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Thursday, 5 January 2017

How to make potassium hydroxide or caustic potash - WorldOfChemicals

Potassium Hydroxide or caustic potash is an extremely versatile cleaning agent. It is highly basic, forming strongly alkaline solutions in water and other polar solvents.These solutions are capable of deprotonating many acids, even weak ones. In analytical chemistry, titrations using solutions of Potassium hydroxide are used to assay acids.

Potassium Hydroxide is hygroscopic, so be sure to keep it in a sealed container in a cool dry place. If you leave it in an open container for even a day, it can attract enough moisture to throw off its weight enough to ruin a recipe. If you leave it out for an extended period of time, it can attract enough moisture from the air in the room to turn completely liquid. When handling Potassium Hydroxide, give it the same safety considerations as you would with Sodium Hydroxide. It is a hazardous material, and being educated about safe handling practices is key when handling Potassium Hydroxide.

It can be found in pure form by reacting sodium hydroxide with impure potassium. It is usually sold as translucent pellets, which will become tacky in air because KOH is hygroscopic.

Potassium Hydroxide can exhibit high thermal stability. The gaseous species of this chemical is dimeric.Because of its high stability and relatively low melting point, it is often melt-cast as pellets or rods, forms that have low surface area and convenient handling properties.

It serves as a source of OH-, a highly nucleophilic anion that attacks polar bonds in both inorganic and organic materials.

Manufacturing Process

Earlier it was made by adding potassium carbonate (potash) to a strong solution of calcium hydroxide (slaked lime), leading to a metathesis reaction which caused calcium carbonate to precipitate, leaving potassium hydroxide in solution:

Ca(OH)2 + K2CO3 → CaCO3 + 2 KOH

Filtering off the precipitated calcium carbonate and boiling down the solution gives potassium hydroxide. It was the most important method of producing potassium hydroxide until the late 19th century when it was largely replaced by the current method of electrolysis of potassium chloride solutions. The method is analogous to the manufacture of sodium hydroxide

2 KCl + 2 H2O → 2 KOH + Cl2 + H2

Hydrogen gas forms as a by-product on the cathode; concurrently, an anodic oxidation of the chloride ion takes place, forming chlorine gas as a by-product. Separation of the anodic and cathodic spaces in the electrolysis cell is essential for this process.


From alkaline batteries to agrochemicals, food additives to soap and detergents, oil and gas drilling to de-icing fluids there are huge applications of the potassium hydroxide or commercially called as caustic potash, than most people are aware.

Some of the principal products or processes in which caustic potash is used, are:

A dehydrating agent for drying gases
A lubricant in the extrusion pressing of high melting alloys
A scavenger in a gasoline treating process (dual layer) for removing mercaptans
A methylating agent
An alkaline builder in detergent formulations
In refining petroleum fractions
In removing insulating coatings from wire
In purifying olefin feedstock containing hydrocarbons prior to polymerization
In stabilising synthetic lubricants
In removing naphthenic acids from gas oils
In fertilizers
In descaling ferrous metals
In sweetening sour petroleum fractions
In a fused alkaline salt mixture used for metal cleaning
In lye peeling
In electrolytic stripping baths
In chemical compounding
In a molten bath for removing polyesters and polyurethanes from steel objects
In an absorption cartridge for scavenging carbon dioxide
As a chemical desiccant
As a cleaner for eliminating scale from the surface of titanium alloy intermediates
As an agent for lowering the sulfur content of coal
In alkaline batteries
Read More: How to make potassium hydroxide or caustic potash - WorldOfChemicals

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