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Molecular Formula
MDL Number
Molecular Weight
MOL File

Chemical Properties

K. Metallic element of atomic number 19, group IA of the periodic table, an alkali metal, aw 39.098, valence of 1. Potassium-40 is a naturally occurring radioactive isotope. There are also two stable isotopes. The synthetic isotope, potassium-42, is used
Potassium is a soft silvery metal
soft silvery metal, tarnishing upon exposure to air.
770 °C(lit.)

770 °C
1.98 g/mL at 25 °C(lit.)

vapor pressure 
0.09 mm Hg ( 260 °C)

refractive index 
n20/D 1.334

storage temp. 

H2O: soluble


Stable. Moisture and air-sensitive. Spontaneously combustible through the generation and ignition of hydrogen. Reacts violently with water and acids, alcohols, carbon monoxide. Store under oil.
Water Solubility 
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).
Some of the most common compounds in 19th century photography were made with this silvery metallic element discovered by Sir Humphrey Davy in 1807. There is not enough room in this work to list all of these compounds, but the following represent a reasonable sampling.
CAS DataBase Reference
7440-09-7(CAS DataBase Reference)
NIST Chemistry Reference
EPA Substance Registry System
7440-09-7(EPA Substance)

Safety Data

Hazard Codes 
Risk Statements 
R14/15:Reacts violently with water, liberating extremely flammable gases .
R34:Causes burns.
Safety Statements 
S8:Keep container dry .
S43:In case of fire, use ... (indicate in the space the precise type of fire-fighting equipment. If water increases the risk add-Never use water) .
S45:In case of accident or if you feel unwell, seek medical advice immediately (show label where possible) .
UN 2257 4.3/PG 1

WGK Germany 


HS Code 
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
Hazardous Substances Data
7440-09-7(Hazardous Substances Data)

Raw materials And Preparation Products

Hazard Information

General Description
POTASSIUM, METAL ALLOYS(7440-09-7) is potassium mixed with some other metal, usually sodium. POTASSIUM, METAL ALLOYS(7440-09-7) is a liquid under normal conditions. POTASSIUM, METAL ALLOYS(7440-09-7) reacts vigorously with water to form potassium hydroxide, a corrosive material and hydrogen, a flammable gas. The heat from this reaction may be sufficient to ignite the hydrogen. Potassium alloy may ignite spontaneously in contact with air. Once ignited, potassium burns quite violently. POTASSIUM, METAL ALLOYS(7440-09-7) is used as a heat exchange fluid.
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].
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].
Dangerous fire risk, reacts with moisture to form potassium hydroxide and hydrogen. The reac- tion evolves much heat, causing the potassium to melt and spatter. It also ignites the hydrogen. Burn- ing potassium is difficult to extinguish; dry pow- dered soda ash or graphite or a special mixture of dry chemicals is recommended. It can ignite spon- taneously in moist air. Moderate explosion risk by chemical reaction. Potassium metal will form the peroxide and the superoxide at room temperature even when stored under mineral oil; may explode violently when handled or cut. Oxide-coated potas- sium should be destroyed by burning. Store in inert atmospheres, such as argon or nitrogen, under liquids that are oxygen free, such as toluene or kerosene, or in glass capsules that have been filled under vacuum or inert atmosphere.
Health Hazard
Inhalation or contact with vapors, substance or decomposition products may cause severe injury or death. May produce corrosive solutions on contact with water. Fire will produce irritating, corrosive and/or toxic gases. Runoff from fire control may cause pollution.
Potential Exposure
Used as a reagent and in sodiumpotassium alloys which are used as high-temperature heat transfer media.
First aid
Eye Contact: Immediately remove any contact lenses and flush with large amounts of water. Continue without stopping for at least 30 minutes, occasionally lifting upper and lower lids. Seek medical attention immediately.
Skin Contact: Quickly remove contaminated clothing. Immediately wash area with large amounts of water. Seek medical attention immediately
Breathing: Remove the person from exposure. Begin (using universal precautions, including resuscitation mask) if breathing has stopped and CPR if heart action has stopped. Transfer promptly to a medical facility. Medical observation is recommended for 2448 hours after breathing overexposure, as pulmonary edema may be delayed.
Fire Hazard
Produce flammable gases on contact with water. May ignite on contact with water or moist air. Some react vigorously or explosively on contact with water. May be ignited by heat, sparks or flames. May re-ignite after fire is extinguished. Some are transported in highly flammable liquids. Runoff may create fire or explosion hazard.
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.
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.

Material Safety Data Sheet(MSDS)

msds information

Questions And Answer

Potassium was first isolated as a free metal in 1807 by Sir Humphry Davy. It was the first alkali metal to be discovered, produced by electrolysis of potassium carbonate (potash). The element was earlier called Kalium, derived from the Arabic word qili, meaning grass wort, the ash of which was a source of potash. The element derived its symbol K from Kalium. The English name potassium came from potash (pot ash), the carbonate salt of the metal.
Potassium is distributed widely in nature. The metal is too reactive to occur in native elemental form. It is the seventh most abundant element on earth, constituting 2.40% by weight of the earth’s crust. It is abundantly present in sea water. Oceans contain 0.07% (wt to volume) potassium chloride.
Potassium occurs in many igneous rocks, such as, feldspar (potassium aluminum silicate), KAlSi3O8 (leucite) and mica, KH2Al3(SiO4)3. Disintegration of these rocks adds potassium to soil and water. Deposits of potassium chloride are found in practically all salt beds, associated with sodium chloride. Some important potassium minerals are leucite, KAlSi2O6; glauconite (a complex silicoaluminate structure of varying compositions); sylvite, KCl; carnallite, KCl•MgCl2•6H2O; langbeinite, K2SO4•2MgSO4; and polyhalite, K2SO4•MgSO4•2CaSO4•2H2O.
Potassium, along with nitrogen and phosphorus, is an essential element needed for plant growth. In plants, it occurs mostly as K+ ion in cell juice. It is found in fruit or seed. Deficiency can cause curling leaves, yellow or brown coloration of leaves, weak stalk and diminished root growth. Potassium deficiency has been associated with several common animal ailments. Potassium is in extracellular fluid in animals at lower concentrations than sodium.
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.
Physical Properties
Silvery metal; body-centered cubic structure; imparts crimson-red color to flame; density 0.862g/cm3 at 20ºC; melts at 63.25ºC; density of liquid potassium at 100ºC is 0.819 g/cm3 and 0.771g/cm3 at 300ºC; vaporizes at 760ºC; vapor pressure 123 torr at 587ºC; electrical resistivity 6.1 microhm-cm at 0ºC and 15.31 microhm-cm at 100ºC; viscosity 0.25 centipoise at 250ºC; surface tension 86 dynes/cm at 100ºC; thermal neutron absorption cross section 2.07 barns; reacts violently with water and acids; reacts with alcohol; dissolves in liquid ammonia and mercury.
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.
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
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.

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