Potassium hydroxide, also called caustic potash, is a chemical compound with the formula KOH. The purified material is a white solid that is commercially available in the form of pellets and flakes. Similar to sodium hydroxide (caustic soda, NaOH), it is a strong alkali, very soluble in water, and highly corrosive. It is useful for a variety of applications, including the manufacture of soaps, biodiesel, batteries, fuel cells and fertilizers.
Preparation of Salts
Being strongly alkaline, potassium hydroxide reacts with various acids, and this acid-base reaction is used for the production of potassium salts. These salts, in turn, have a number of different applications. For example, the phosphates of potassium are fertilizers, the carbonate is used in the manufacture of soap and glass, the cyanide is used in gold mining and electroplating, and the permanganate is a disinfectant.
Neutralization of Acids
As an alkali, potassium hydroxide is used to neutralize acidity and adjust the pH of solutions. In chemical analyses, it is a valuable agent for the titration of acids to determine their concentration.
Production of Soaps
The reaction of potassium hydroxide with oils and fats under heated conditions is called saponification. This reaction is useful for the production of potassium soaps, which are softer and more soluble than soaps derived with sodium hydroxide. Consequently, liquid soaps tend to be potassium soaps, while solid soaps tend to be sodium soaps.
Manufacture of Batteries and Fuel Cells
An aqueous solution of potassium hydroxide is used as the electrolyte in various types of batteries, including alkaline, nickel-cadmium, and manganese dioxide-zinc batteries. It is also an electrolyte in certain types of fuel cells. Potassium hydroxide solutions are better conductors of electricity than sodium hydroxide solutions and are therefore preferred over the latter.
Potassium hydroxide is a catalyst in the process of manufacturing biodiesel from oils and fats. In the manufacture of paper, it helps separate lignin from cellulose fibers. It is an etchant in the wet processing of semiconductors and a bleaching agent for textiles. It can be used for the absorption of carbon dioxide (CO2), sulfur trioxide (SO3), and nitrogen trioxide (NO3) in gas streams. It is also used for unclogging drains, removing hair from animal hides, and dissolving animal carcasses. In the food industry, it may be used in the processing of chocolate and cocoa, the production of caramel color, and the washing and chemical peeling of fruits and vegetables.
About the Author
Dinshaw Dadachanji has been a science editor and writer for more than 14 years. He has a Ph.D. in molecular biology from Yale University. His articles have been published by "The World & I" magazine and the Institute of Human Virology, among others.
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