Chemistry:Potassium chloride

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Short description: Potassium compound and alternative to salt
Not to be confused with Potassium chlorate.
"KCl" redirects here. For other uses, see KCL (disambiguation).
This page is about the salt. For the use of potassium chloride as a medication, see Potassium chloride (medical use). For the use of potassium in biology, see Potassium in biology.
Potassium chloride
Names
Other names
Identifiers
3D model (JSmol)
ChEBI
ChEMBL
ChemSpider
DrugBank
KEGG
RTECS number
  • TS8050000
UNII
Properties
KCl
Molar mass 74.555 g·mol−1
Appearance white crystalline solid
Odor odorless
Density 1.984 g/cm3
Melting point 770 °C (1,420 °F; 1,040 K)
Boiling point 1,420 °C (2,590 °F; 1,690 K)
27.77 g/100mL (0 °C)
33.97 g/100mL (20 °C)
54.02 g/100mL (100 °C)
Solubility Soluble in glycerol, alkalies
Slightly soluble in alcohol Insoluble in ether[1]
Solubility in ethanol 0.288 g/L (25 °C)[2]
Acidity (pKa) ~7
−39.0·10−6 cm3/mol
1.4902 (589 nm)
Structure
face centered cubic
Fm3m, No. 225
a = 629.2 pm[3]
Octahedral (K+)
Octahedral (Cl−)
Thermochemistry
83 J·mol−1·K−1[4]
−436 kJ·mol−1[4]
Pharmacology
1=ATC code }} A12BA01 (WHO) B05XA01 (WHO)
Oral, IV, IM
Pharmacokinetics:
Kidney: 90%; Fecal: 10%[5]
Hazards
Safety data sheet ICSC 1450
NFPA 704 (fire diamond)
NFPA 704 four-colored diamondFlammability code 0: Will not burn. E.g. waterHealth code 1: Exposure would cause irritation but only minor residual injury. E.g. turpentineReactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
0
1
0
Flash point Non-flammable
Lethal dose or concentration (LD, LC):
2600 mg/kg (oral, rat)[6]
Related compounds
Other anions
 Potassium fluoride
Potassium bromide
Potassium iodide
Other cations
 Lithium chloride
Sodium chloride
Rubidium chloride
Caesium chloride
Ammonium chloride
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
☒N verify (what is checkY☒N ?)
Infobox references

Potassium chloride (KCl, or potassium salt) is a metal halide salt composed of potassium and chlorine. It is odorless and has a white or colorless vitreous crystal appearance. The solid dissolves readily in water, and its solutions have a salt-like taste. Potassium chloride can be obtained from ancient dried lake deposits.[7] KCl is used as a salt substitute for table salt (NaCl), a fertilizer,[8] as a medication, in scientific applications, in domestic water softeners (as a substitute for sodium chloride salt), as a feedstock, and in food processing, where it may be known as E number additive E508.

It occurs naturally as the mineral sylvite, which is named after salt's historical designations sal degistivum Sylvii and sal febrifugum Sylvii,[9] and in combination with sodium chloride as sylvinite.[10]

Uses

Fertilizer

Potassium chloride, compacted, fertilizer grade

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.[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% K2O 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]

Medical use

Main article: Medicine:Potassium chloride (medical use)

Potassium is vital in the human body, and potassium chloride by mouth is the standard means to treat low blood potassium, although it can also be given intravenously. It is on the World Health Organization's List of Essential Medicines.[24] It is also an ingredient in Oral Rehydration Therapy (ORT)/solution (ORS) to reduce hypokalemia caused by diarrhoea,[25] which is also on the WHO's List of Essential Medicines.[24]

Potassium chloride contains 52% of elemental potassium by mass.[26]

Overdose causes hyperkalemia which can disrupt cell signaling to the extent that the heart will stop, reversibly in the case of some open heart surgeries.[27][28][29]

Culinary use

Potassium chloride can be used as a salt substitute for food, but because not everyone likes its flavor, it is often mixed with ordinary table salt (sodium chloride) to improve the taste, to form low sodium salt. The addition of 1 ppm of thaumatin considerably reduces this bitterness.[30] Complaints of bitterness or a chemical or metallic taste are also reported with potassium chloride used in food.[31]

The World Health Organization guideline Use 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]

Execution

In the United States, potassium chloride is used as the final drug in the three-injection sequence of lethal injection as a form of capital punishment. It induces cardiac arrest, ultimately killing the person.[35]

Industrial

Toxicity

The typical amounts of potassium chloride found in the diet appear to be generally safe.[36] In larger quantities, however, potassium chloride is toxic. The -1">50 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, the -1">50 of sodium chloride (table salt) is 3.75 g/kg.

Intravenously, the -1">50 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]

Chemical properties

Solubility

KCl is soluble in a variety of polar solvents.

Solubility[39]
Solvent Solubility
(g/kg of solvent at 25 °C)
Water 360
Liquid ammonia 0.4
Liquid sulfur dioxide 0.41
Methanol 5.3
Ethanol 0.37
Formic acid 192
Sulfolane 0.04
Acetonitrile 0.024
Acetone 0.00091
Formamide 62
Acetamide 24.5
Dimethylformamide 0.17–0.5

Solutions of KCl are common standards, for example for calibration of the electrical conductivity of (ionic) solutions, since KCl solutions are stable, allowing for reproducible measurements. In aqueous solution, it is essentially fully ionized into solvated K+
 and Cl−
 ions.

Redox and the conversion to potassium metal

Although potassium is more electropositive than sodium, 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 (see Le 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]

Other potassium chloride stoichiometries

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.

Physical properties

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 a lattice 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 lilac flame.

Production

Sylvite
Sylvinite

Potassium chloride is extracted from minerals sylvite, carnallite, and potash. It is also extracted from salt water and can be manufactured by crystallization from solution, flotation or electrostatic separation from suitable minerals. It is a by-product of the production of nitric acid from potassium nitrate and hydrochloric acid.

Most potassium chloride is produced as agricultural and industrial-grade potash in Saskatchewan, Canada, Russia, and Belarus. Saskatchewan alone accounted for over 25% of the world's potash production in 2017.[42]

Laboratory methods

Potassium chloride is inexpensively available and is rarely prepared intentionally in the laboratory. It can be generated by treating potassium hydroxide (or other potassium bases) with hydrochloric acid:

KOH + HCl → KCl + H
2O

This conversion is an acid-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:

2 K + Cl
2 → 2 KCl

References

  1. ↑ "Potassium chloride (PIM 430)". International Programme on Chemical Safety. 3.3.1 Properties of the substance. http://www.inchem.org/documents/pims/pharm/potasscl.htm. 
  2. ↑ "periodic-table-of-elements.org" (website shows values in g/100ml). https://periodic-table-of-elements.org/SOLUBILITY/potassium_chloride. 
  3. ↑ Alkali Halides: A Handbook of Physical Properties. Berlin: Springer. 2001. ISBN 978-3-540-42180-1. 
  4. ↑ 4.0 4.1 Chemical Principles 6th Ed.. Houghton Mifflin Company. 2009. p. A22. ISBN 978-0-618-94690-7. 
  5. ↑ "Compound Summary for Potassium Chloride". PubChem. U.S. National Library of Medicine. https://pubchem.ncbi.nlm.nih.gov/compound/4873. 
  6. ↑ "7447-40-7 - WCUXLLCKKVVCTQ-UHFFFAOYSA-M - Potassium chloride [USP:JAN"]. ChemIDplus. U.S. National Library of Medicine. https://pubchem.ncbi.nlm.nih.gov/#tab/sidsrcname=ChemIDplus&query=7447-40-7&input_type=text. 
  7. ↑ Descriptive inorganic chemistry (Sixth ed.). New York, NY: W. H. Freeman. 22 December 2013. ISBN 978-1-4641-2557-7. OCLC 882867766. 
  8. ↑ "Potassium Fertilizers (Penn State Agronomy Guide)". http://extension.psu.edu/agronomy-guide/cm/sec2/sec28c. 
  9. ↑ Watts, Henry (1883) (in en). A Dictionary of Chemistry and the Allied Branches of Other Sciences. Longmans, Green, and Company. https://books.google.com/books?id=d-bkUHqUZ5AC&pg=PA147. 
  10. ↑ 10.0 10.1 "Potassium and Potassium Alloys". Ullmann's Encyclopedia of Industrial Chemistry. 2006. doi:10.1002/14356007.a22_031.pub2. ISBN 978-3-527-30673-2. 
  11. ↑ Weil, Ray; Brady, Nyle (2022). The Nature and Properties of Soils. Pearson Education. ISBN 978-93-5606-271-9. 
  12. ↑ Manning, David A.C. (2010). "Mineral sources of potassium for plant nutrition. A review". Agronomy for Sustainable Development 30 (2): 281–294. doi:10.1051/agro/2009023. Bibcode: 2010AgSD...30..281M. https://hal.science/hal-00886529. 
  13. ↑ Havlin, John L.; Tisdale, Samuel L.; Nelson, Werner L.; Beaton, James D. (2016). Soil Fertility and Fertilizers: An Introduction to Nutrient Management. Pearson. ISBN 978-93-325-7034-4. 
  14. ↑ Nutrient Source Specifics: Potassium Chloride. Ref. No. 17 #13075. International Plant Nutrition Institute (IPNI). http://potassium.ipni.net/ipniweb/region/potassium.nsf/0/58AFA539CC03133085258178006F5140/$FILE/NSS-03%20PotassiumChloride.pdf. Retrieved 2024-11-24. 
  15. ↑ Havlin, John L.; Tisdale, Samuel L.; Nelson, Werner L.; Beaton, James D. (2014). "Potassium". Soil Fertility and Fertilizers (8th ed.). Pearson Education. pp. 186–188. ISBN 978-0-13-503373-9. https://www.pearson.com/us/higher-education/program/Havlin-Soil-Fertility-and-Fertilizers-8th-Edition/PGM334285.html. 
  16. ↑ 16.0 16.1 Manning, David A. C. (2010). "Mineral sources of potassium for plant nutrition. A review". Agronomy for Sustainable Development 30 (2): 281–294. doi:10.1051/agro/2009023. Bibcode: 2010AgSD...30..281M. https://link.springer.com/article/10.1051/agro/2009023. Retrieved 2024-11-24. 
  17. ↑ Mineral Commodity Summaries: Potash. United States Geological Survey (USGS). U.S. Department of the Interior.. https://pubs.usgs.gov/periodicals/mcs2024/mcs2024-potash.pdf. Retrieved 2024-11-24. 
  18. ↑ "Fertilizer Use by Crop". FAO Fertilizer and Plant Nutrition Bulletin.. Food and Agriculture Organization of the United Nations. https://openknowledge.fao.org/server/api/core/bitstreams/b66da618-027b-4124-a5c7-f870cd671484/content. Retrieved 2024-11-24. 
  19. ↑ Roy, Ram N.; Finck, Arnold; Blair, Graeme J.; Tandon, H.L.S. (2006). Plant Nutrition for Food Security: A Guide for Integrated Nutrient Management. FAO Fertilizer and Plant Nutrition Bulletin 16. Food and Agriculture Organization of the United Nations. pp. 141–142. ISBN 92-5-105490-8. http://www.fao.org/3/a0443e/a0443e00.htm. Retrieved 2024-11-24. 
  20. ↑ Brady, Nyle C.; Weil, Ray R. (2016). "Plant Nutrients and Nutrient Uptake". The Nature and Properties of Soils (15th ed.). Pearson Education. pp. 594–595. ISBN 978-0-13-325448-8. https://www.pearson.com/us/higher-education/program/Brady-Nature-and-Properties-of-Soils-The-15th-Edition/PGM203380.html. 
  21. ↑ Römheld, Volker; Kirkby, Ernest A. (2010). "Research on potassium in agriculture: needs and prospects". Plant and Soil 335 (1): 155–180. doi:10.1007/s11104-010-0520-1. Bibcode: 2010PlSoi.335..155R. https://link.springer.com/article/10.1007/s11104-010-0520-1. Retrieved 2024-11-24. 
  22. ↑ Xu, Xinxiang; Du, Xin; Wang, Fen; Sha, Jianchuan; Chen, Qian; Tian, Ge; Zhu, Zhanling; Ge, Shunfeng et al. (2020). "Effects of Potassium Levels on Plant Growth, Accumulation and Distribution of Carbon, and Nitrate Metabolism in Apple Dwarf Rootstock Seedlings". Frontiers in Plant Science 11. doi:10.3389/fpls.2020.00904. PMID 32655607. Bibcode: 2020FrPS...11..904X. 
  23. ↑ Chen, Yuhang; Yu, Manman; Zhu, Zaibiao; Zhang, Lixia; Guo, Qiaosheng (2013). "Optimisation of Potassium Chloride Nutrition for Proper Growth, Physiological Development and Bioactive Component Production in Prunella vulgaris L". PLOS ONE 8 (7). doi:10.1371/journal.pone.0066259. PMID 23874390. Bibcode: 2013PLoSO...866259C. 
  24. ↑ 24.0 24.1 World Health Organization model list of essential medicines: 21st list 2019. Geneva: World Health Organization. 2019. WHO/MVP/EMP/IAU/2019.06. License: CC BY-NC-SA 3.0 IGO. 
  25. ↑ World Health Organization; Unicef (2006). Oral rehydration salts: production of the new ORS. WHO/FCH/CAH/06.1. https://apps.who.int/iris/bitstream/handle/10665/69227/WHO_FCH_CAH_06.1.pdf. Retrieved 2024-11-14. 
  26. ↑ Zakiah, K.; Maulana, M. R.; Widowati, L. R.; Mutakin, J. (2021). "Applications of guano and K2CO3 on soil potential-P, potential-K on Andisols". IOP Conference Series: Earth and Environmental Science 648 (1). doi:10.1088/1755-1315/648/1/012185. Bibcode: 2021E&ES..648a2185Z. 
  27. ↑ "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. 20 April 2018. doi:10.1007/s10557-018-6783-0. PMID 29679302. 
  28. ↑ "Detection of Fatal Potassium Overdose: A Case Report and Review of the Literature". Diagnostics 13 (7): 1339. 4 April 2023. doi:10.3390/diagnostics13071339. PMID 37046560. 
  29. ↑ "Potassium levels and the risk of all-cause and cardiovascular mortality among patients with cardiovascular diseases: a meta-analysis of cohort studies". Nutr J 23 (1). 10 January 2024. doi:10.1186/s12937-023-00888-z. PMID 38195532. 
  30. ↑ New ingredients in food processing: biochemistry and agriculture. Boca Raton: CRC Press. 1999. p. 357. ISBN 978-1-85573-443-2. "... in dietary food containing potassium chloride, thaumatin added in the ratio of 1 ppm considerably reduces the sensation of bitterness. ..." 
  31. ↑ "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. September 2012. doi:10.1111/j.1750-3841.2012.02862.x. PMID 22901084. 
  32. ↑ Yamamoto, Rain (27 January 2025). "Overview of the WHO guideline on lower-sodium salt substitutes". World Health Organization. https://cdn.who.int/media/docs/default-source/nutrition-and-food-safety/events/2025/launch-of-lsss-guideline-presentation-1-overview.pdf. 
  33. ↑ "Use of lower-sodium salt substitutes: WHO guideline". World Health Organization. 27 January 2025. https://www.who.int/publications/i/item/9789240105591. 
  34. ↑ "Use of lower-sodium salt substitutes: WHO guideline". World Health Organization. 27 January 2025. https://iris.who.int/bitstream/handle/10665/380227/9789240105591-eng.pdf?sequence=1. 
  35. ↑ "Overview of Lethal Injection Protocols" (in en-US). https://deathpenaltyinfo.org/executions/lethal-injection/overview-of-lethal-injection-protocols. 
  36. ↑ Center for Food Safety and Applied Nutrition. "GRAS Substances (SCOGS) Database - Select Committee on GRAS Substances (SCOGS) Opinion: Potassium chloride" (in en). https://www.fda.gov/Food/IngredientsPackagingLabeling/GRAS/SCOGS/ucm261000.htm. 
  37. ↑ "Fatal poisoning by potassium in human and rabbit". Forensic Science 9 (1): 33–36. 1977-01-01. doi:10.1016/0300-9432(77)90062-0. PMID 838413. 
  38. ↑ "Molecular weight of KCl". https://www.convertunits.com/molarmass/KCl. 
  39. ↑ Metal Ions in Solution. New York: Ellis Horwood. 1978. ISBN 978-0-85312-027-8. 
  40. ↑ Zhang, Weiwei; Oganov, Artem R.; Zhu, Qiang; Lobanov, Sergey S.; Stavrou, Elissaios; Goncharov, Alexander F. (23 May 2016). "Stability of numerous novel potassium chlorides at high pressure". Sci Rep 6. doi:10.1038/srep26265. PMID 27211847. Bibcode: 2016NatSR...626265Z. 
  41. ↑ "Crystal structure of potassium chloride monohydrate: water intercalation into the B1 structure of KCl under high pressure". Acta Crystallographica Section C 78 (Pt 12): 749–754. December 2022. doi:10.1107/S2053229622011135. PMID 36468558. Bibcode: 2022AcCrC..78..749Y. 
  42. ↑ "Mineral Commodity Summaries". U.S. Geological Survey. January 2018. https://minerals.usgs.gov/minerals/pubs/commodity/potash/mcs-2018-potas.pdf. 

Further reading



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