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Earth (historical chemistry)

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These rare-earth oxides are used as tracers to determine which parts of a watershed are eroding. Clockwise from top center: praseodymium, cerium, lanthanum, neodymium, samarium, and gadolinium. Rareearthoxides.jpg
These rare-earth oxides are used as tracers to determine which parts of a watershed are eroding. Clockwise from top center: praseodymium, cerium, lanthanum, neodymium, samarium, and gadolinium.

Earths were defined by the Ancient Greeks as "materials that could not be changed further by the sources of heat then available". [1] Several oxides were thought to be earths, such as aluminum oxide and magnesium oxide. [1] It was not discovered until 1808 that these are not elements but metallic oxides. [1] [2]

See also

References

  1. 1 2 3 Generalic, Eni. "History of the rare earth elements". www.periodni.com. Archived from the original on 12 August 2014. Retrieved 12 April 2020.
  2. ↑ "Alkaline-earth metal". Encyclopædia Britannica. Retrieved 18 April 2019. By the early 1800s it became clear that the earths, formerly considered to be elements, were oxides, compounds of a metal and oxygen.


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