How Is Potassium Carbonate Made? Production Methods Explained
Potassium Carbonate is an inorganic compound having the chemical formula K2CO3 and the chemical name Potassium carbonate. It is otherwise called Carbonate of potash, or Pearl ash, or Di-potassium carbonate. It is defined as a dipotassium salt of carbonic acid and can be widely used in the production of soap and glass.
Pearl ash is a hygroscopic and deliquescent white powder. It is odourless and tastes the same as alkaline. It is readily soluble in water but insoluble in acetone, alcohol, and ethanol. It contains a pH of 11.6. It is a primary component of potash.
Properties of Potassium Carbonate – K₂CO₃
Let us look at the important properties of Potassium Carbonate as listed below:
Potassium Carbonate Properties
Potassium Carbonate Structure – K₂CO₃
The Potassium Carbonate Structure can be illustrated as follows:
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History
Historically, the Di-potassium carbonate compound was created by baking potash in a kiln. The white powder, which was produced, was the potassium carbonate. In 1790, Samuel Hopkins was awarded the first patent, issued by the US Patent Office for an improved process of making potash and pearl ash.
Production of Potassium Carbonate
Potassium Carbonate can be prepared commercially by reacting the potassium hydroxide (KOH) compound with carbon dioxide (CO2). The chemical reaction for the same can be given as follows:
2 KOH + CO2 → K2CO3 + H2O
An alternative process to obtain potassium carbonate is by treating it with carbon dioxide (CO2) in an organic amine presence, which results in the potassium bicarbonate, and on further calcination of KHCO3 produces potassium carbonate. The chemical reaction for the same can be given as follows:
2 KHCO3 → K2CO3 + H2O + CO2
Uses of Potassium Carbonate
Let us look at the use of potassium carbonate as listed below:
In the basic inorganic chemical industry, light industry and medicine industry, Potassium carbonate is treated as an important raw material. It has been primarily used in the production of electrode tube, optical glass, TV tube, printing items, bulb, dye, photography items, ink, sodium metasilicate, plating, polyester powder, leather, crystal, potash soap, drugs, and ceramic building materials.
On the other side, it can also be used as a dry powder, rubber protective agent, and gas adsorbent.
This compound can be used for carbon dioxide removal in chemical fertilizer syngas.
This is also used as a potassic fertilizer.
Potassium carbonate also extends its application in various fields such as gourmet, food, and detergent builder.
Potential Health Effects
Skin Contact: Exposure of potassium carbonate to the skin can cause irritation and redness. This material is not given as a skin sensitizer according to the studies with guinea pigs.
Eye Contact: Eye exposure can cause redness and severe irritation to the eyelids, conjunctiva. Prolonged and untreated eye contact may cause severe and permanent eye damage.
Ingestion: Ingestion of this compound can cause oesophagal, oral, glottis redness, ulceration, irritation, stomach & intestinal irritation, edema, and burns. Ingesting in excess quantities can also cause vomiting, ulceration, shock, and even death.
Inhalation: Inhalation of this material may cause upper airway irritation, cough, redness of mouth, including upper airways.
Applications Potassium Carbonate
Let us look at the important applications of potassium carbonate:
As a mild drying agent where the other drying agents, like magnesium sulfate and calcium chloride. It may be incompatible and is not suitable for the acidic compounds. However, it can be useful in drying an organic phase if one contains a small amount of acidic impurity. It can also be used to dry some of the alcohols, ketones, and amines before distillation.
In cuisine, where it has several traditional uses, it is also an ingredient in grass jelly production, which is food consumed in Southeast Asian and Chinese cuisines, and Chinese hand-pulled noodles and moon cake as well. Also, it is used to tenderize tripe. Often, German gingerbread recipes use potassium carbonate as a baking agent, although with a hartshorn combination. Potassium carbonate usage must be limited to a specific amount to prevent harm and advised not to be used without guidance.
In the cocoa powder, the alkalization can produce Dutch process chocolate by balancing the pH (it means, reduce the acidity) of natural cocoa beans; it enhances aroma. The adding of the potassium carbonate process to cocoa powder is generally called "Dutching" (and the products are called Dutch-processed cocoa powder). The process was first developed in 1828 by Dutchman Coenraad Johannes van Houten.
Potassium Carbonate's Food Safety
While not every potassium carbonate is safe to add with food, commercially, food-grade potassium carbonate is available. It is safe to add the same potassium carbonate to food. Of course, potassium carbonate is reasonably a strong base, so it does not taste very good if we had more than just a small amount.
FAQs on Potassium Carbonate (K₂CO₃): Properties, Uses & Health Impacts
1. What is potassium carbonate, and what is its common name?
Potassium carbonate, with the chemical formula K₂CO₃, is an inorganic compound. It is a white salt that is soluble in water. Historically, it was known as potash or pearl ash, as it was created by baking potash in a kiln to remove impurities. It appears as a white, crystalline, or granular powder and is odourless.
2. What are the key physical and chemical properties of potassium carbonate?
Potassium carbonate has several distinct properties that are important for students to know:
- Appearance: It is a white, translucent crystalline solid or granular powder.
- Solubility: It is highly soluble in water (approx. 112 g/L at 20°C) but insoluble in ethanol and acetone.
- Nature of Solution: When dissolved in water, it forms a strongly alkaline (basic) solution due to the hydrolysis of the carbonate ion.
- Melting Point: It has a high melting point of 891 °C (1,636 °F). It decomposes before it can boil.
- Hygroscopic Nature: It is deliquescent, meaning it readily absorbs moisture from the air.
- Density: Its density is approximately 2.43 g/cm³.
3. What is the chemical structure of potassium carbonate (K₂CO₃)?
The chemical structure of potassium carbonate is ionic. It consists of two positively charged potassium ions (K⁺) and one negatively charged carbonate ion (CO₃²⁻). These ions are held together by strong electrostatic forces of attraction, forming an ionic lattice. The carbonate anion itself has a trigonal planar geometry, with the carbon atom at the centre bonded to three oxygen atoms.
4. How is potassium carbonate commercially prepared?
The most common commercial method for preparing potassium carbonate involves the reaction of potassium hydroxide (KOH) with carbon dioxide (CO₂). The reaction is: 2KOH + CO₂ → K₂CO₃ + H₂O. An alternative method, the Engel-Precht process, involves treating potassium chloride (KCl) with magnesium oxide, water, and carbon dioxide under pressure to form a precipitate, which is then decomposed to yield potassium carbonate.
5. What are the main uses of potassium carbonate in various industries?
Potassium carbonate has a wide range of applications. Some important examples include:
- Glass and Soap Manufacturing: It is a primary component in the production of specialty glass (like optical lenses and CRT screens) and soft soaps.
- Drying Agent: In laboratories, it is used as a mild drying agent for some organic compounds, particularly for ketones, alcohols, and amines.
- Food Industry: It is used as a food additive (E501) acting as an acidity regulator, for example, in the production of gingerbread or Chinese noodles.
- Winemaking: It is used as a buffering agent to reduce acidity levels in wine.
- Fire Suppression: It is the main component in Class K fire extinguishers for combating kitchen fires involving oils and fats.
6. Why is an aqueous solution of potassium carbonate basic?
An aqueous solution of potassium carbonate is basic because the carbonate ion (CO₃²⁻) undergoes hydrolysis. The carbonate ion is the conjugate base of a weak acid (bicarbonate, HCO₃⁻). It reacts with water to produce hydroxide ions (OH⁻), which increases the pH of the solution, making it alkaline. The reaction is: CO₃²⁻(aq) + H₂O(l) ⇌ HCO₃⁻(aq) + OH⁻(aq). The presence of these excess hydroxide ions gives the solution its basic properties.
7. How does potassium carbonate's function as a drying agent compare to other agents like anhydrous CaCl₂?
Potassium carbonate (K₂CO₃) is a mild, basic drying agent. This makes it suitable for drying organic liquids that are not acidic. It is less efficient than stronger agents like anhydrous calcium chloride (CaCl₂) or phosphorus pentoxide (P₄O₁₀). The key difference lies in its chemical nature; because K₂CO₃ is basic, it cannot be used to dry acidic solutions as it would react with them. In contrast, CaCl₂ is neutral and has a broader application but may form adducts with alcohols or amines.
8. What are the potential health impacts associated with potassium carbonate exposure?
While generally recognized as safe (GRAS) for use in food, concentrated potassium carbonate can be harmful upon exposure. It is an irritant. Direct contact can cause irritation to the skin, eyes, and respiratory tract. Inhaling the dust can lead to coughing and shortness of breath. Ingestion of large amounts can cause gastrointestinal upset, including nausea and vomiting. Therefore, proper safety precautions like wearing gloves and goggles are important when handling the pure compound.
9. Why does potassium carbonate react with acids like hydrochloric acid (HCl)?
Potassium carbonate reacts with acids because it is a salt of a weak acid (carbonic acid) and a strong base (potassium hydroxide). As a basic salt, it readily undergoes a neutralisation reaction with strong acids like HCl. The carbonate ion acts as a base, accepting protons (H⁺) from the acid. This reaction produces a salt (potassium chloride), water, and carbon dioxide gas, which is seen as effervescence. The balanced chemical equation is: K₂CO₃(aq) + 2HCl(aq) → 2KCl(aq) + H₂O(l) + CO₂(g).
