The majority of the potassium chloride produced is used for makingfertilizer, calledpotash, since the growth of manyplants is limited by potassium availability.[11][12] The term "potash" refers to various mined and manufactured salts that contain potassium in water-soluble form. Potassium chloride sold as fertilizer is known as "muriate of potash"—it is the common name for potassium chloride (KCl) used in agriculture.[13][14][15][16] The vast majority of potash fertilizer worldwide is sold as muriate of potash.[17][18] The dominance of muriate of potash in the fertilizer market is due to its high potassium content (approximately 60%K 2O equivalent) and relative affordability compared to other potassium sources like sulfate of potash (potassium sulfate).[16][19] Potassium is one of the three primary macronutrients essential for plant growth, alongside nitrogen and phosphorus. Potassium plays a vital role in various plant physiological processes, including enzyme activation, photosynthesis, protein synthesis, and water regulation.[20][21] For watering plants, a moderate concentration of potassium chloride (KCl) is used to avoid potential toxicity: 6 mM (millimolar) is generally effective and safe for most plants, which is approximately 0.4 grams (0.014 oz) per liter of water.[22][23]
Potassium chloride can be used as asalt substitute forfood, but because not everyone likes itsflavor, it is often mixed with ordinarytable salt (sodium chloride) to improve thetaste, to formlow sodium salt. The addition of 1 ppm ofthaumatin considerably reduces this bitterness.[30] Complaints of bitterness or a chemical or metallic taste are also reported with potassium chloride used in food.[31]
TheWorld Health Organization guidelineUse of lower-sodium salt substitutes strongly recommends reducing sodium intake to less than 2 g/day and conditionally recommends replacing regular table salt with lower-sodium salt substitutes that contain potassium. This recommendation is intended for adults (not pregnant women or children) in general populations, excluding individuals with kidney impairments or with other circumstances or conditions that might compromise potassium excretion.[32][33][34]
In the United States, potassium chloride is used as the final drug in the three-injection sequence oflethal injection as a form ofcapital punishment. It inducescardiac arrest, ultimately killing the person.[35]
It is used as a supplement in animal feed to boost the potassium level in the feed. As an added benefit, it is known to increase milk production.[citation needed]
Glass manufacturers use granular potash as aflux, lowering the temperature at which a mixture melts. Because potash imparts excellent clarity to glass, it is commonly used in eyeglasses, glassware, televisions, and computer monitors.[citation needed]
Because natural potassium contains a tiny amount of the isotopepotassium-40, potassium chloride is used as abeta radiation source to calibrateradiation monitoring equipment. It also emits a relatively low level of 511 keV gamma rays from positron annihilation, which can be used to calibrate medical scanners.[citation needed]
Potassium chloride is used in somede-icing products designed to be safer for pets and plants, though these are inferior in melting quality tocalcium chloride. It is also used in various brands ofbottled water.[citation needed]
Potassium chloride is also an optical crystal with a wide transmission range from 210 nm to 20 μm. While cheap, KCl crystals arehygroscopic. This limits its application to protected environments or short-term uses such as prototyping. Exposed to free air, KCl optics will "rot". Whereas KCl components were formerly used forinfraredoptics, they have been entirely replaced by much tougher crystals such aszinc selenide.[citation needed]
The typical amounts of potassium chloride found in the diet appear to be generally safe.[36] In larger quantities, however, potassium chloride is toxic. TheLD50 of orally ingested potassium chloride is approximately 2.5 g/kg, or 190 grams (6.7 oz) for a body mass of 75 kilograms (165 lb). In comparison, theLD50 ofsodium chloride (table salt) is 3.75 g/kg.
Intravenously, theLD50 of potassium chloride is far smaller, at about 57.2 mg/kg to 66.7 mg/kg; this is found by dividing the lethal concentration of positive potassium ions (about 30 to 35 mg/kg)[37] by the proportion by mass of potassium ions in potassium chloride (about 0.52445 mg K+/mg KCl).[38]
Solutions of KCl are common standards, for example forcalibration of theelectrical conductivity of (ionic) solutions, since KCl solutions are stable, allowing for reproducible measurements. Inaqueous solution, it is essentially fully ionized into solvatedK+ andCl− ions.
Although potassium is moreelectropositive thansodium, KCl can be reduced to the metal by reaction with metallic sodium at 850 °C because the more volatile potassium can be removed by distillation (seeLe Chatelier's principle):
KCl(l) + Na(l) ⇌ NaCl(l) + K(g)
This method is the main method for producing metallic potassium.Electrolysis (used for sodium) fails because of the high solubility of potassium in molten KCl.[10]
Potassium chlorides with formulas other than KCl have been predicted to become stable under pressures of 20 GPa or more.[40] Among these, two phases of KCl3 were synthesized and characterized. At 20-40 GPa, a trigonal structure containing K+ and Cl3− is obtained; above 40 GPa this gives way to a phase isostructural with the intermetallic compound Cr3Si.[citation needed]
Under ambient conditions, the crystal structure of potassium chloride is like that of NaCl. It adopts a face-centered cubic structure known as the B1 phase with alattice constant of roughly 6.3 Å. Crystals cleave easily in three directions. Other polymorphic and hydrated phases are adopted at high pressures.[41]
Some other properties are
Transmission range: 210 nm to 20 μm
Transmittivity = 92% at 450 nm and rises linearly to 94% at 16 μm
Refractive index = 1.456 at 10 μm
Reflection loss = 6.8% at 10 μm (two surfaces)
dN/dT (expansion coefficient)= −33.2×10−6/°C
dL/dT (refractive index gradient)= 40×10−6/°C
Thermal conductivity = 0.036 W/(cm·K)
Damage threshold (Newman and Novak): 4 GW/cm2 or 2 J/cm2 (0.5 or 1 ns pulse rate); 4.2 J/cm2 (1.7 ns pulse rate Kovalev and Faizullov)
As with other compounds containing potassium, KCl in powdered form gives a lilacflame.
Most potassium chloride is produced as agricultural and industrial-grade potash inSaskatchewan, Canada, Russia, and Belarus. Saskatchewan alone accounted for over 25% of the world's potash production in 2017.[42]
Potassium chloride is inexpensively available and is rarely prepared intentionally in the laboratory. It can be generated by treatingpotassium hydroxide (or other potassium bases) withhydrochloric acid:
KOH + HCl → KCl + H2O
This conversion is anacid-base neutralization reaction. The resulting salt can then be purified by recrystallization. Another method would be to allow potassium to burn in the presence of chlorine gas, also a very exothermic reaction:
^Rayner-Canham G, Overton T (22 December 2013).Descriptive inorganic chemistry (Sixth ed.). New York, NY: W. H. Freeman.ISBN978-1-4641-2557-7.OCLC882867766.
^Havlin, John L.; Tisdale, Samuel L.; Nelson, Werner L.; Beaton, James D. (2016).Soil Fertility and Fertilizers: An Introduction to Nutrient Management. Pearson.ISBN978-93-325-7034-4.
^Mineral Commodity Summaries: Potash(PDF). United States Geological Survey (USGS). U.S. Department of the Interior.Archived(PDF) from the original on 2024-11-12. Retrieved2024-11-24.
^abWorld Health Organization (2019).World Health Organization model list of essential medicines: 21st list 2019. Geneva: World Health Organization.hdl:10665/325771. WHO/MVP/EMP/IAU/2019.06. License: CC BY-NC-SA 3.0 IGO.
^Hoppe LK, Muhlack DC, Koenig W, Carr PR, Brenner H, Schöttker B (20 April 2018). "Association of Abnormal Serum Potassium Levels with Arrhythmias and Cardiovascular Mortality: a Systematic Review and Meta-Analysis of Observational Studies".Cardiovasc Drugs Ther.32 (2):197–212.doi:10.1007/s10557-018-6783-0.PMID29679302.
^Lorient D, Linden G (1999).New ingredients in food processing: biochemistry and agriculture. Boca Raton: CRC Press. p. 357.ISBN978-1-85573-443-2.... in dietary food containing potassium chloride, thaumatin added in the ratio of 1 ppm considerably reduces the sensation of bitterness. ...
^Sinopoli DA, Lawless HT (September 2012). "Taste properties of potassium chloride alone and in mixtures with sodium chloride using a check-all-that-apply method".Journal of Food Science.77 (9):S319 –S322.doi:10.1111/j.1750-3841.2012.02862.x.PMID22901084.
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