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CAS Number 1310-58-3
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Linear Formula KOH
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Molecular Weight 56.11
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EC Number 215-181-3
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MDL number MFCD00003553
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PubChem Substance ID 329820239
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eCl@ss 38100303
Potassium hydroxide is an inorganic
compound with the formula KOH, and is
commonly called caustic potash.
Detailed description
Along
with sodium hydroxide (NaOH), this
colorless solid is a prototypical strong base. It has many industrial and niche
applications, most of which exploit its corrosive nature and its reactivity
toward acids. An estimated
700,000 to 800,000 tonnes were produced in 2005. Approximately 100 times more NaOH than
KOH is produced annually.[10] KOH is
noteworthy as the precursor to most soft and liquid soaps as well as numerous potassium-containing chemicals.
Uses
KOH and NaOH can be used interchangeably for a
number of applications, although in industry, NaOH is preferred because of its
lower cost.
Precursor to other potassium compounds
Many potassium salts are prepared by neutralization
reactions involving KOH. The potassium salts of carbonate, cyanide, permanganate, phosphate, and various
silicates are prepared by treating either the oxides or the acids with KOH.[10] The high solubility
of potassium phosphate is desirable in fertilizers.
Manufacture of biodiesel
Although more expensive than using sodium hydroxide,
KOH works well in the manufacture of biodiesel by transesterification of the triglycerides
in vegetable
oil. Glycerin from potassium
hydroxide-processed biodiesel is useful as an inexpensive food supplement for
livestock, once the toxic methanol is removed.[16]
Manufacture of soft soaps
The saponification of fats with KOH is used to
prepare the corresponding "potassium soaps," which are softer than the more common sodium
hydroxide-derived soaps. Because of their softness and
greater solubility, potassium soaps require less water to liquefy, and can thus
contain more cleaning agent than liquefied sodium soaps.[17]
As an electrolyte
Aqueous potassium hydroxide is employed as the electrolyte in alkaline
batteries based on nickel-cadmium, nickel-hydrogen, and manganese
dioxide-zinc. Potassium hydroxide is preferred over sodium
hydroxide because its solutions are more conductive.[18] The Nickel Metal Hydride batteries in the Toyota
Prius use a mixture of potassium hydroxide and sodium hydroxide.[19] Nickel–iron batteries also use potassium
hydroxide electrolyte.
Niche applications
Like sodium
hydroxide, potassium hydroxide attracts numerous specialized
applications, virtually all of which rely on its properties as a strong
chemical base with its consequent ability to degrade many materials. For
example, in a process commonly referred to as "chemical cremation" or
"resomation," potassium
hydroxide hastens the decomposition of soft tissues, both animal and human, to
leave behind only the bones and other hard tissues.[20] Entomologists wishing to study the
fine structure of insect anatomy may use a 10%
aqueous solution of KOH to apply this process.[21]
In chemical synthesis, the choice between the use of
KOH and the use of sodium
hydroxide, NaOH, is guided by the solubility of the resulting salt.
The corrosive properties of potassium hydroxide make
it a useful ingredient in agents and preparations that clean and disinfect surfaces and
materials that can themselves resist corrosion by KOH.[22]
KOH is also used for semiconductor chip fabrication. See also: anisotropic wet etching.
Potassium hydroxide is often the main active
ingredient in chemical "cuticle removers" used in manicure treatments.
Because aggressive bases like KOH damage the cuticle of the hair shaft, potassium
hydroxide is used to chemically assist the removal of hair from animal hides.
The hides are soaked for several hours in a solution of KOH and water to
prepare them for the unhairing stage of the tanning process. This same
effect is also used to weaken human hair in preparation for shaving. Pre-shave
products and some shave creams contain potassium hydroxide to force open the
hair cuticle and to act as a hygroscopic agent to attract and force water into
the hair shaft, causing further damage to the hair. In this weakened state, the
hair is more easily cut by a razor blade.
Potassium hydroxide is used to identify some species
of fungi. A 3–5% aqueous solution of KOH is applied to the flesh of a
mushroom and the researcher notes whether or not the color of the flesh
changes. Certain species of gilled
mushrooms, boletes, polypores, and lichens[23] are identifiable
based on this color-change reaction.[24]
Petroleum refineries
Potassium hydroxide is also used in petroleum and
natural gas refining for removal of organic acids and sulfur compounds.
PRICE
$192.93/KG OR $87.69/IB
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