Potassium

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Potassium

This is potassium.

Symbol K
Atomic number 19
Atomic mass 39.0983 amu

Potassium metal was first isolated using an electrolysis apparatus in 1807. When electrodes were immersed in a bath of molten potassium hydroxide and a voltage was applied across the electrodes, liquid potassium metal collected around the cathode. A few months later, the same procedure was used to isolate sodium metal.

Distinguishing properties

Pure potassium metal is very soft. It reacts with the oxygen in dry air to produce a powerful oxidizing agent, potassium superoxide, K2O. In moist air, potassium hydroxide, KOH, is produced. Because of its instability in air, potassium is usually stored in kerosene.

Occurrence

Potassium chloride, KCl, occurs in many natural deposits. Enormous deposits are located in Saskatchewan, Canada. The fertilizer industry refers to any potassium salt as potash. The main salts used are the chloride, KCl, the nitrate, KNO3, and the sulphate, K2SO4.

Usage

Canada produces about 25% of the world production of potash from deposits in the Prairie Evaporite Formation in Saskatchewan.

Potash.gif

Shown here is potash ore which contains three minerals:

  1. milky-white crystals of potassium chloride,
  2. clear, colourless crystals of sodium chloride, and
  3. red-coloured clay.

Today agriculture consumes 95% of Canadian potash production. Potassium improves root and fibre growth as well as plant food production.

Common compounds

Listed below are the principal uses of potassium are in the form of compounds:

  • Potassium bromide, KBr, is extensively used in the manufacture of photographic plates, films, and papers.
  • Potassium chlorate, KClO3, is a powerful oxidizing agent. It is used in explosives, matches, weedkillers, fireworks, and disinfectant.
  • Potassium chloride, KCl, is the most abundant of potassium compounds. It is perhaps best known as a no-sodium table salt substitute. It is also an ingredient in many chemical fertilizers and is used in the manufacture of other chemicals.
  • Potassium hydroxide, KOH, is often called caustic potash. It is used in the manufacture of soaps and detergents. It is a good drain cleanser because it combines with grease (that clog drains) to form water soluble soaps.
  • Potassium carbonate, K2CO3, is used in the laboratory as a drying agent and industrially in the manufacture of soft soap, hard glass, and in the dyeing industry.
  • Potassium iodide, KI, is used in medicine, particularly in the treatment of goitre resulting from iodine deficiency.
  • Potassium nitrate, KNO3, is used in chemical fertilizers, in gunpowder and match heads.
  • Potassium permanganate, KMnO4, is a purple solid soluble in water. It is used in volumetric analysis as an oxidizing agent. It is also used as a bactericide and a disinfectant.
  • Potassium sulfate, K2SO4, is used as a fertilizer, particularly for tobacco plants, and in the chemical industry in the preparation of alums.
  • Potassium superoxide, K2O, is used in the respiratory equipment because it efficiently generates fresh oxygen while removing carbon dioxide.

See also

Periodic table of the elements