Potassium chloride (KCl, or potassium salt) is a
metal halide
Metal halides are compounds between metals and halogens. Some, such as sodium chloride are ionic, while others are covalently bonded. A few metal halides are discrete molecules, such as uranium hexafluoride, but most adopt polymeric structures, ...
salt
Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of salts; salt in the form of a natural crystalline mineral is known as rock salt or halite. Salt is present in vast quantitie ...
composed of
potassium
Potassium is the chemical element with the symbol K (from Neo-Latin ''kalium'') and atomic number19. Potassium is a silvery-white metal that is soft enough to be cut with a knife with little force. Potassium metal reacts rapidly with atmosphe ...
and
chlorine
Chlorine is a chemical element with the Symbol (chemistry), symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate betwee ...
. It is
odor
An odor (American English) or odour (English in the Commonwealth of Nations, Commonwealth English; American and British English spelling differences#-our, -or, see spelling differences) is caused by one or more volatilized chemical compounds ...
less and has a white or
color
Color (American English) or colour (British English) is the visual perceptual property deriving from the spectrum of light interacting with the photoreceptor cells of the eyes. Color categories and physical specifications of color are associ ...
less
vitreous crystal
A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macros ...
appearance. The solid dissolves readily in water, and its
solution
Solution may refer to:
* Solution (chemistry), a mixture where one substance is dissolved in another
* Solution (equation), in mathematics
** Numerical solution, in numerical analysis, approximate solutions within specified error bounds
* Soluti ...
s have a
salt
Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of salts; salt in the form of a natural crystalline mineral is known as rock salt or halite. Salt is present in vast quantitie ...
-like taste. Potassium chloride can be obtained from ancient dried lake deposits. KCl is used as a fertilizer, in
medicine
Medicine is the science and practice of caring for a patient, managing the diagnosis, prognosis, prevention, treatment, palliation of their injury or disease, and promoting their health. Medicine encompasses a variety of health care pract ...
, in scientific applications, domestic
water softener
Water softening is the removal of calcium, magnesium, and certain other metal cations in hard water. The resulting soft water requires less soap for the same cleaning effort, as soap is not wasted bonding with calcium ions. Soft water also exten ...
s (as a substitute for
sodium chloride
Sodium chloride , commonly known as salt (although sea salt also contains other chemical salts), is an ionic compound with the chemical formula NaCl, representing a 1:1 ratio of sodium and chloride ions. With molar masses of 22.99 and 35.45 g ...
salt), and in
food processing
Food processing is the transformation of agricultural products into food, or of one form of food into other forms. Food processing includes many forms of processing foods, from grinding grain to make raw flour to home cooking to complex industr ...
, where it may be known as
E number
E numbers ("E" stands for "Europe") are codes for substances used as food additives, including those found naturally in many foods such as vitamin C, for use within the European Union (EU) and European Free Trade Association (EFTA). Commonly ...
additive E508.
It occurs naturally as the
mineral
In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. ( ...
sylvite, and in combination with
sodium chloride
Sodium chloride , commonly known as salt (although sea salt also contains other chemical salts), is an ionic compound with the chemical formula NaCl, representing a 1:1 ratio of sodium and chloride ions. With molar masses of 22.99 and 35.45 g ...
as
sylvinite
Sylvinite is a sedimentary rock made of a mechanical mixture of the minerals sylvite (KCl, or potassium chloride) and halite (NaCl, or sodium chloride).Weiss N.L., SME Mineral Processing Handbook 1985, Page 22-2 Sylvinite is the most important s ...
.
[
]
Uses
Fertilizer
The majority of the potassium chloride produced is used for making fertilizer
A fertilizer (American English) or fertiliser (British English; see spelling differences) is any material of natural or synthetic origin that is applied to soil or to plant tissues to supply plant nutrients. Fertilizers may be distinct from ...
, called potash
Potash () includes various mined and manufactured salts that contain potassium in water-soluble form. , since the growth of many plant
Plants are predominantly photosynthetic eukaryotes of the kingdom Plantae. Historically, the plant kingdom encompassed all living things that were not animals, and included algae and fungi; however, all current definitions of Plantae exclud ...
s is limited by potassium availability. Potassium chloride sold as fertilizer is known as muriate
In chemistry, a hydrochloride is an acid salt resulting, or regarded as resulting, from the reaction of hydrochloric acid with an organic base (e.g. an amine). An alternative name is chlorhydrate, which comes from French. An archaic alternative na ...
of potash (MOP). The vast majority of potash fertilizer worldwide is sold as MOP.
Medical use
Potassium is vital in the human body
The human body is the structure of a Human, human being. It is composed of many different types of Cell (biology), cells that together create Tissue (biology), tissues and subsequently organ systems. They ensure homeostasis and the life, viabi ...
, and potassium chloride by mouth is the common means to treat low blood potassium
Hypokalemia is a low level of potassium (K+) in the blood serum. Mild low potassium does not typically cause symptoms. Symptoms may include feeling tired, leg cramps, weakness, and constipation. Low potassium also increases the risk of an abnor ...
, although it can also be given intravenously. It is on the World Health Organization's List of Essential Medicines
The WHO Model List of Essential Medicines (aka Essential Medicines List or EML), published by the World Health Organization (WHO), contains the medications considered to be most effective and safe to meet the most important needs in a health ...
. Overdose causes hyperkalemia
Hyperkalemia is an elevated level of potassium (K+) in the blood. Normal potassium levels are between 3.5 and 5.0mmol/L (3.5 and 5.0mEq/L) with levels above 5.5mmol/L defined as hyperkalemia. Typically hyperkalemia does not cause symptoms. Occasi ...
which can disrupt cell signaling to the extent that the heart will stop, reversibly in the case of some open heart surgeries.
Culinary use
It can be used as a salt substitute
A salt substitute, also known as low-sodium salt, is a low-sodium alternative to edible salt (table salt) marketed to circumvent the risk of high blood pressure and cardiovascular disease associated with a high intake of sodium chloride while main ...
for food
Food is any substance consumed by an organism for nutritional support. Food is usually of plant, animal, or fungal origin, and contains essential nutrients, such as carbohydrates, fats, proteins, vitamins, or minerals. The substance is inge ...
, but due to its weak, bitter, unsalty flavor
Flavor or flavour is either the sensory perception of taste or smell, or a flavoring in food that produces such perception.
Flavor or flavour may also refer to:
Science
*Flavors (programming language), an early object-oriented extension to Lis ...
, it is often mixed with ordinary table salt (sodium chloride) to improve the taste
The gustatory system or sense of taste is the sensory system that is partially responsible for the perception of taste (flavor). Taste is the perception produced or stimulated when a substance in the mouth reacts chemically with taste receptor ...
to form low sodium salt. The addition of 1 ppm of thaumatin
Thaumatin (also known as talin) is a low-calorie sweetener and flavor modifier. The protein is often used primarily for its flavor-modifying properties and not exclusively as a sweetener.
The thaumatins were first found as a mixture of prote ...
considerably reduces this bitterness. Complaints of bitterness or a chemical or metallic taste are also reported with potassium chloride used in food.
Industrial
As a chemical feedstock
A raw material, also known as a feedstock, unprocessed material, or primary commodity, is a basic material that is used to produce goods, finished goods, energy, or intermediate materials that are feedstock for future finished products. As feedst ...
, it is used for the manufacture of potassium hydroxide
Potassium hydroxide is an inorganic compound with the formula K OH, and is commonly called caustic potash.
Along with sodium hydroxide (NaOH), KOH is a prototypical strong base. It has many industrial and niche applications, most of which exp ...
and potassium
Potassium is the chemical element with the symbol K (from Neo-Latin ''kalium'') and atomic number19. Potassium is a silvery-white metal that is soft enough to be cut with a knife with little force. Potassium metal reacts rapidly with atmosphe ...
metal. It is also used in medicine, lethal injection
Lethal injection is the practice of injecting one or more drugs into a person (typically a barbiturate, paralytic, and potassium solution) for the express purpose of causing rapid death. The main application for this procedure is capital puni ...
s, scientific
Science is a systematic endeavor that builds and organizes knowledge in the form of testable explanations and predictions about the universe.
Science may be as old as the human species, and some of the earliest archeological evidence for ...
applications, food processing
Food processing is the transformation of agricultural products into food, or of one form of food into other forms. Food processing includes many forms of processing foods, from grinding grain to make raw flour to home cooking to complex industr ...
, soap
Soap is a salt of a fatty acid used in a variety of cleansing and lubricating products. In a domestic setting, soaps are surfactants usually used for washing, bathing, and other types of housekeeping. In industrial settings, soaps are use ...
s, and as a sodium-free substitute for table salt
Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of salts; salt in the form of a natural crystalline mineral is known as rock salt or halite. Salt is present in vast quantitie ...
for people concerned about the health effects of sodium.
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.
It is sometimes used in solution as a completion fluid in petroleum
Petroleum, also known as crude oil, or simply oil, is a naturally occurring yellowish-black liquid mixture of mainly hydrocarbons, and is found in geological formations. The name ''petroleum'' covers both naturally occurring unprocessed crud ...
and natural gas
Natural gas (also called fossil gas or simply gas) is a naturally occurring mixture of gaseous hydrocarbons consisting primarily of methane in addition to various smaller amounts of other higher alkanes. Low levels of trace gases like carbo ...
operations, as well as being an alternative to sodium chloride
Sodium chloride , commonly known as salt (although sea salt also contains other chemical salts), is an ionic compound with the chemical formula NaCl, representing a 1:1 ratio of sodium and chloride ions. With molar masses of 22.99 and 35.45 g ...
in household water softener
Water softening is the removal of calcium, magnesium, and certain other metal cations in hard water. The resulting soft water requires less soap for the same cleaning effort, as soap is not wasted bonding with calcium ions. Soft water also exten ...
units.
Glass manufacturers use granular potash as a flux
Flux describes any effect that appears to pass or travel (whether it actually moves or not) through a surface or substance. Flux is a concept in applied mathematics and vector calculus which has many applications to physics. For transport ph ...
, 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.
KCl is useful as a beta radiation
A beta particle, also called beta ray or beta radiation (symbol β), is a high-energy, high-speed electron or positron emitted by the radioactive decay of an atomic nucleus during the process of beta decay. There are two forms of beta decay, β∠...
source for calibration
In measurement technology and metrology, calibration is the comparison of measurement values delivered by a device under test with those of a calibration standard of known accuracy. Such a standard could be another measurement device of know ...
of radiation monitoring equipment Radiation dosimetry in the fields of health physics and radiation protection is the measurement, calculation and assessment of the ionizing radiation dose absorbed by an object, usually the human body. This applies both internally, due to ingested ...
, because natural potassium contains 0.0118% of the isotope
Isotopes are two or more types of atoms that have the same atomic number (number of protons in their nuclei) and position in the periodic table (and hence belong to the same chemical element), and that differ in nucleon numbers (mass numbers) ...
40K. One kilogram
The kilogram (also kilogramme) is the unit of mass in the International System of Units (SI), having the unit symbol kg. It is a widely used measure in science, engineering and commerce worldwide, and is often simply called a kilo colloquially ...
of KCl yields 16350 becquerel
The becquerel (; symbol: Bq) is the unit of radioactivity in the International System of Units (SI). One becquerel is defined as the activity of a quantity of radioactive material in which one nucleus decays per second. For applications relatin ...
s of radiation
In physics, radiation is the emission or transmission of energy in the form of waves or particles through space or through a material medium. This includes:
* ''electromagnetic radiation'', such as radio waves, microwaves, infrared, visi ...
, consisting of 89.28% beta and 10.72% gamma
Gamma (uppercase , lowercase ; ''gámma'') is the third letter of the Greek alphabet. In the system of Greek numerals it has a value of 3. In Ancient Greek, the letter gamma represented a voiced velar stop . In Modern Greek, this letter re ...
, with 1.46083 MeV. In order to use off-the-shelf materials, it needs to be crystallized sequentially, using controlled temperature, in order to extract KCl, which is the subject of ongoing research. It also emits a relatively low level of 511 keV gamma rays from positron annihilation, which can be used to calibrate medical scanners.
Potassium chloride is used in some de-icing
Deicing is the process of removing snow, ice or frost from a surface. Anti-icing is the application of chemicals that not only deice but also remain on a surface and continue to delay the reformation of ice for a certain period of time, or prev ...
products designed to be safer for pets and plants, though these are inferior in melting quality to calcium chloride
Calcium chloride is an inorganic compound, a salt with the chemical formula . It is a white crystalline solid at room temperature, and it is highly soluble in water. It can be created by neutralising hydrochloric acid with calcium hydroxide.
Ca ...
owest usable temperature v. It is also used in various brands of bottled water
Bottled water is drinking water (e.g., well water, distilled water, mineral water, or spring water) packaged in plastic or glass water bottles. Bottled water may be carbonated or not. Sizes range from small single serving bottles to lar ...
.
Potassium chloride was once used as a fire extinguishing agent, and in portable and wheeled fire extinguisher
A fire extinguisher is a handheld active fire protection device usually filled with a dry or wet chemical used to extinguish or control small fires, often in emergencies. It is not intended for use on an out-of-control fire, such as one which ha ...
s. Known as Super-K dry chemical, it was more effective than sodium bicarbonate-based dry chemicals and was compatible with protein foam. This agent fell out of favor with the introduction of potassium bicarbonate
Potassium bicarbonate (IUPAC name: potassium hydrogencarbonate, also known as potassium acid carbonate) is the inorganic compound with the chemical formula KHCO3. It is a white solid.
Production and reactivity
It is manufactured by treating an ...
( Purple-K) dry chemical in the late 1960s, which was much less corrosive
A corrosive substance is one that will damage or destroy other substances with which it comes into contact by means of a chemical reaction.
Etymology
The word ''corrosive'' is derived from the Latin verb ''corrodere'', which means ''to gnaw'', ...
, as well as more effective. It is rated for B and C fires.
Along with sodium chloride
Sodium chloride , commonly known as salt (although sea salt also contains other chemical salts), is an ionic compound with the chemical formula NaCl, representing a 1:1 ratio of sodium and chloride ions. With molar masses of 22.99 and 35.45 g ...
and lithium chloride
Lithium chloride is a chemical compound with the formula Li Cl. The salt is a typical ionic compound (with certain covalent characteristics), although the small size of the Li+ ion gives rise to properties not seen for other alkali metal chlor ...
, potassium chloride is used as a flux
Flux describes any effect that appears to pass or travel (whether it actually moves or not) through a surface or substance. Flux is a concept in applied mathematics and vector calculus which has many applications to physics. For transport ph ...
for the gas welding
Principle of burn cutting
Oxy-fuel welding (commonly called oxyacetylene welding, oxy welding, or gas welding in the United States) and oxy-fuel cutting are processes that use fuel gases (or liquid fuels such as gasoline or petrol, diesel, ...
of aluminium
Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. I ...
.
Potassium chloride is also an optical crystal with a wide transmission range from 210 nm to 20 µm. While cheap, KCl crystals are hygroscopic
Hygroscopy is the phenomenon of attracting and holding water molecules via either absorption or adsorption from the surrounding environment, which is usually at normal or room temperature. If water molecules become suspended among the substan ...
. 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 for infrared
Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from around ...
optics
Optics is the branch of physics that studies the behaviour and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behaviour of visible, ultraviole ...
, it has been entirely replaced by much tougher crystals such as zinc selenide
Zinc selenide (ZnSe) is a light-yellow, solid compound comprising zinc (Zn) and selenium (Se). It is an intrinsic semiconductor with a band gap of about 2.70 eV at . ZnSe rarely occurs in nature, and is found in the mineral that was named af ...
.
Potassium chloride is used as a scotophor with designation P10 in dark-trace CRTs, e.g. in the Skiatron.
Toxicity
The typical amounts of potassium chloride found in the diet appear to be generally safe. In larger quantities, however, potassium chloride is toxic. The of orally ingested potassium chloride is approximately 2.5 g/kg, or for a body mass of . In comparison, the of sodium chloride
Sodium chloride , commonly known as salt (although sea salt also contains other chemical salts), is an ionic compound with the chemical formula NaCl, representing a 1:1 ratio of sodium and chloride ions. With molar masses of 22.99 and 35.45 g ...
(table salt) is 3.75 g/kg.
Intravenously, the 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) by the proportion by mass of potassium ions in potassium chloride (about 0.52445 mg K+/mg KCl).
Chemical properties
Solubility
KCl is soluble in a variety of polar solvents.
Solutions of KCl are common standards, for example for calibration
In measurement technology and metrology, calibration is the comparison of measurement values delivered by a device under test with those of a calibration standard of known accuracy. Such a standard could be another measurement device of know ...
of the electrical conductivity
Electrical resistivity (also called specific electrical resistance or volume resistivity) is a fundamental property of a material that measures how strongly it resists electric current. A low resistivity indicates a material that readily allow ...
of (ionic) solutions, since KCl solutions are stable, allowing for reproducible measurements. In aqueous solution, it is essentially fully ionized into solvated and ions.
Redox and the conversion to potassium metal
Although potassium is more electropositive
Electronegativity, symbolized as , is the tendency for an atom of a given chemical element to attract shared electrons (or electron density) when forming a chemical bond. An atom's electronegativity is affected by both its atomic number and the d ...
than sodium
Sodium is a chemical element with the symbol Na (from Latin ''natrium'') and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 of the periodic table. Its only stable iso ...
, 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
Le Chatelier's principle (pronounced or ), also called Chatelier's principle (or the Equilibrium Law), is a principle of chemistry used to predict the effect of a change in conditions on chemical equilibria. The principle is named after French c ...
):
:KCl_ + Na_ <=> NaCl_ + K_
This method is the main method for producing metallic potassium. Electrolysis
In chemistry and manufacturing, electrolysis is a technique that uses direct electric current (DC) to drive an otherwise non-spontaneous chemical reaction. Electrolysis is commercially important as a stage in the separation of elements from n ...
(used for sodium) fails because of the high solubility of potassium in molten KCl.
Physical properties
The crystal structure of potassium chloride is like that of NaCl. It adopts a face-centered cubic structure. Its lattice
Lattice may refer to:
Arts and design
* Latticework, an ornamental criss-crossed framework, an arrangement of crossing laths or other thin strips of material
* Lattice (music), an organized grid model of pitch ratios
* Lattice (pastry), an orna ...
constant is roughly 6.3 Ã…. Crystals cleave easily in three directions.
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)
*d''N''/d''T'' (expansion coefficient)= −33.2×10−6/°C
*d''L''/d''T'' (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
A flame (from Latin ''flamma'') is the visible, gaseous part of a fire. It is caused by a highly exothermic chemical reaction taking place in a thin zone. When flames are hot enough to have ionized gaseous components of sufficient density they ...
.
Production
Potassium chloride is extracted from minerals sylvite, carnallite
Carnallite (also carnalite) is an evaporite mineral, a hydrated potassium magnesium chloride with formula KMgCl3·6(H2O). It is variably colored yellow to white, reddish, and sometimes colorless or blue. It is usually massive to fibrous with rare ...
, and potash
Potash () includes various mined and manufactured salts that contain potassium in water-soluble form. . It is also extracted from salt water
Saline water (more commonly known as salt water) is water that contains a high concentration of dissolved salts (mainly sodium chloride). On the United States Geological Survey (USGS) salinity scale, saline water is saltier than brackish water, ...
and can be manufactured by crystallization from solution, flotation or electrostatic
Electrostatics is a branch of physics that studies electric charges at rest (static electricity).
Since classical times, it has been known that some materials, such as amber, attract lightweight particles after rubbing. The Greek word for amber ...
separation from suitable minerals. It is a by-product of the production of nitric acid
Nitric acid is the inorganic compound with the formula . It is a highly corrosive mineral acid. The compound is colorless, but older samples tend to be yellow cast due to decomposition into oxides of nitrogen. Most commercially available nitri ...
from potassium nitrate
Potassium nitrate is a chemical compound with the chemical formula . This alkali metal nitrate salt is also known as Indian saltpetre (large deposits of which were historically mined in India). It is an ionic salt of potassium ions K+ and nitrat ...
and hydrochloric acid
Hydrochloric acid, also known as muriatic acid, is an aqueous solution of hydrogen chloride. It is a colorless solution with a distinctive pungent smell. It is classified as a strong acid
Acid strength is the tendency of an acid, symbol ...
.
The vast majority of potassium chloride is produced as agricultural and industrial grade potash in Saskatchewan, Canada
Saskatchewan ( ; ) is a province in western Canada, bordered on the west by Alberta, on the north by the Northwest Territories, on the east by Manitoba, to the northeast by Nunavut, and on the south by the U.S. states of Montana and North Dak ...
, as well as Russia and Belarus. Saskatchewan alone accounted for over 25% of the world's potash production in 2017.
Laboratory methods
Potassium chloride is inexpensively available and is rarely prepared intentionally in the laboratory. It can be generated by treating potassium hydroxide
Potassium hydroxide is an inorganic compound with the formula K OH, and is commonly called caustic potash.
Along with sodium hydroxide (NaOH), KOH is a prototypical strong base. It has many industrial and niche applications, most of which exp ...
(or other potassium bases) with hydrochloric acid
Hydrochloric acid, also known as muriatic acid, is an aqueous solution of hydrogen chloride. It is a colorless solution with a distinctive pungent smell. It is classified as a strong acid
Acid strength is the tendency of an acid, symbol ...
:
:KOH + HCl -> KCl + H2O
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 + Cl2 -> 2 KCl
References
Further reading
*
*
External links
*
{{Authority control
Alkali metal chlorides
Chlorides
Dietary minerals
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Inorganic fertilizers
Lethal injection components
Metal halides
Potash
Potassium compounds
World Health Organization essential medicines
E-number additives
Rock salt crystal structure