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Potassium carbonate

Basic information Description Outline Reference quality standards Content Analysis Solubility of potassium carbonate in water Toxicity Limited use Chemical Properties Production method Uses References Safety Related Supplier

Potassium carbonate Basic information

Product Name:
Potassium carbonate
Mol File:

Potassium carbonate Chemical Properties

Melting point:
891 °C(lit.)
Boiling point:
decomposes [STR93]
2.43 g/mL at 25 °C
storage temp. 
Store at RT.
H2O: 1 M at 20 °C, clear, colorless
Specific Gravity
11.5-12.5 (50g/l, H2O, 20℃)
Water Solubility 
1120 g/L (20 ºC)
λ: 260 nm Amax: 0.03
λ: 280 nm Amax: 0.02
Stable. Incompatible with moisture, acids, magnesium bromine trifluoride and magnesium bromine trichloride.
CAS DataBase Reference
584-08-7(CAS DataBase Reference)
NIST Chemistry Reference
Dipotassium carbonate(584-08-7)
EPA Substance Registry System
Potassium carbonate (584-08-7)

Safety Information

Hazard Codes 
Risk Statements 
Safety Statements 
WGK Germany 
HS Code 
Hazardous Substances Data
584-08-7(Hazardous Substances Data)
LD50 orally in rats: 1.87 g/kg, H. F. Smyth et al., Am. Ind. Hyg. Assoc. J. 30, 470 (1969)



Potassium carbonate Usage And Synthesis


Potassium carbonate (molecular formula: K2CO3), also known as potash or pearl ash, appears as a white powder or as colorless solid crystal with salty taste and deliquescence. It can be dissolved in water to form a strongly alkaline solution. However, it is insoluble in organic solvents such as ethanol. It has wide applications. For example, it can be used as a drying agent, buffering agent and a source of potassium in laboratory. It can also be used for the manufacturing of fire extinguishers, soap, glass, and soften water. In addition, it is also used during the production of cocoa powder to balance pH. Moreover, it can be supplied to effervescent tablets which can conveniently provide potassium when there are low levels of potassium in the blood for patients caused by various kinds of factors. In industry, potassium carbonate is manufactured though first performing electrolysis of potassium chloride to generate potassium hydroxide, followed by reaction with carbon dioxide to derive the product. It is toxic upon eye contact, inhalation and ingestion. For rats, it has an oral LD50 being 1870 mg/kg. It has chronic effects on humans, causing damage to the mucous membranes, skin, and eyes.


Potassium carbonate (chemical formula: K2CO3), also known as potash; its appearance is colorless crystal or white granules and is easily soluble in water with its solution being strongly alkaline. Cool its saturated solution with generating glassy monoclinic crystalline hydrate 2K2CO3 • 3H2O separated. It has a density of 2.043. It will lose its crystal water at 100 ℃. It is insoluble in ethanol, acetone and ether. It has a strong hygroscopic effect and can absorb carbon dioxide and water upon exposure to air to be converted into potassium bicarbonate. It can be generated through the reaction between potassium hydroxide with carbon dioxide to give. You can also obtain it through the heating reaction between potassium chloride and magnesium carbonate, water and carbon dioxide under pressure or obtain it through the impregnation of tung seed ash and plant ash. It is mainly used as the raw material for synthesis of decarbonization gas, electronic tubes, glass, enamel, printing, welding, film developing, inorganic salts and kinescope glass shell. The impure potassium carbonate base is usually called base, Tong base or pearl grey and is one kind of early species of potash.
The above information is edited by the Chemicalbook of Dai Xiongfeng.

Reference quality standards

Item Premium grade First grade Qualified II type
Potassium carbonate (K2CO3) content ≥ 99.0% 98.5% 96.0% 99.0%
Chloride (KCl) content ≤ 0.01% 0.10% 0.20% 0.03%
Sulfur compounds (in K2SO4) content ≤0.01% 0.10% 0.15% 0.04%
Iron (Fe) content of ≤ 0.001% 0.003% 0.010% 0.001%
Water-insoluble content ≤ 0.02% 0.05% 0.10% 0.04%
Burning loss ≤ 0.60% 1.00% 1.00% 0.80%

Content Analysis

To a pre-weighed weighing bottle with a plug, accurately weigh 1 g of dried sample measured according to the "loss on drying" assay and dissolve it in 50ml water. After adding of 2 drops of methyl red test solution (TS-149), stir continuously and titrate with 1mol/L hydrochloric acid titration until the solution turns into light pink. Heating the solution to boiling and further cool it down, continue to titrate to boiling until a pale pink color doesn’t disappears any more. Each Ml of 1mol/L hydrochloric acid is equivalent of 69.1 mg of potassium carbonate (K2CO3)

Solubility of potassium carbonate in water

The maximum solubility per 100 g of water at different temperatures (℃):
107g/0 ℃; 109g/10 ℃; 111g/20 ℃; 114g/30 ℃;
117g/40 ℃; 126g/60 ℃; 139g/80 ℃; 156g/100 ℃.


ADI does not make special provision (FAO/WHO, 2001).
LD50: 18.70mg/kg (rat, oral).
GRAS (FDA, §184.1619, 2000);

Limited use

GB 2760-2001: pasta, beverages, processing aids; take the GMP as limit.
FAO/WHO (1984): Low times concentrated milk, sweetened condensed milk, dilute cream (2g/kg when being used alone; apply 3g/kg when being used together with other stabilizers, calculated based on anhydrous matter); milk powder, cream powder 5g/kg ( calculated based on anhydride); jams and jellies, orange peel jelly (to maintain the Ph value being at 2.8 to 3.5); infant formula (according to GMP); chocolate 50g/kg (calculated based on the incorporated part from cocoa beans, cocoa nibs, cocoa liquor, cocoa cakes, etc.); cocoa powder, sugar-containing cocoa powder, cocoa nibs, cocoa liquor and cocoa cake 5 g/kg (calculated from non-fat cocoa and K2CO3 meter; can be used for the manufacture of cocoa and chocolate products).

Chemical Properties

It belongs to monoclinic, and is white powder or granular crystal. It is easily soluble in water but insoluble in alcohol and ether.

Production method

The ion exchange method: dubbed 250 g/L solution and adding a small amount of potassium carbonate to remove calcium and magnesium ions. Ammonium bicarbonate solution is also prepared at a concentration 200 g/L in water. Pass the potassium chloride solution through a countercurrent into ion exchange column, to make the sodium resin R-Na become potassium type RK, wash off the chlorine ion within the gap of the soft resin; after finishing washing, put through the ammonium bicarbonate solution downstream into the resin exchange column, making the resin become ammonium type R-NH4 and obtain a mixed dilute solution of potassium bicarbonate and ammonium bicarbonate; go through evaporation once to decompose the ammonium bicarbonate; evaporate once again to decompose most of the potassium bicarbonate into potassium carbonate; the precipitated potassium chloride crystal after cooling was filtered and removed; further go through evaporation for three times to 54°C and filter to remove the compound salt of potassium and sodium. The solution was subject to carbonation to convert the potassium carbonate into potassium bicarbonate; further go through crystallization, separation, washing, calcination to obtain the finished product. Its reaction steps are as below:
R-Na + KCl → R-K + NaCl
R-K + NH4HCO3 → R-NH4 + KHCO3
2KHCO3 → K2CO3 + CO2 ↑+ H2O
Apply electrolysis to dissolve the potassium chloride to a concentration of 270~300 g/L with adding appropriate amount of potassium carbonate to remove the calcium and magnesium ions inside it. After the clarification of the solution, adjust to pH 8~10 with hydrochloric acid; perform electrolysis at the cell voltage of 2.8~3.5 V and the bath temperature of 60~70 ℃ to obtain the potassium hydroxide solution with a concentration of 10% to 15%; further go through evaporation and concentration to a 50% potassium hydroxide and cool down to 30~35 ℃; Recycle the precipitated potassium chloride for reuse. Dilute the concentrated alkali solution to about 44%, and perform pre-carbonization; when the concentration of potassium hydroxide reaches 30 g/L or less, filter to remove the precipitate of magnesium hydroxide and then go through concentration for removing sodium; then conduct the carbonization to obtain the crude potassium carbonate with further carbonation obtaining the potassium bicarbonate crystals; The crystals undergoes washing with water, centrifuge, calcination to obtain the refined product of potassium carbonate. Its reaction steps are as below:
2KCl + 2H2O [electrolysis] → 2KOH + Cl2 ↑ + H2 ↑
2KOH + CO2 → K2CO3 + H2O
K2CO3 + CO2 + H2O → 2KHCO3
2KHCO3 → K2CO3 + CO2 ↑ + H2O
The plant ash method mainly take advantage of various kinds of plant shell such as Kiriko shell, cotton seed hulls, tea and sunflower seed hulls for firing into plant ash. The plant ash is a mixture of potassium carbonate, potassium sulfate, and potassium chloride. They are separated by multiple steps including leaching, evaporation and crystallization. There are many ways for purification such as adding magnesium to remove phosphorus or put through carbon dioxide for pre-carbonization to remove the impurity or adding lime to remove phosphorus, aluminum and silicon. It needs evaporation for twice, cooling, separation, and further drying to obtain the finished product of potassium carbonate. Owing to the limitation in the sources of raw material, this method is not suitable for mass production and it has been eliminated.
Leblanc method: Mix the potassium, coal, limestone in a certain ratio, add water and stir, wherein the potassium chloride is maintained at 6% to 8%, the sodium salt is maintained in 8% to 10% and then subject to calcination at 900~1000 ℃ to obtain the black ash. The black ash is pulverized and subject to hot water extraction. The immersion is further subject to evaporation to precipitate some part of unconverted potassium sulfate out; it was further sent to the carbonation tower for pre-carbonation after separation. Add the potassium permanganate into the carbonation solution to remove the impurities precipitate of aluminum, silicon, and iron; the filtrate was evaporated to the precipitation of potassium carbonate, sodium compound salt and impurities; the clarifying solution further undergoes secondary carbonation to obtain the crude potassium carbonate crystals; it further goes through filtering, water washing, and further calcination at 500~600 ℃ to obtain the finished potassium carbonate product. Its reaction processes are:
K2SO4 + 2C + CaCO3 → K2CO3 + CaS + 2CO2 ↑
K2CO3 + CO2 + H2O → 2KHCO3
2KHCO3 → K2CO3 + CO2 ↑+ H2O
Recrystallization method: dissolve the technical grade potassium carbonate in distilled water for solution purification; remove the impurities through filtration; the filtrate is further subject to concentration by evaporation, cooling crystallization, centrifugation, and drying to obtain the finished product of anhydrous potassium carbonate.


It can be applied to the washing and processing for the pre-exposed photosensitive material.
It is mainly applied to the manufacturing of the kinescope glass of the electronics industry, the decarbonization of fertilizer production, and the manufacturing of potassium salt.
It can be used as analysis reagents, fluxing agent as well as the preparation of various kinds of potassium salts.
It can be used as reagents for analysis, baseline standard reagents and the fluxing agent of molten silicates and insoluble sulfates.
It can be used as a leavening agent in food; it can also be used for glass, printing and dyeing, soap, enamel, preparation of potassium salt, decarbonylation of synthetic ammonia as well as being applied to color TV industry.
It can be used as an alkaline agent and dough conditioner, and can also inhibit the souring of noodles. It can be applied to pasta food. Apply it in appropriate amount according to production requirement.
It can be used for the production of optical glass and can increase the transparency, strength and refractive co-efficiency of the glass. It can also be used in the production of welding electrodes and can prevent the phenomenon of breaking arc during welding. It can be used for the production of vat dyes and dyeing and the white discharge of ice dyeing. It can be used as the absorbent for removing hydrogen sulfide and carbon dioxide. When being mixed with soda ash, it can be used as a dry powder extinguishing agent.
It can also be used as the auxiliary material of acetone, and alcohol production and the antioxidant in the production of rubber. Its aqueous solution can be used for the scouring of cotton and the degreasing of wool. In addition, it can also be applied to the production of inks, pharmaceutical for photography, polyester, electroplating, leather, ceramic, building materials, crystal, potassium soap and medicine. Heavy potassium carbonate is mainly used as the raw material of production of kinescope glass shell and is widely used as the raw material of glass and special glass materials as well as being used for the decarbonization of chemical fertilizer.



Potassium carbonate is a white, crystalline, salt that forms basic aqueous solutions used in the production of fertilizer, glass, ceramics, explosives, soaps, chemicals, and wool treatments. It was the main compound once referred to as potash, although the term today is not reserved exclusively for potassium carbonate, but for several potassium salts. In the fertilizer industry potash refers to potassium oxide, K2O, rather than potassium carbonate.Pearlash is a purer form of potash made by heating potash to remove impurities.

Chemical Properties

white powder or granules


It is used as drying agent for organic solvents; a base.


Potassium Carbonate is a general purpose food additive and alkali. it is hygroscopic and the aqueous solutions are strongly alkaline. it has a solubility of 1 g in 1 ml of water at 25°c. it is used as a flavoring agent and processing aid, and to control ph. it is used in soups to neutralize acidity.


Potassium carbonate is used for numerous applications. Its primary use is in the production of specialty glasses and ceramics. It is used to make optical glass, glass used for video screens in televisions and computers, and laboratory glassware. Its is used in certain glasses rather then cheaper sodium carbonate owing to its better compatibility with lead, barium, and strontium oxides incorporated in these glasses. These oxides lower the melting point of glass and produce a softer glass. Potassium carbonate has a higher refractive index than sodium carbonate producing a more brilliant glass. Potassium carbonate is a common flux combined with titanium dioxide to produce frits used in ceramics. A frit is a calcined mixture of fine silica, a pigment, and a flux that is ground a specific particle size and used to produce glazes, enamels, and additives in glass making.
Potassium carbonate is used in agriculture and food production. Potassium carbonate is used as a spray or drip fertilizer and also as a constituent of compound fertilizers. Its high water solubility and alkaline property make it useful for supplying potassium to acidic soils, especially in vineyards and orchards. Dutch-processed cocoa uses potassium carbonate as an alkalizing agent to neutralize the natural acidity of cocoa. It is used to produce food additives like potassium sorbate and monopotassium phosphate.
Potassium carbonate is used in the chemical industry as a source of inorganic potassium salts (potassium silicates, potassium bicarbonate), which are used in fertilizers, soaps, adhesives, dehydrating agents, dyes, and pharmaceuticals. Potassium carbonate used to make potassium lye produces soft soaps, which are liquids or semisolids rather than solids. Other uses of potassium carbonate includes use as a fire suppressant in extinguishers, as a CO2 absorbent for chemical processes and pollution control, an antioxidant in rubber additives, and in pharmaceutical formulations.


ChEBI: A potassium salt that is the dipotassium salt of carbonic acid.

Production Methods

The name potash comes fromthe traditional method of making potassium carbonate, which has been performed sinceancient times. Preparing potassium carbonate involved burning wood or other plant material,leaching the ashes in a wooden barrel covered on its bottom with straw, and then evaporatingor boiling away the water in the leachate in clay or iron pots to recover potassium and sodiumalkalis.

General Description

An aqueous solution of potassium hydroxide. Corrosive to metals and tissue. Density 12.8 lb /gal. Used to make soaps, other potassium compounds, in liquid fertilizers.

Air & Water Reactions

Water soluble. Addition of water evolves heat.

Reactivity Profile

Potassium carbonate neutralizes acids exothermically to form salts plus water. Reacts with certain metals (such as aluminum and zinc) to form oxides or hydroxides of the metal and generate gaseous hydrogen. May initiate polymerization reactions in polymerizable organic compounds, especially epoxides. May generate flammable and/or toxic gases with ammonium salts, nitrides, halogenated organics, various metals, peroxides, and hydroperoxides. May serve as a catalyst. Reacts when heated above about 84°C with aqueous solutions of reducing sugars other than sucrose, to evolve toxic levels of carbon monoxide [Bretherick, 5th Ed., 1995].


Solutions irritating to tissue.

Health Hazard

TOXIC; inhalation, ingestion or skin contact with material may cause severe injury or death. Contact with molten substance may cause severe burns to skin and eyes. Avoid any skin contact. Effects of contact or inhalation may be delayed. Fire may produce irritating, corrosive and/or toxic gases. Runoff from fire control or dilution water may be corrosive and/or toxic and cause pollution.

Fire Hazard

Non-combustible, substance itself does not burn but may decompose upon heating to produce corrosive and/or toxic fumes. Some are oxidizers and may ignite combustibles (wood, paper, oil, clothing, etc.). Contact with metals may evolve flammable hydrogen gas. Containers may explode when heated.

Agricultural Uses

Potassium carbonate (K2C03) in solution form can be used as a liquid fertilizer. A limited quantity of the solid is used as a non-chloride form of potassium for tobacco.
Potassium carbonate is obtained from ash. It is made by electrolysis of potassium chloride. Potassium hydroxide on reaction with carbon dioxide gives potassium carbonate. Liquid carbonate contains about 50% potassium carbonate in water. The solid product, which contains over 70% potassium carbonate is fairly expensive and is of use in only limited types of acid soil. Neutralizing caustic potash with carbon dioxide gas also produces potassium carbonate.

Agricultural Uses

The term potash designates potassium oxide (K2O). Potassium oxide is never used as such in fertilizers. The term potash is loosely applied to potassium salts, but it generally refers to potassium carbonate (K2C03), or potassium chloride (KCl). Potash in fertilizers is usually present in the form of a muriate or sulphate, and occasionally in the form of a carbonate or nitrate.
The ores of naturally occurring potassium salts are called potash ores. Low-grade potash materials are kainite, basalt, sylvinite, carnalite and schoenite. The potassium content of fertilizers is expressed as percent potash (K2O)

Safety Profile

Poison by ingestion. A strong caustic. Incompatible with KCO, chlorine trifluoride, magnesium. Mutation data reported. When heated to decomposition it emits toxic fumes of K2O.

Purification Methods

It crystallises from water between 100o and 0o. The solubility in H2O is 105% at 0o, 127% at 60o and 205% at 135o (b of saturated solution). After two recrystallisations of technical grade material, it had B, Li and Fe at 1.0, 0.04 and 0.01 ppm, respectvely. [D.nges in Handbook of Preparative Inorganic Chemistry (Ed. Brauer) Academic Press Vol I p 987 1963.]


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Basic information Description Outline Reference quality standards Content Analysis Solubility of potassium carbonate in water Toxicity Limited use Chemical Properties Production method Uses References Safety Related Supplier