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Science Innovation Centre · 019 · Potassium

This element is no longer available.

The name is derived from the English word potash. The chemical symbol K comes from kalium, the Mediaeval Latin for potash, which may have derived from the Arabic word qali, meaning alkali.

Potassium is a soft, silvery-white metal, member of the alkali group of the periodic chart. Potassium is silvery when first cut but it oxidizes rapidly in air and tarnishes within minutes, so it is generally stored under oil or grease. It is light enough to float into water with which it reacts instantly to release hydrogen, which burns with a lilac flame.

The chemistry of potassium is almost entirely that of the potassium ion, K+.

Most potassium (95%) goes into fertilizers and the rest goes mainly into making potassium hydroxide (KOH), by the electrolysis of potassium chloride solution, and then converting this to potassium carbonate (K2CO3). Potassium carbonate goes into glass manufacture, especially the glass used to make televisions, while potassium hydroxide is used to make liquid soaps and detergents. A little potassium chloride goes into pharmaceuticals, medical drips and saline injections.

Other potassium salts are used in baking, photography and tanning leather, and to make iodize salts. In all cases it is the negative anion, not the potassium, which is the key to their use.