Description Chemical Properties Uses Production method Reference quality standards Content Analysis Solubility of potassium carbonate in water Toxicity Limited use References

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Potassium carbonate structure

CAS No. 584-08-7 Chemical Name: Potassium carbonate Synonyms K2CO3;K-Gran;POTASH;PEARL ASH;Pearl dust;Sal absinthii;Kaliumcarbonat;SALT OF TARTAR;Montreal potash;alt of wormwood CBNumber: CB4853879 Molecular Formula: K2CO3 Formula Weight: 138.21 MOL File: 584-08-7.mol
Melting point: 891 °C (lit.) Boiling point: decomposes Density 2.43 g/mL at 25 °C storage temp. Store at +5°C to +30°C. solubility H2O: 1 M at 20 °C, clear, colorless form powder Specific Gravity 2.29 color Yellow PH 11.5-12.5 (50g/l, H2O, 20℃) Water Solubility 1120 g/L (20 ºC) λmax λ: 260 nm Amax: 0.03λ: 280 nm Amax: 0.02 Sensitive Hygroscopic Merck 14,7619 BRN 4267587 Stability: Stable. Incompatible with moisture, acids, magnesium bromine trifluoride and magnesium bromine trichloride. SCOGS (Select Committee on GRAS Substances) Potassium carbonate CAS DataBase Reference 584-08-7(CAS DataBase Reference) FDA 21 CFR 184.1619; 582.1619; 173.310; 310.545 Substances Added to Food (formerly EAFUS) POTASSIUM CARBONATE EWG"s Food Scores 1 FDA UNII BQN1B9B9HA NIST Chemistry Reference Dipotassium carbonate(584-08-7) EPA Substance Registry System Potassium carbonate (584-08-7)

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Potassium carbonate Chemical Properties,Uses,Production


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.

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.


Potassium carbonate 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.Potassium carbonate 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.Potassium carbonate 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.

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 + NaClR-K + NH4HCO3 → R-NH4 + KHCO32KHCO3 → K2CO3 + CO2 ↑+ H2OLeblanc 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 → 2KHCO32KHCO3 → K2CO3 + CO2 ↑+ H2ORecrystallization 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.

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

Potassium carbonate, potash, pearl ash, K2CO3, white solid, soluble, formed (1) in the ash when plant materials are burned, (2) by reaction of potassium hydroxide solution and the requisite amount of CO2.

Chemical Properties

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.


Used (1) in making special glasses, (2) in the making of soft soap, (3) in the preparation of other potassium salts (a) in solution, (b) upon fusion; potassium hydrogen carbonate, potassium bicarbonate, potassium acid carbonate, KHCO3, white solid, soluble, (4) in vat dyeing and textile printing, (5) in titanium enamels, (6) in boiler water treating compounds, (7) in photographic chemical formulations, (8) in electroplating baths, and (9) as an important absorbent for CO2 in the process industries.


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.

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.


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

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 .


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 beused as a liquid fertilizer. A limited quantity of the solidis used as a non-chloride form of potassium for tobacco.Potassium carbonate is obtained from ash. It is madeby electrolysis of potassium chloride. Potassiumhydroxide on reaction with carbon dioxide givespotassium carbonate. Liquid carbonate contains about50% potassium carbonate in water. The solid product,which contains over 70% potassium carbonate is fairlyexpensive and is of use in only limited types of acid soil.Neutralizing caustic potash with carbon dioxide gas alsoproduces potassium carbonate.

Safety Profile

Poison by ingestion. Astrong caustic. Incompatible with KCO,chlorine trifluoride, magnesium. Mutationdata reported. When heated todecomposition 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.

Potassium carbonate Preparation Products And Raw materials

Raw materials