Everything about Potassium Hydroxide totally explained
| Section2 =
| Section3 =
| Section7 =,
| SPhrases =,,,
| FlashPt = non flammable
}}
| Section8 =
}}
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.
Properties
Pure potassium hydroxide is a colorless, highly
hygroscopic, solid crystalline compound, having density of about 2.04 g/cm
3, readily soluble in water (1 g KOH dissolves in 0.5 g water) and lower alcohols (
methanol,
ethanol,
propanols; solubility in
ethanol being about 1 g KOH/2.5 mL EtOH), as well as other
polar solvents. The dissolution in water is strongly
exothermic, producing substantial amounts of energy in form of heat, leading to temperature rise, sometimes up to boiling point and over; concentrated aqueous solutions are called potassium
lyes.
Manufacture
Of historical relevance is the old method of boiling a solution of
potassium carbonate (potash) with
calcium hydroxide (slaked
lime); the ion transfer reaction takes place, because forming
calcium carbonate is less soluble than lime, precipitating out of the reaction mixture:
Ca(OH)
2 (s), (aq) + K
2CO
3 (aq) → ↓CaCO
3 (s) + 2 KOH
(aq)
precipitated calcium carbonate was than filtered out and the resulting KOH solution boiled down, leaving solid potassium hydroxide ("calcinated or caustic potash"). This method, using potash extracted from wood ashes and slaked lime was known probably already in antique times and was the most important method of producing potassium hydroxide until the late 19th century, when it was largely replaced by the modern method of electrolysis of
potassium chloride solutions, analogous to the method of manufacturing
sodium hydroxide:
» 2 K
+ (aq) + 2H
2O
(l) + 2e
− → ↑H
2 (g) + 2 KOH
(aq)
Hydrogen gas forms as by-product on the
cathode; concurrently, an anodic oxidation of the
chloride ion takes place:
» 2 Cl
– — 2e
− → ↑Cl
2 (g),
forming
chlorine gas as another byproduct. Separation of the anodic and cathodic spaces in the electrolysis cell is essential for this process. For details, see
chloralkali process.
Uses
Agriculture
Biological and medical tests and diagnostics
KOH test (to diagnose fungal infections).
Whiff test (to diagnose bacterial vaginosis).
In botany and mycology, an aqueous solution (typically 10% or less) of KOH is used to rehydrate dried herbarium material in preparation for microscopy.
In palynology, an aqueous solution of KOH is used to deflocculate soil particles aggregated onto pollen grains.
Medical therapeutics (human and veterinary)
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.
Manufacturing and commercial chemical processes
KOH is a major industrial chemical because it's used as a base in a wide variety of chemical processes. Some uses of KOH include:
Acrylate ester copolymer coating
Anti-foaming agent used in the manufacture of paper
saponifying oils for liquid soap
Formulation aid for food
pH control agent (raises pH by neutralizing acids)
Making polyethylene resins
Textile processing
As a catalyst in reactions like the production of biodiesel.
Manufacture of many cleaning products, 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. Thus, potassium hydroxide helps to power flashlights, smoke detectors, and other battery-powered household items.
As an anisotropic etchant of silicon, exposing octahedral planes. This technique can create pyramids and regularly-shaped etch pits for uses such as microelectromechanical systems.
An anisotropic etchant of GaAs, exposing Ga and As planes. This technique can create rectangular etch pits by etching As (111) plane faster.
Further Information
Get more info on 'Potassium Hydroxide'.
|
External Link Exchanges
Do you know how hard it is to get a link from a large encyclopaedia? Well we're different and will prove it. To get a link from us just add the following HTML to your site on a relevant page:
<a href="http://potassium_hydroxide.totallyexplained.com">Potassium hydroxide Totally Explained</a>
Then simply click through this link from your web page. Our crawlers will verify your link, extract the title of your web page and instantly add a link back to it. If you like you can remove the words Totally Explained and embed the link in article text.
As long as your link remains in place, we'll keep our link to you right here. Please play fair - our crawlers are watching. Your site must be closely related to this one's topic. Any kind of spamming, dubious practises or removing the link will result in your link from us being dropped and, potentially, your whole site being banned. |
