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• Description

  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.
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• 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.;

• Uses

  Potassium carbonate can serve as an effective alkaline agent and dough conditioner and is capable of hindering the fermentation process in noodles. It can be applied to pasta food, where its application quantity must be in accordance with production requirements. In addition, potassium carbonate can be used for the production of optical glass, as it enhances the transparency, strength, and refractive coefficient of the material. It is also useful as a welding electrode, preventing arc-breaking during welding. Further applications of potassium carbonate include its utility as a vat dye and as a white discharging agent for ice dyeing. It can be utilized as an absorbent for removing carbon dioxide and hydrogen sulfide, and quantities can be mixed with soda ash to create a dry powder extinguishing agent.;

• 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
  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. ;

• 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) ;

• Toxicity

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

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