potassium hydroxide

 

chemical compound with formula KOH. Pure potassium hydroxide forms white, deliquescent crystals. For commercial and laboratory use it is usually in the form of white pellets. A strong base, it dissolves readily in water, giving off much heat and forming a strongly alkaline, caustic solution (see acids and bases). It is commonly called caustic potash. It closely resembles sodium hydroxide in its chemical properties and has similar uses, e.g., in making soap, in bleaching, and in manufacturing chemicals, but is less widely used because of its higher cost. It is prepared chiefly by electrolysis of potassium chloride; commercial grades of it sometimes contain the chloride as well as other impurities.

Potassium hydroxide
Other names	Potash lye
Identifiers
CAS number	1310-58-3
RTECS number	TT2100000
Properties
Molecular formula	KOH
Molar mass	56.10564 g/mol
Appearance	white solid, deliquescent
Density	2.044 g/cm³, solid
Melting point	360 °C
Boiling point	1320 °C
Solubility in water	1100 g/L (25 °C)
Basicity (pKb)	-2.29
Structure
Crystal structure	monoclinic
Hazards
EU classification	Corrosive (C)
NFPA 704	0 3 1
R-phrases	R22, R35
S-phrases	(S1/2), S26, S36/37/39, S45
Flash point	non flammable
Related Compounds
Other anions	Potassium oxide; Potassium peroxide; Potassium superoxide
Other cations	Lithium hydroxide; Sodium hydroxide; Rubidium hydroxide; Caesium hydroxide
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references

The chemical compound potassium hydroxide (KOH), sometimes known as caustic potash, potassa, potash lye, and potassium hydrate, is a metallic base. It is very alkaline and is a "strong base", along with sodium hydroxide, lithium hydroxide, calcium hydroxide, barium hydroxide and strontium hydroxide.

Uses

Agriculture

• Correction of the pH of acidic soils^[1]
• As a fungicide^[2]
• As a herbicide^[3]

Manufacturing and commercial chemical processes

KOH is a major industrial chemical because it is used as a base in a wide variety of chemical processes. Some uses of KOH include:

• Acrylate ester copolymer coating
• defoaming agents used in the manufacture of paper ^[4]
• saponifying oils for liquid soap
• Formulation aid for food^[5]
• pH control agent (raises pH by neutralizing acids)
• Making polyethylene resins
• Textile processing
• As a catalyst in reactions like the production of biodiesel^[6].
• Manufacture of many cleaning products^[7], such as:
  • Washing powders
  • Cleansers (for tubs, tile, etc)
  • Some denture cleaners
  • Non-phosphate detergents
  • Drain or pipe cleaners (clog dissolvers)
  • Widely used in carpet cleaning degreasers
• Manufacture of alkaline batteries, which use an aqueous solution of KOH as an electrolyte^[8]. Thus, potassium hydroxide helps to power flashlights, smoke detectors, and other battery-powered household items.
• As an anisotropic etchant of silicon^[9], exposing octahedral planes. This technique can create pyramids^[10] and regularly-shaped etch pits for uses such as microelectromechanical systems systems.

Medicine (human and veterinary)

• KOH test^[11] (to diagnose fungal infections).
• Whiff test^[12] (to diagnose bacterial vaginosis).
• wart and cuticle solvent.
• (veterinary medicine) disbudding calves horns; dissolving scales and hair.

Food preparation

Food uses of KOH include:

• Washing or chemical peeling of fruits and vegetables
• Chocolate and cocoa processing
• Caramel color production
• Poultry scalding
• Soft drink processing
• Thickening ice cream
• Soaking of olives to soften them and neutralize natural acids
• Glazing of pretzels and German lye rolls before baking to make them crisp.
• Soaking of cod to make the Scandinavian delicacy known as lutefisk (from lutfisk, "lye fish"). Cod is soaked in KOH to a jelly-like consistency, then served with bacon fat, potatoes, brown cheese (brunost) sauce and mushy peas.
• Making of hominy, which is dried maize (corn) kernels reconstituted by soaking in KOH.

See also

• Soda lime

References

1. ^ http://www.potassium-hydroxide.com
2. ^ http://www.weichtiere.at/Mollusks/Schnecken/weinberg.html
3. ^ http://www.hydroponicsearch.com/Explore_the_Science_of_Hydroponics/Plants/Potassium_hydroxide/
4. ^ http://www.p2pays.org/ref%5C02/01258.pdf
5. ^ http://www.codexalimentarius.net/gsfaonline/additives/details.html?id=311
6. ^ http://biodieselmagazine.com/article.jsp?article_id=462
7. ^ http://www.howtobrew.com/section1/chapter2-2-1.html
8. ^ http://www.powerstream.com/BatteryFAQ.html
9. ^ http://snf.stanford.edu/Materials/ChemFiles/KOHEtch.html
10. ^ http://dx.doi.org/10.1016/j.sna.2003.11.013
11. ^ http://dermatology.about.com/library/bldefpothyrox.htm
12. ^ http://www.jabfm.org/cgi/content/full/18/6/561

External links

• Newscientist article dn10104
• MSDS from JTBaker
• Reheis [1]
• Making lye from ashes

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