Chemical Element: potassium

(Modern Latin: named for potash, a compound of potassium; the symbol is from Latin kalium; from Arabic, gilf, and a reference to the charred ashes of the saltwort; metal)

Chemical-Element Information

Symbol: K
Atomic number: 19
Year discovered: 1807

Discovered by: Sir Humphry Davy (1778-1829), an English chemist.

  • Until the 18th century, no distinction was made between potassium and sodium.
  • This was because early chemists did not recognize that “vegetable alkali”, potassium carbonate (coming from deposits in the earth) and “mineral alkali”, sodium carbonate (derived from wood ashes) are distinct from each other. Eventually a distinction was made.
  • Potassium was isolated, in 1807, by Sir Humphry Davy, who obtained it through the electrolysis of very dry molten caustic potash (potassium hydroxide).
  • It was known that an electric current would break up water molecules into hydrogen and oxygen when more customary chemical methods failed.
  • Davy was interested in the problem and he constructed a battery with over two hundred fifty metallic plates, the strongest ever built up to that time.
  • On October 6, 1807, he passed an electric current through molten potassium carbonate and liberated a metal, which he called potassium.
  • Sir Davy coined the word “potassium”, a Latinized version of “potash”.
  • Potassium was the first metal isolated by electrolysis.
  • Davy isolated sodium by a similar procedure later in 1807.
  • Potassium is one of the most reactive of the metallic elements.
  • This property is illustrated when it is dropped into water; hydrogen is displaced and both the hydrogen and the potassium burst into flame, burning with a violet colored flame that usually culminates in a slight explosion.
  • To put it another way, little globules of shining metal, when added to water, tear the water molecules apart as the metal recombines with oxygen, and the liberated hydrogen is heated to the point where it bursts into flames.
  • It is important for the nutrition of plants, and its compounds are contained in most plant and animal tissues.
  • In the first decade of the 15th century, potassium salts were being produced in Scotland from the ashes of seaweed.

Name in other languages:

French: potassium

German: Kalium

Italian: potassio

Spanish: potasio

Additional information about potassium may be seen on this page.

Information about other elements may be seen at this Chemical Elements List.

A special unit about words that include chemo-, chem- may be seen here.