Fertilizer

The majority of the potassium chloride produced is used for making fertilizer, called potash, since the growth of many plants is limited by potassium availability. The two main types of potash are: Muriate of Potash (MOP, Potassium Chloride) and Sulphate of Potash (SOP, Potassium Sulphate). While SOP typically sells at a premium to MOP, the vast majority of potash fertilizer worldwide is sold as MOP.

Medical use

This medication is a mineral supplement used to treat or prevent low amounts of potassium in the blood. A normal level of potassium in the blood is important. Potassium helps your cells, kidneys, heart, muscles, and nerves work properly. Most people get enough potassium by eating a well-balanced diet. Some conditions that can lower your body's potassium level include severe prolonged diarrhea and vomiting, hormone problems such as hyperaldosteronism, or treatment with "water pills"/diuretics.

Industrial

• As a chemical feedstock, it is used for the manufacture of potassium hydroxide and potassium metal. It is also used in medicine, lethal injections, scientific applications, food processing, soaps, and as a sodium-free substitute for table salt for people concerned about the health effects of sodium.
• It is used as a supplement in animal feed to boost the amount of nutrients in the feed, which in turn promotes healthy growth in animals. As an added benefit, it is known to increase milk production.
• It is sometimes used in water as a completion fluid in petroleum and natural gas operations, as well as being an alternative to sodium chloride in household water softener units.
• Glass manufactures use granular potash as a flux, lowering the temperature at which a mixture melts. Because potash confers excellent clarity to glass, it is commonly used in eyeglasses, glassware, televisions and computer monitors.
• Potassium chloride is used in some de-icing products that are designed to be safer for pets and plants, though these are inferior in melting quality to calcium chloride [lowest usable temperature 12 °F (−11 °C) v. −25 °F (−32 °C)]. It is also used in various brands of bottled water, as well as in bulk quantities for fossil fuel drilling purposes.
• Potassium chloride was once used as a fire extinguishing agent, used in portable and wheeled fire extinguishers.
• Along with sodium chloride and lithium chloride, potassium chloride is used as a flux for the gas welding of aluminium.
• Potassium chloride is also an optical crystal with a wide transmission range from 210 nm to 20 µm. While cheap, KCl crystal is hygroscopic.
• Potassium chloride has also been used to produce heat packs which employ exothermic chemical reactions, but these have mostly been discontinued with the advent of cheaper and more efficient methods, such as the oxidation of metals ('Hot Hands' one-time-use products) or the crystallization of sodium acetate (multiple-use products).