7440-09-7 Usage
Description
Potassium, with atomic number 19 and the chemical symbol K, is a silvery-white metallic element derived from its Latin name kalium. It occurs naturally only in the form of its ion (K+) due to its violent reaction with water. Potassium ions are essential for both human bodies and plants, and the major use of K+ can be found in fertilizers containing various potassium salts.
Uses
Used in Photography:
Potassium is used as a component in the production of photographic compounds, which were widely used in the 19th century.
Used in Chemical Synthesis:
Potassium is used as a reagent in the synthesis of inorganic potassium compounds and organic syntheses involving condensation, dehalogenation, reduction, and polymerization reactions.
Used in Heat Transfer:
Potassium, when alloyed with sodium (NaK), is used as a heat transfer medium in cooling nuclear reactors.
Used in Geological Dating:
The radioactive decay of 40K to 40Ar is used as a tool for geological dating.
Used in Chemical and Industrial Laboratories:
Potassium is used as an important reagent to form many compounds in chemical and industrial laboratories.
Used in Soap Manufacturing:
Potassium is used in the manufacture of both hard and soft soaps.
Used in Bleaching and Caustic Chemicals:
Potassium is used as a bleaching agent and in applications where a highly caustic chemical is required.
Used in Human Diet and Health:
Potassium is an essential trace element required for a healthy diet and is found in many foods, such as bananas.
Used in Reactive Potassium Salts Production:
Potassium is used in the manufacture of many reactive potassium salts for various applications.
Potassium and health
Potassium in its ionic form, K+, is the most abundant positive ion in human and animal cells. As an electrolytic solution, K+ ions are pumped through the blood to all vital organs. Potassium's importance to the physiological system cannot be overstated: It plays a crucial role in electrical pulse transmission along nerve fibers; protein synthesis; acid-base balance; and formation of collagen, elastin, and muscle.
Potassium is highly soluble in water and regulates flow across semipermeable membranes like cell walls. It is this feature that makes a deficiency or an excess of potassium hazardous to health. Either extreme can have undesirable and even disastrous consequences.
Production
Potassium can be produced by several methods that may be classified under three distinct types: (1) electrolysis, (2) chemical reduction, and (3) thermal decomposition.
Electrolysis processes have been known since Davy first isolated the metal in 1807. Electrolysis, however, suffers from certain disadvantages. A major problem involves miscibility of the metal with its fused salts. Because of this molten potassium chloride, unlike sodium chloride, cannot be used to produce the metal. Fused mixtures of potassium hydroxide and potassium carbonate or chloride have been used as electrolytes with limited success. Chemical reduction processes are employed nowadays in commercial, as well as, laboratory preparation of potassium. In one such process, molten potassium chloride is reduced with sodium at 760 to 880oC and the free metal is separated by fractionation:
KCl + Na → K + NaCl
Potassium is obtained at over 99.5% purity. The metal, alternatively, may be alloyed with sodium for further applications.
Reduction of potassium fluoride with calcium carbide at 1,000 to 1,100oC (Greisheim process) is an effective production method (Greer, J.S., Madaus, J.H and J.W. Mausteller. 1982. In Kirk-Othmer Encyclopedia of Chemical Technology, 3rd ed. p. 914, New York: Wiley Interscience):
2KF + CaC2 → CaF2 + 2C + 2K
Some other chemical reduction methods that may be applied for laboratory generation of small quantities of potassium from its salts at high temperatures require a suitable reducing agent such as carbon, calcium, or calcium carbide:
K2CO3 + 2C → 3CO +2K
2KCl + Ca → CaCl2 + 2K
2KCl + CaC2 → CaCl2 + 2C + 2K
2K2CO3 + +3Si + 3CaO → 4K + 2C + 3CaSiO3
2K2SiO3 + Si + 3 CaO → 4K + 3CaSiO3
Potassium can be produced by thermal decomposition of potassium azide:
2KN3 → 2K + 3N2
High purity metal may be produced by distillation of technical grade metal. Potassium (technical grade) may be packed under nitrogen. Argon should be used for packing high purity metal. Metal is shipped in stainless steel or carbon containers. In small quantities potassium is transported in glass or metal ampules.
Reactions
Potassium reacts with oxygen or air forming three oxides: potassium monoxide, K2O; potassium peroxide, K2O2; and potassium superoxide, KO2. The nature of the product depends on oxygen supply. In limited supply of oxygen potassium monoxide is formed, while in excess oxygen, superoxide is obtained:
4K + O2 → 2K2O
2K + O2 → K2O2
K + O2 → KO2
Potassium reacts violently with water, forming potassium hydroxide:
2K + 2H2O → 2KOH + H2
Potassium reacts with hydrogen at about 350oC to form potassium hydride:
2K + H2 → 2KH
Reactions with halogens, fluorine, chlorine and bromine occur with explosive violence. Thus, in contact with liquid bromine it explodes forming potassium bromide:
2K + Br2 → 2KBr
Potassium ignites in iodine vapor forming potassium iodide.
Violent reactions can occur with many metal halides. For example, with zinc halides or iron halides, single replacement reactions take place. Such potassium-metal halide mixtures can react violently when subjected to mechanical shock.
At ordinary temperatures, potassium does not combine with nitrogen but with an electric charge, potassium azide is formed.
Reaction with carbon (graphite) at above 400oC produces a series of carbides, such as KC4, KC8, and KC24. With carbon monoxide, an unstable explosive carbonyl forms:
K + CO → KCO
Potassium reduces carbon dioxide to carbon, carbon monoxide and potassium carbonate:
6K + 5CO2 → CO + C + 3K2CO3
Potassium reacts with ammonia gas to form potassium amide with liberation of hydrogen:
2K + 2NH3 → 2KNH2 + H2
Reactions with phosphorus, arsenic and antimony form phosphide, arsenide, and antimonide of potassium, respectively:
K + As → K3As
Reaction with sulfur forms three sulfides. When reactants are in molten state, the product is K2S, but in liquid ammonia K2S2 and KS2 are the main products.
Potassium reacts explosively with sulfuric acid, forming potassium sulfate with evolution of hydrogen:
K + H2SO4 → K2SO4 + H2
Potassium liberates hydrogen from ethanol forming potassium ethoxide:
2K + 2C2H5OH → 2C2H5OK + H2
Reaction with potassium nitrate yields potassium monoxide and nitrogen:
10K + 2KNO3 → 6K2O + N2
Hazard
Potassium metal can be dangerous to handle if proper precautions are not taken. Many of its reactions at ordinary temperatures can proceed to explosive violence (see Reactions). Also, it liberates flammable hydrogen gas when combined with water, acids, and alcohols.
Hazard
Elemental potassium as a metal is not found in its pure form in nature, but is derived fromits numerous compounds. The metal is very dangerous to handle. It can ignite while you areholding it with your hands or as you cut it. The metal must be stored in an inert gas atmosphereor in oil. Potassium fires cannot be extinguished with water—it only makes matters worsebecause it results in the formation of potassium hydroxide and hydrogen gas with enough heatto ignite the hydrogen. Dry chemicals such as soda ash, graphite, or dry sand can be used.A particular hazard, which has been with humans since the beginning of time, is theradioactive isotope potassium-40 (K-40). Less than 1% of all potassium atoms on Earth arein the form of this radioactive isotope. It has a half-life of 1.25 billion years. Its decay process ends with the formation of the noble gas argon, which can then be analyzed to determine theage of rocks. This system (K-40 → argon) has been used to establish that the oldest rocks onEarth were formed about 3.8 billion years ago. Every living thing needs some potassium inits diet, including humans, who cannot escape this source of radiation, given that the humanbody cannot distinguish the radioactive potassium from the nonradioactive form. Along withcosmic rays and other naturally radioactive elements in the Earth’s crust, potassium-40 contributesto the normal lifetime accumulation of radiation. It makes up almost one-fourth ofthe total radiation the human body receives during a normal life span.
Isotopes
A total of 18 isotopes of potassium have been discovered so far. Just two ofthem are stable: K-39 makes up 93.2581% of potassium found in the Earth’s crust, andK-41 makes up 6.7301% of the remainder of potassium found on Earth. All the other16 potassium isotopes are unstable and radioactive with relatively short half-lives, and asthey decay, they produce beta particles. The exception is K-40, which has a half-life of1.25×109 years.
Origin of Name
Its symbol “K” is derived from the Latin word for alkali, kalium, but it is
commonly called “potash” in English.
Characteristics
Because its outer valence electrons are at a greater distance from its nuclei, potassium ismore reactive than sodium or lithium. Even so, potassium and sodium are very similar in theirchemical reactions. Due to potassium’s high reactivity, it combines with many elements, particularly nonmetals. Like the other alkali metals in group 1, potassium is highly alkaline (caustic) with a relatively high pH value. When given the flame test, it produces a violet color.
History
Discovered in 1807 by Davy, who obtained
it from caustic potash (KOH); this was the first metal isolated
by electrolysis. The metal is the seventh most abundant and
makes up about 2.4% by weight of the Earth’s crust. Most potassium
minerals are insoluble and the metal is obtained from
them only with great difficulty. Certain minerals, however,
such as sylvite, carnallite, langbeinite, and polyhalite are found
in ancient lake and sea beds and form rather extensive deposits
from which potassium and its salts can readily be obtained. Potash is mined in Germany, New Mexico, California, Utah,
and elsewhere. Large deposits of potash, found at a depth of
some 1000 m in Saskatchewan, promise to be important in
coming years. Potassium is also found in the ocean, but is
present only in relatively small amounts compared to sodium.
The greatest demand for potash has been in its use for fertilizers.
Potassium is an essential constituent for plant growth
and it is found in most soils. Potassium is never found free in
nature, but is obtained by electrolysis of the hydroxide, much
in the same manner as prepared by Davy. Thermal methods
also are commonly used to produce potassium (such as by reduction
of potassium compounds with CaC2, C, Si, or Na). It is
one of the most reactive and electropositive of metals. Except
for lithium, it is the lightest known metal. It is soft, easily cut
with a knife, and is silvery in appearance immediately after a
fresh surface is exposed. It rapidly oxidizes in air and should
be preserved in a mineral oil. As with other metals of the alkali
group, it decomposes in water with the evolution of hydrogen.
It catches fire spontaneously on water. Potassium and
its salts impart a violet color to flames. Twenty-one isotopes,
one of which is an isomer, of potassium are known. Ordinary
potassium is composed of three isotopes, one of which is 40K
(0.0117%), a radioactive isotope with a half-life of 1.26 × 109
years. The radioactivity presents no appreciable hazard. An
alloy of sodium and potassium (NaK) is used as a heat-transfer
medium. Many potassium salts are of utmost importance,
including the hydroxide, nitrate, carbonate, chloride, chlorate,
bromide, iodide, cyanide, sulfate, chromate, and dichromate.
Metallic potassium is available commercially for about $1200/
kg (98% purity) or $75/g (99.95% purity).
Production Methods
Potassium superoxide
(KO2) can create oxygen from water vapor (H2O) and carbon
dioxide (CO2) and is used in respiratory equipment and is
produced by burning potassium metal in dry air.
Preparation
Potassium metal is not produced commercially by a fused salt electrolysis of the chloride
—as is sodium—for several reasons: the metal is too soluble in the molten chloride to
separate and float on top of the bath; potassium metal vapors may also issue from the
molten bath, thus creating hazardous conditions; and potassium superoxide may form in the
cell and react explosively with potassium metal. Consequently, the established method of
preparing potassium metal commercially? involves the reduction of molten potassium
chloride by metallic sodium at elevated temperatures (850°C). Molten potassium chloride
is fed into the midpoint of a steel vessel provided with a fractionating tower packed with
stainless steel rings. Sodium is vaporized at the bottom and rises countercurrent to the
molten potassium chloride with which it reacts according to the equilibrium expression.
Although the left-hand side of the equation is favored thermodynamically, the escape of the
potassium vapors causes the reaction to proceed very efficiently to the right. The potassium
vapors are condensed and the product normally contains sodium metal as the only major
impurity up to about 1 % by weight. This product is sometimes purified by fractionating it in
a 38 ft high 316 stainless steel tower equipped with a reflux return reservoir. The condensate
is potassium metal of 99.99 % purity.
Air & Water Reactions
Reacts vigorously with oxygen. Reacts vigorously with water even at less than 100°C [Merck, 11th ed., 1989]. Water (caustic solution, H2) The oxidation of potassium in air is so rapid that the heat generated by the reaction melts and ignites the metal. This is particularly the case when pressure is applied at ordinary temperatures [Sidgwick 1. 1950]. Potassium burns in moist air at room temperature [Mellor 2:468. 1946-47]. The higher oxides of potassium, formed in air, react explosively with pure potassium, sodium, sodium-potassium alloys, and organic matter [Mellor 2, Supp. 3:1559. 1963].
Reactivity Profile
Boron trifluoride reacts with incandescence when heated with alkali metals or alkaline earth metals except magnesium [Merck 11th ed. 1989]. Maleic anhydride decomposes explosively in the presence of alkali metals . Sodium peroxide oxidizes antimony, arsenic, copper, potassium, tin, and zinc with incandescence . Alkali metal hydroxides, acids, anhydrous chlorides of iron, tin, and aluminum, pure oxides of iron and aluminum, and metallic potassium are some of the catalysts that may cause ethylene oxide to rearrange and polymerize, liberating heat . Explosions occur, although infrequently, from the combination of ethylene oxide and alcohols or mercaptans [Chem. Eng. News 20:1318. 1942]. A mixture of potassium and any of the following metallic halides produces a strong explosion on impact: aluminum chloride, aluminum fluoride, ammonium fluorocuprate, antimony tribromide, antimony trichloride, antimony triiodide, cadmium bromide, cadmium chloride, cadmium iodide, chromium tetrachloride, cupric bromide, cupric chloride, cuprous bromide cuprous chloride, cuprous iodide, manganese chloride, mercuric bromide, mercuric chloride, mercuric fluoride, mercuric iodide, mercurous chloride, nickel bromide, nickel chloride, nickel iodide, silicon tetrachloride, silver fluoride, stannic chloride, stannic iodide (with silver), stannous chloride, sulfur dibromide, thallous bromide, vanadium pentachloride, zinc bromide, zinc chloride, and zinc iodide [Mellor 2, Supp. 3:1571. 1963]. A mixture of potassium and any of the following compounds produces a weak explosion on impact: ammonium bromide, ammonium iodide, cadmium fluoride, chromium trifluoride, manganous bromide, manganous iodide, nickel fluoride, potassium chlorocuprate, silver chloride, silver iodide, strontium iodide, thallous chloride, and zinc fluoride [Mellor 2, Supp. 3:1571. 1963]. A mixture of potassium and any of the following compounds may explode on impact: boric acid, copper oxychloride, lead oxychloride, lead peroxide, lead sulfate, silver iodate, sodium iodate, and vanadium oxychloride [Mellor 2, Supp. 3:1571. 1963]. A mixture of potassium with any of the following compounds produces a very violent explosion on impact: boron tribromide, carbon tetrachloride, cobaltous bromide, cobaltous chloride, ferric bromide, ferric chloride, ferrous bromide, ferrous chloride, ferrous iodide, phosphorus pentachloride, phosphorus tribromide, and sulfur dichloride [Mellor 2, Supp. 3:1571. 1963]. Mixture of solid potassium and carbon dioxide(as dry ice) explodes when subjected to shock [Mellor 2, Supp. 3:1568. 1963]. Potassium and its alloys form explosive mixtures with chlorinated hydrocarbons [Chem. Eng. News 26:2604. 1948]. Ethylene oxide is dangerously reactive with metallic potassium [Chemical Safety Data Sheet SD-38:11. 1951]. Potassium in contact with the following oxides causes an explosive reaction: potassium ozonide, potassium peroxide, or potassium superoxide [Mellor 2, Supp. 3:1577. 1963].
Health Hazard
Potassium reacts with the moisture on skin and other tissues to form highly corrosive potassium hydroxide. Contact of metallic potassium with the skin, eyes, or mucous membranes causes severe burns; thermal burns may also occur due to ignition of the metal and liberated hydrogen.
Flammability and Explosibility
Potassium metal may ignite spontaneously on contact with air at room temperature.
Potassium reacts explosively with water to form potassium hydroxide; the heat
liberated generally ignites the hydrogen formed and can initiate the combustion of
potassium metal itself. Potassium fires must be extinguished with a class D dry
chemical extinguisher or by the use of sand, ground limestone, dry clay or graphite,
or "Met-L-X?" type solids. Water or CO2, extinguishers must never be used on
potassium fires.
Safety Profile
The toxicity of
potassium compounds is almost always that
of the anion, not of potassium. A dangerous
fire hazard. Metallic potassium reacts with
moisture to form potassium hydroxide and
hydrogen. The reaction evolves much heat,
causing the potassium to melt and spatter.
The reaction also ignites the hydrogen,
which burns, or if there is any confinement, may explode. It can ignite spontaneously in
moist air. Store under mineral oil. Potassium
metal wdl form the peroxide (K2O2) and the
superoxide (KO3 or K2O4) at room
temperature even when stored under
mineral oil. These oxides can explode on
contact with organic materials. Metal that
has oxidized on storage under oil may
explode violently when handled or cut.
Oxide-coated potassium should be
destroyed by burning.
Danger: burning potassium is difficult to
extinguish; dry powdered soda ash or
graphte or special mixtures of dry chemical
are recommended.
A violent explosion hazard with the
following materials under required
conditions of temperature, pressure, and
state of division: acetylene, air, moist air,
alcohols (e.g., n-propanol through n-octanol,
benzyl alcohol, cyclohexanol), AlBr3,
ammonium nitrate + ammonium sulfate,
ammonium chlorocuprate, NHdi, NH41,
antimony halides, arsenic hahdes, AsH3 +
NH3, Bi203, boric acid, BBr3, carbon
disulfide (impact-sensitive), solid carbon
dioxide, carbon monoxide, chlorinated
hydrocarbons (e.g., chloroethane,
dichloroethane, dchloromethane,
trichloroethane, chloroform, pentachloro-
ethane, carbon tetrachloride, tetrachloro-
ethane), halocarbons (e.g., bromoform,
dbromomethane, diiodomethane) , iodme
(impact-sensitive), interhalogens (e.g.,
chlorine trifluoride, iodine bromide, iodine
chloride, iodine pentafluoride, iodme
trichloride), ClO, CrO3, Cu2OCl2, CuO,
ethylene oxide, fluorine, graphite, graphte +
air, graphite + K2O2, hydrogen iodide,
H2O2, hydrogen chloride, hydrazine,
Pb2OCl2, PbO2, PbSO4, maleic anhydride,
metal halides (e.g., calcium bromide,
iron(Ⅲ) bromide, iron(Ⅲ) chloride, iron(Ⅱ)
chloride, iron(Ⅱ) bromide, iron(Ⅱ) iodide,
cobalt(Ⅱ) chloride, chromium tetrachloride,
silver fluoride, mercury(Ⅱ) bromide,
mercury(Ⅱ) chloride, mercury(Ⅱ) fluoride,
mercury(Ⅱ) iodide, copper0 chloride,copper(Ⅰ) iodde, copper(Ⅱ) bromide,
copper(Ⅱ) chloride, ammonium
tetrachlorocuprate, zinc chlorides, bromides,
or ioddes, cadmium chlorides, bromides or
iodides, aluminum fluorides, chlorides, or
bromides, thalliump) bromide, tin chlorides,
tin iodide, arsenic trichloride, arsenic
triiodde, antimony tribromides, trichlorides
or triiodides, bismuth tribromides,
trichlorides, or triioddes, vanadiumo
chloride, manganese(Ⅰ) chloride, nickel
bromide, chloride, or iodide), metal oxides
(e.g., lead peroxide, mercury(Ⅰ) oxide,
MoO3, nitric acid, nitrogen-containing
explosives (e.g., ammonium nitrate, picric
acid, nitrobenzene), nonmetal halides (e.g.,
diselenium dichloride, seleninyl chloride,
seleninyl bromide, sulfur dichloride, sulfur
dibromide, phosphorus tribromide,
phosphorus trichloride, phosgene, disulfur
dichloride), nonmetal oxides (e.g., dichlorine
oxide, dinitrogen tetraoxide, dinitrogen
pentaoxide, NO2, P2O5), oxalyl dibromide,
oxalyl dichloride, P2NF, peroxides, COCl2,
PH3 + NH3, phosphorus, PCl5, PBr3,
potassium chlorocuprate, potassium oxides
(e.g., KO3, K2O2, KO2), selenium, SeOCl2,
SiCl4, AglO3, NalO3, NH3 + NaNO2,
Na2O2, SnI4 + S, SnO2, S, sulfuric acid,
tellurium, thiophosphoryl fluoride, VOCl2,
water.
Other hazardous reactions may occur
with carbon (e.g., soot, graphte, activated
charcoal), dimethyl sulfoxide, ethylene
oxide, chlorine, bromine vapor, hydrogen
bromide, potassium iodide + magnesium
bromide, chloride or iodide, maleic
anhydride, mercury, copper(Ⅱ) oxide,
mercury(Ⅱ) oxide, tin(Ⅳ) oxide,
molybdenum(Ⅲ) oxide, bismuth trioxide,
phosphorus trichloride, sulfur dioxide,
chromium trioxide.
toxic fumes of K2O.
When heated to decomposition it emits
Potential Exposure
Used as a reagent and in sodiumpotassium alloys which are used as high-temperature heat transfer media.
Environmental Fate
Potassium metal in the environment will react with air,
oxidizing the exposed surfaces, and reacts violently with water,
yielding potassium hydroxide and hydrogen gas, which reacts
with oxygen in air, producing flame.
storage
Safety glasses,
impermeable gloves, and a fire-retardant laboratory coat should be worn at all times
when working with potassium, and the metal should be handled under the surface of
an inert liquid such as mineral oil, xylene, or toluene. Potassium should be used only
in areas free of ignition sources and should be stored under mineral oil in tightly
sealed metal containers under an inert gas such as argon. Potassium metal that has
formed a yellow oxide coating should be disposed of immediately; do not attempt to
cut such samples with a knife since the oxide coating may be explosive.
Shipping
UN2257Potassium, Hazard Class: 4.3; Labels: 4.3-Dangerous when wet material. UN1420 Potassium, metal alloys and metal alloys, liquid, Hazard Class: 4.3; Labels: 4.3-Dangerous when wet material. UN3089 Metal powder, flammable, n.o.s. Hazard Class: 4.2; Labels: 4.2-Spontaneously combustible material.
Toxicity evaluation
Potassium is a cofactor and activates a large variety of enzymes,
including glycerol dehydrogenase, pyruvate kinase, L-threonine
dehydrase, and ATPase. Its acute toxicity is primarily due to its
action as an electrolyte. Excessive or diminished potassium
levels can disrupt membrane excitability and influence muscle
cell contractility and neuronal excitability.
Incompatibilities
Air contact causes spontaneous ignition. Violent reaction with water, forming heat, spattering, corrosive potassium hydroxide and explosive hydrogen. The heat from the reaction can ignite the hydrogen that is generated. A powerful reducing agent. Violent reaction with oxidizers, organic materials; carbon dioxide; heavy metal compounds; carbon tetrachloride; halogenated hydrocarbons; easily oxidized materials; and many other substances. Store under nitrogen, mineral oil, or kerosene. Oxidizes and forms unstable peroxides under storage conditions. Potassium metal containing an oxide coating is an extremely dangerous explosion hazard and should be removed by an expert and destroyed.
Waste Disposal
Excess potassium and waste material containing this substance should be placed in an appropriate container
under an inert atmosphere, clearly labeled, and handled according to your institution's waste disposal
guidelines. Experienced personnel can destroy small scraps of potassium by carefully adding t-butanol or nbutanol
to a beaker containing the metal scraps covered in an inert solvent such as xylene or toluene.
Check Digit Verification of cas no
The CAS Registry Mumber 7440-09-7 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 7,4,4 and 0 respectively; the second part has 2 digits, 0 and 9 respectively.
Calculate Digit Verification of CAS Registry Number 7440-09:
(6*7)+(5*4)+(4*4)+(3*0)+(2*0)+(1*9)=87
87 % 10 = 7
So 7440-09-7 is a valid CAS Registry Number.
InChI:InChI=1/K
This product is a nationally controlled contraband, and the Lookchem platform doesn't provide relevant sales information.
