potassium chloride

potassium chloride (KCl), ionic compound whose molecules consist of one potassium atom and one chlorine atom. It is a white-to-colourless face-centred cubic crystal.

Production

Potassium chloride can be extracted from sylvinite, a mineral mixture of sodium chloride (halite) and potassium chloride (sylvite), mined for potash, a mixture of potassium chloride and other potassium compounds. Potassium chloride is recovered from ores in Saskatchewan, Canada (which produces more than one-quarter of the world’s potash), and to a lesser extent from ores in New Mexico, U.S. It is refined from sylvite by using either fractional crystallization or the flotation process. In fractional crystallization, materials are refined based on differences in solubility. In the flotation process, air bubbles are injected into a flotation cell of potassium chloride crystals that are covered by surface-active materials. These air bubbles attach to the potassium chloride crystals, which generate a potassium chloride foam, and this foam is then mechanically separated by using a centrifuge.

In the refining of ores in Utah, water is used to help the process. The water dissolves the potassium chloride, and this solution is then pumped back to the surface, where the water evaporates, leaving the potassium chloride.

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Uses

Potassium chloride is most often used in potash as part of an effective fertilizer for plants. Approximately 90 percent of all potassium chloride manufactured is used in the fertilizer industry. Other uses include industrial, pharmaceutical, and food and beverage applications.

In medicine it is used to treat or prevent low levels of potassium (hypokalemia) in the human body. Potassium ions are needed for proper functioning of the heart, muscles, kidneys, and nervous and digestive systems.

Potassium chloride can be substituted for salt (sodium chloride) in water softeners and in processes related to food processing. For people with high blood pressure, potassium chloride can be used as a salt substitute in food. Potassium chloride is added to sodium chloride in table salt instead of using pure potassium chloride. (Potassium chloride does not have as salty a taste as sodium chloride.) A small substitution of potassium chloride into table salt helps reduce sodium intake for people worried about the health effects of too much sodium in their diet.

Potassium chloride is often added to animal feed to increase milk production in cows and goats.

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When aluminum is to be welded, potassium chloride is used in the flux between the two pieces of metal.

Chemical and physical properties

Potassium chloride has a molecular mass of 74.551 grams per mole, a solubility in water of 253.9 grams per litre at 20 °C (68 °F), and a density of 1.984 grams per millilitre. It is odourless and has a slightly sour taste. The melting point is 770 °C (1,418 °F), and the boiling point is 1,420 °C (2,588 °F).

Potassium chloride readily dissolves in water, and the aqueous solution that forms is a good conductor of electricity. Potassium chloride produces a lilac or pale violet colour when it burns. While it is not directly used in fireworks, potassium chloride is used to manufacture other chemicals used in pyrotechnics, such as potassium chlorate and potassium perchlorate.