 Discovery Information
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| Who: Sir Humphrey Davy |
| When: 1807 |
| Where: England |
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| Name Origin
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| From potash (pot ash); K from latin: kalium |
| "Potassium" in different languages. |
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| Sources
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| Found in minerals like carnallite [(KMgCl3).6H2O] and sylvite (KCl). Potassium makes up about 2.40% of the weight of the Earth's crust, it is the seventh most abundant element.
The main sources of potash are mined in USA (California, New Mexico and Utah) and Germany. Around 200 tons are produced annually.
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| Abundance
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| Universe: 3 ppm (by weight) |
| Sun: 4 ppm (by weight) |
| Carbonaceous meteorite: 710 ppm |
| Earth's Crust: 15000 ppm |
| Human: |
| 2 x 106 ppb by weight
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| 3.2 x 105 ppb by atoms
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| Uses
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| Used as potash (potassium carbonate) in making glass, soap, lenses and salt substitute. Also as potassium nitrate (KNO3, also called saltpeter) it is used to make explosives and to colour fireworks in mauve.
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| Glass treated with liquid potassium is much stronger than regular glass. |
| Potassium chloride (KCl) is used as a substitute for table salt and is also used to stop the heart, e.g. in cardiac surgery
and in executions by lethal injection in solution.
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| History
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| Potassium was discovered in 1807 by Sir Humphry Davy, who derived it from caustic potash (KOH). Potassium was the first metal that was isolated by electrolysis.
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| Notes
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| Potassium is the second least dense metal; only lithium is less dense. It is a soft, low-melting solid that can easily be
cut with a knife. Freshly cut potassium is silvery in appearance, but in air it begins to tarnish toward grey immediately.
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| Potassium is a necessary mineral in daily nutrition; it assists in muscle contraction and in maintaining fluid and electrolyte
balance in body cells.
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| Formerly called kalium hence the symbol 'K'. |
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| Hazards
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| Solid potassium reacts violently with water, and should therefore be kept under a mineral oil such as kerosene and handled
with care. When in water, it may catch fire spontaneously, burning with a purple flame. Unlike lithium and sodium however, potassium cannot be stored under oil indefinitely. If stored longer than 6 months to a year, dangerous shock-sensitive
peroxides can form on the metal and under the lid of the container that can detonate upon opening.
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| Potassium is very harmful by ingestion or through the skin or eye contact, it may cause irreversible eye damage. |
