Potassium Hydroxide

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Created by: Team Chemistry - Examples.com, Last Updated: April 28, 2024

Potassium Hydroxide

Potassium hydroxide, often known as KOH, is a strong, inorganic compound that plays a crucial role in various scientific and industrial applications. This white solid is highly alkaline and is commonly referred to as caustic potash. It’s widely used in the production of soaps, detergents, and cleaning agents because of its ability to effectively break down organic materials. In the laboratory, potassium hydroxide is essential for chemical analysis and pH control. Due to its corrosive nature, it is important to handle KOH with care, ensuring proper safety measures such as wearing gloves and goggles are in place. This compound is not only fundamental in manufacturing processes but also in environmental management and agriculture, where it helps regulate acidity levels in soils and water.

What is Potassium Hydroxide?

Potassium hydroxide is often abbreviated as KOH and it is a powerful chemical base widely used in various industries and applications. It appears as a white, solid substance that dissolves readily in water, producing heat and forming a solution known as lye. This compound is fundamental in manufacturing soap, detergents, and cleaning agents. It also plays a crucial role in the production of biodiesel, the buffering of acids in cosmetics, and even in food processing, where it adjusts pH levels. As a base, potassium hydroxide is highly reactive, especially with acids, where it neutralizes them to form water and salts. Its versatility and effectiveness make it an essential chemical in many fields.

Chemical Names and Formulas

Hill FormulaHKO
NamePotassium hydroxide
Alternate NamesCaustic Potash, Kaliumhydroxid, Potassa, Potassium Hydrate

Structure of Potassium Hydroxide


Potassium hydroxide is represented by the chemical formula KOH and it has a simple ionic structure consisting of potassium ions (K⁺) and hydroxide ions (OH⁻). In its solid form, these ions are arranged in a crystal lattice, which is a highly organized structure that helps stabilize the compound. When dissolved in water, potassium hydroxide breaks apart into its constituent ions, which makes it a strong base capable of conducting electricity. This ionic dissolution is crucial for its many uses in chemical reactions and industrial processes, such as soap making and as an electrolyte in batteries.

Preparation of Potassium Hydroxide

Potassium hydroxide (KOH) is commonly prepared through the electrolysis of potassium chloride (KCl) solution, a process that involves passing an electric current through the solution to cause a chemical reaction. During this process, potassium chloride, which is salt-like and dissolves well in water, breaks down into potassium ions (K⁺) and chloride ions (Cl⁻). The potassium ions move towards the negative electrode (cathode) where they gain electrons to form potassium metal. Simultaneously, at the positive electrode (anode), water molecules lose electrons and produce hydroxide ions (OH⁻) and hydrogen gas (H₂).

The chemical equation for this reaction is:

2KCl(aq) + 2H₂O(l) → 2KOH(aq) + Cl₂(g) + H₂(g)

In this equation, KCl and H₂O react to form KOH, along with chlorine gas (Cl₂) and hydrogen gas (H₂) as byproducts. The resulting Potassium Hydroxide solution is often concentrated by evaporating the water, leaving behind the solid KOH. This method is highly efficient and widely used in industrial settings to produce potassium hydroxide, which serves various purposes from manufacturing soaps and detergents to serving as an electrolyte in batteries.

Physical Properties of Potassium Hydroxide

AppearanceWhite or slightly yellow solid with a lumpy or flaky texture
OdorIt is typically odorless, making it distinct in this respect
SolubilityHighly soluble in water, forming a solution called lye
Melting PointAbout 360°C (680°F), indicating its stability under heat
Boiling PointAround 1320°C (2408°F), very high, showing it can withstand extreme temperatures
DensityApproximately 2.04 g/cm³, making it denser than water
ConductivityGood conductor of electricity when dissolved in water
CorrosivenessHighly corrosive, especially to metals and living tissues

Chemical Properties of Potassium Hydroxide

Strong Base

  • Potassium Hydroxide is a very strong base, meaning it readily accepts protons. This property makes it highly reactive with acids to form water and salts, a type of reaction known as Neutralization. For example, when KOH reacts with hydrochloric acid (HCl), they form Potassium chloride (KCl) and water (H₂O).
  • Equation: KOH + HCl → KCl + H₂O


  • KOH is Hygroscopic, which means it absorbs moisture from the air. This characteristic is crucial in applications that require moisture control, like in certain chemical manufacturing processes.

Reactivity with Carbon Dioxide

  • Potassium Hydroxide reacts with carbon dioxide (CO₂) to form Potassium Carbonate (K₂CO₃). This reaction is beneficial in processes where CO₂ needs to be removed from the environment, such as in air purification systems.
  • Equation: 2 KOH + CO₂ → K₂CO₃ + H₂O


  • One of the most well-known reactions involving KOH is saponification, where it reacts with fats or oils to produce soap. This reaction results in the formation of Glycerol andPotassium salt of fatty acids (soap).
  • Equation: KOH + Fat/Oil → Glycerol + Potassium Soap

Potassium Hydroxide (KOH) Chemical Compound Information

Chemical Identifiers

CAS registry number1310-58-3
PubChem compound ID6093213
SMILES identifier[OH-].[K+]
InChI identifierInChI=1/K.H2O/h;1H2/q+1;/p-1/fK.HO/h;1h/qm;-1
EU number215-181-3
Gmelin number19033
RTECS numberTT2100000

NFPA Label

NFPA health rating3
NFPA fire rating0
NFPA reactivity rating1

Uses of Potassium Hydroxide


Soap and Detergent Manufacturing

Potassium Hydroxide is crucial in making soft soaps and liquid detergents. Its ability to react with fats and oils in a process called saponification results in soap that is highly effective in cleaning.

Fertilizer Production

KOH is used in the agricultural sector to produce potassium-containing fertilizers. These fertilizers are essential for plant growth and crop yield improvement.

Battery Making

In battery production, Potassium Hydroxide acts as an electrolyte in alkaline batteries. It facilitates the flow of electricity by allowing ions to move freely within the battery.

Food Industry

Potassium Hydroxide adjusts pH levels in various food processing applications. It helps in the preparation of cocoa and chocolate by making them less acidic.

Cleaning Agents

Due to its strong base properties, KOH is used in commercial and industrial cleaners, including drain openers and oven cleaners, to break down organic materials.

Biodiesel Production

In biodiesel industries, potassium hydroxide is used as a catalyst to convert fats and oils into biodiesel through a process called transesterification.

Pharmaceutical Industry

KOH finds applications in the pharmaceutical industry, where it is used to produce soft gels and various drug formulations.

Water Treatment

KOH is also employed in water treatment processes to remove hardness and neutralize acidic water.

Side Effects of potassium Hydroxide

  • Skin Irritation: Direct contact with KOH can cause severe irritation, redness, and burns. It can break down the oils in the skin, leading to painful sores or ulcers.
  • Eye Damage: Exposure to KOH can be extremely dangerous to the eyes. It can cause severe irritation and even permanent damage, including blindness, if not washed out immediately and thoroughly.
  • Respiratory Issues: Inhaling fumes or dust containing potassium hydroxide can irritate the respiratory tract, leading to coughing, difficulty breathing, and in severe cases, damage to the lungs.
  • Digestive Harm: Accidental ingestion of KOH can damage the mouth, throat, esophagus, and stomach, causing severe burns, pain, vomiting, and potentially life-threatening injuries.


Is Potassium Hydroxide Good for Your Skin? can cause severe skin irritation and burns; it is not suitable for direct skin application.

Is Potassium Hydroxide Safe for Cleaning?

Yes, Potassium Hydroxide is effective and safe for cleaning when used properly and with appropriate protective measures.

What Happens When You Mix Potassium Hydroxide and Water?

Mixing KOH with water results in an exothermic reaction, releasing heat and forming a solution called lye.

What Happens When You Mix Potassium Hydroxide and Vinegar?

Mixing KOH with vinegar, an acid, produces a neutralization reaction, yielding water and potassium acetate, a type of salt.

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