swallow more than a few milligrams of indium salt, a toxic reaction will set in, affecting the heart, digestive tract and kidneys. The radioactive isotope In-111 radiates gamma radiation and is used in medical scans to detect such diseases as osteomyelitis (an acute or chronic bone infection) and decubitus, making it possible to carry out precise diagnosis and treatment.
This element did not have significant application until WWII, when it was used for coating bearings in high-performance aircraft. Today, it is used in LCD televisions and computer monitors in the form of indium tin oxide. It is a good conductor of electricity, which can send signals to individual pixels on the screen without light interference from other pixels. The production of indium has increased considerably in recent decades, and China is the world’s leading producer of it. Based on current rates of consumption, scientists predict that indium supplies are only sufficient for 13 years. So that humanity can continue to use televisions, computers and smartphones, additional recycling is required for the extraction of indium.
The Periodic Table A visual guide to the elements (p.118)