Earth (historical chemistry)

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 weren't elements but metallic oxides.^[1]^[2]

References

^ ^a ^b ^c Generalic, Eni. "History of the rare earth elements". www.periodni.com. Archived from the original on 12 August 2014. Retrieved 12 April 2020.
^ "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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[:0-1] 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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See also

References