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49. IndiumName: Indium
Indium is a very soft, silvery-white metal with a brilliant lustre. The pure metal gives a high-pitched "scream" when bent. It wets glass, as does gallium. It is useful for making low-melting alloys. An alloy of 24% indium and 76% gallium is liquid at room temperature. Canada produces the majority of of the world's supply of indium. Both gallium and indium are able to wet glass. One unusual property of indium is that it is very slightly radioactive; it very slowly decays by beta emission to tin over time. This radioactivity is not considered hazardous, mainly because its decay rate is nearly 50,000 times slower than that of natural thorium, with a half-life, 4 x 1014 years, many thousands of times longer than the estimated age of the universe. Also, indium is not a notorious cumulative poison, like its neighbor cadmium, and is relatively rare. Indium (named after the indigo line in its atomic spectrum) was discovered by Ferdinand Reich and Theodor Richter in 1863 while they were testing zinc ores with a spectrograph in search of thallium. Richter went on to isolate the metal in 1867. There is some unconfirmed evidence that suggests that indium has a low level of toxicity. However in the welding and semiconductor industries, where indium exposure is relatively high, there have been no reports of any toxic side-effects. Other sources are more definite about indium's toxicity. Quick links
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