potassium / potash

Both the name of and the element potassium, element number 19, are derived from potash. Potassium was isolated from potash by British chemist Humphry Davy in 1807, as recorded in the Philosophical Transactions of the Royal Society of that year:

Potassium and Sodium are the names by which I have ventured to call the two new substances.

The name is formed from the French word for potash, potasse + -ium1.

Potash was once literally ashes in a pot, the residue of burnt plant material. The word dates to the early 16th century. Over the centuries, exactly what is meant by potash has changed. Originally it was impure potassium carbonate obtained from the ashes of burnt plants; then as methods improved it denoted purer potassium carbonate. Senses over the years have included water with potassium salts and potassium hydroxide or caustic potash. In modern use, potash refers to any of the various salts of potassium, from whatever source, especially as used in fertilizer.

Potassium has the chemical symbol K, which is from the modern Latin kalium, formed from alkali.

1Oxford English Dictionary, potassium, 3rd Edition, December 2007, Oxford University Press, accessed 3 September 2009, http://dictionary.oed.com/cgi/entry/50185337.

2Oxford English Dictionary, potash, 3rd Edition, March 2009, Oxford University Press, accessed 3 September 2009, http://dictionary.oed.com/cgi/entry/50185328

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