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A lye is a
metal hydroxideMetal hydroxides are hydroxides of metals. They are often strong base (chemistry), bases. They consist of hydroxide anions and metallic cations. Some metal hydroxides, such as alkali metal hydroxides, ionize completely when dissolved. Certain meta ...
traditionally obtained by leaching wood ashes, or a strong
alkali In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science that covers the Chemical element, elements that make up matter to the chemical compound, compounds composed of ato ...

alkali
which is highly soluble in water producing
caustic Caustic most commonly refers to: * Causticity, a property of various corrosive substances ** Sodium hydroxide, sometimes called ''caustic soda'' ** Potassium hydroxide, sometimes called ''caustic potash'' ** Calcium oxide, sometimes called ''caustic ...

caustic
basic Basic or BASIC may refer to: Science and technology * BASIC BASIC (Beginners' All-purpose Symbolic Instruction Code) is a family of General-purpose programming language, general-purpose, high-level programming languages whose design philosophy ...
solutions. "Lye" most commonly refers to
sodium hydroxide Sodium hydroxide, also known as lye A lye is a metal hydroxide traditionally obtained by leaching wood ashes, or a strong alkali In chemistry Chemistry is the scientific discipline involved with Chemical element, elements and chem ...

sodium hydroxide
(NaOH), but historically has been used for
potassium hydroxide Potassium hydroxide is an inorganic compound In chemistry, an inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds, that is, a compound that is not an organic compound. However, the distinction is not clearly defi ...

potassium hydroxide
(KOH). Today, lye is commercially manufactured using a
membrane cell Image:Schematic size.jpg, up150px, Schematic of size-based membrane exclusion A membrane is a selective barrier; it allows some things to pass through but stops others. Such things may be molecules, ions, or other small particles. Biological membr ...
chloralkali process The chloralkali process (also chlor-alkali and chlor alkali In chemistry Chemistry is the scientific discipline involved with Chemical element, elements and chemical compound, compounds composed of atoms, molecules and ions: their compo ...
. It is supplied in various forms such as flakes, pellets, microbeads, coarse powder or a
solution Solution may refer to: * Solution (chemistry) Image:SaltInWaterSolutionLiquid.jpg, upMaking a saline water solution by dissolving Salt, table salt (sodium chloride, NaCl) in water. The salt is the solute and the water the solvent. In chemistry ...
. Lye has traditionally been used as a major ingredient in soap making.


Etymology

The English word "lye" has cognates in all
Germanic languages The Germanic languages are a branch of the Indo-European The Indo-European languages are a language family native to western and southern Eurasia. It comprises most of the languages of Europe together with those of the northern Indian sub ...

Germanic languages
, and originally designated a bath or hot spring.


Uses


Food

Lyes are used to
cure A cure is a substance or procedure that ends a medical condition, such as a medication, a surgery, surgical operation, a change in lifestyle or even a philosophical mindset that helps end a person's sufferings; or the state of being healed, or cur ...
many types of food, including the traditional Nordic
lutefisk ''Lutefisk'' (Norwegian Norwegian, Norwayan, or Norsk may refer to: *Something of, from, or related to Norway, a country in northwestern Europe *Norwegians, both a nation and an ethnic group native to Norway *Demographics of Norway *The Norweg ...

lutefisk
,
olive The olive, botanical name ''Olea europaea'', meaning "European olive", is a species In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemica ...

olive
s (making them less bitter), canned
mandarin orange The mandarin orange (''Citrus reticulata''), also known as the mandarin or mandarine, is a small citrus tree fruit. Treated as a distinct species of Orange (fruit), orange, it is usually eaten plain or in fruit salads. Tangerines are a group of o ...
s,
hominy Hominy is a food produced from dried maize (corn) kernels that have been treated with an alkali, in a process called nixtamalization ( is the Nahuatl Nahuatl (; )The Classical Nahuatl word (noun stem ''nāhua'', + absolutive ''-tl'' ) is ...
,
lye roll Lye rolls are a baked specialty in Germany ) , image_map = , map_caption = , map_width = 250px , capital = Berlin , coordinates = , largest_city = capital , languages_type = Official language , languages = German language, Germa ...
s,
century egg Century eggs (), also known as preserved eggs, hundred-year eggs, thousand-year eggs, thousand-year-old eggs, millennium eggs, skin eggs, or black eggs, are a Chinese Chinese can refer to: * Something related to China China, officially ...

century egg
s,
pretzel A pretzel (), from dialectal German pronunciation, standard german: Breze(l) ( and French language, French / Alsatian dialect, Alsatian: ''Bretzel'') is a type of baking, baked pastry made from dough that is commonly shaped into a knot. The tradi ...

pretzel
s,
bagel A bagel ( yi, בײגל '; pl, bajgiel), also historically spelled beigel, is a bread product originating in the Jewish communities Jewish ethnic divisions refer to many distinctive communities within the world's Ethnicity, ethnically Jewis ...

bagel
s, and the traditional Turkish pumpkin dessert
Kabak tatlısı
Kabak tatlısı
(creating a hard crust while the inside remains soft). They are also used as a tenderizer in the crust of baked Cantonese
moon cakes
moon cakes
, in "
zongzi ''Zongzi'' (; ) or simply ''zong'' (Cantonese : ''zung2'') is a traditional Chinese rice dish made of stuffed with different fillings and wrapped in leaves (generally of the species '), or sometimes with or other large flat leaves. They are ...

zongzi
" (
glutinous rice Glutinous rice (''Oryza sativa ''Oryza sativa'', common name, commonly known as Asian rice, is the plant species most commonly referred to in English as rice. It is the List of rice cultivars, type of farmed rice whose cultivars are most com ...

glutinous rice
dumplings wrapped in bamboo leaves), in chewy southern
Chinese noodles Noodles are an essential ingredient and Staple food, staple in Chinese cuisine. Chinese noodles vary widely according to the region of production, ingredients, shape or width, and manner of preparation. They are an important part of most regional ...
popular in Hong Kong and southern China, and in Japanese
ramen noodles (literally: "pulled noodles") is a Japanese noodle soup. It consists of Chinese noodles, Chinese wheat noodles served in a meat or (occasionally) fish-based broth, often flavored with soy sauce or miso, and uses toppings such as , nori (dried ...
. They are also used in
kutsinta ''Puto cuchinta'' or ''kutsinta'' is a type of steamed Steaming is a method of cooking using steam. This is often done with a food steamer, a kitchen appliance made specifically to cook food with steam, but food can also be steamed in a wok. In t ...
, a type of rice cake from the Philippines together with pitsi-pitsî. In Assam, north east India, extensive use is made of a type of lye called khar in Assamese and karwi in Boro which is obtained by filtering the ashes of various banana stems, roots and skin in their cooking and also for curing, as medicine and as a substitute for soap. Lye made out of wood ashes is also used in the nixtamalization process of
hominy Hominy is a food produced from dried maize (corn) kernels that have been treated with an alkali, in a process called nixtamalization ( is the Nahuatl Nahuatl (; )The Classical Nahuatl word (noun stem ''nāhua'', + absolutive ''-tl'' ) is ...
corn by the tribes of the Eastern Woodlands in
North America North America is a continent A continent is any of several large landmasses. Generally identified by convention (norm), convention rather than any strict criteria, up to seven geographical regions are commonly regarded as continen ...

North America
. In the
United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country in . It consists of 50 , a , five major , 326 , and some . At , it is the world's . The United States shares significan ...

United States
, food-grade lye must meet the requirements outlined in the Food Chemicals Codex (FCC), as prescribed by the
U.S. Food and Drug Administration The United States of America (USA), commonly known as the United States (U.S. or US), or America, is a country primarily located in North America North America is a continent entirely within the Northern Hemisphere and almost all ...

U.S. Food and Drug Administration
(FDA). Lower grades of lye that are unsuitable for use in food preparation are commonly used as drain de-cloggers and oven cleaners.


Soap

Lye in the form of both sodium hydroxide and potassium hydroxide is used in making
soap Soap is a of a used in a variety of cleansing and lubricating products. In a domestic setting, soaps are s usually used for , , and other types of . In industrial settings, soaps are used as s, components of some s, and precursors to s. Wh ...

soap
. Potassium hydroxide soaps are softer and more easily dissolved in water than sodium hydroxide soaps. Sodium hydroxide and potassium hydroxide are not interchangeable in either the proportions required or the properties produced in making soaps. "Hot process" soap making also uses lye as the main ingredient. Lye is added to water, cooled for a few minutes and then added to oils and butters. The mixture is then cooked over a period of time (1–2 hours), typically in a
slow cooker A slow cooker, also known as a crock-pot (after a trademark owned by Sunbeam Products Sunbeam Products is an American brand that has produced electric home appliances since 1910. Its products have included the Mixmaster mixer, the Sunbeam ...
, and then placed into a mold.


Household

Lyes are also valued for their cleaning effects. Sodium hydroxide is commonly the major constituent in commercial and industrial oven cleaners and clogged drain openers, due to its -dissolving abilities. Lyes decompose greases via , yielding
water-soluble In chemistry, solubility is ability of a chemical substance, substance, the solute, to form a solution (chemistry), solution with another substance, the solvent. Insolubility is the opposite property, the inability of the solute to form such a ...
residues that are easily removed by rinsing.


Tissue digestion

Sodium or potassium hydroxide can be used to digest tissues of animal carcasses. Often referred to as
alkaline hydrolysis Alkaline hydrolysis, in organic chemistry, usually refers to types of nucleophilic substitution reactions in which the attacking nucleophile In chemistry, a nucleophile is a chemical species that forms bonds with Electrophile, electrophiles by do ...
, the process involves placing the carcass or body into a sealed chamber, adding a mixture of lye and water and the application of heat to accelerate the process. After several hours the chamber will contain a liquid with coffee-like appearance, and the only solids that remain are very fragile bone hulls of mostly
calcium phosphate Calcium phosphate is a family of materials and mineral In geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is an Earth science concerned with the solid Earth, the rock ...
, which can be mechanically crushed to a fine powder with very little force. Sodium hydroxide is frequently used in the process of decomposing
roadkill s like this bear are particularly vulnerable to becoming roadkill Roadkill is an Fauna, animal or animals that have been struck and killed by motor vehicle Electric bicycles parked in Yangzhou's main street, Wenchang Lu. They are a very commo ...

roadkill
dumped in landfills by animal disposal contractors. Due to its low cost and high availability, it has also been used to dispose of corpses by criminals.
Italian Italian may refer to: * Anything of, from, or related to the country and nation of Italy ** Italians, an ethnic group or simply a citizen of the Italian Republic ** Italian language, a Romance language *** Regional Italian, regional variants of the ...

Italian
serial killer A serial killer is typically a person who murders three or more people,A serial killer is most commonly defined as a person who kills three or more people for psychological gratification; reliable sources over the years agree. See, for example: ...
used this chemical to turn dead bodies into soap. In Mexico, a man who worked for drug cartels admitted to having disposed of more than 300 bodies with it.


Fungus identification

A 3–10% solution of
potassium hydroxide Potassium hydroxide is an inorganic compound In chemistry, an inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds, that is, a compound that is not an organic compound. However, the distinction is not clearly defi ...

potassium hydroxide
(KOH) gives a color change in some species of mushrooms: * In ''
Agaricus ''Agaricus'' is a genus Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. ...

Agaricus
'', some species such as turn yellow with KOH, many have no reaction, and '''' turns green. * Distinctive change occurs for some species of ''
Cortinarius ''Cortinarius'' is a globally distributed genus Genus (plural genera) is a taxonomic rank Taxonomy (general) is the practice and science of classification of things or concepts, including the principles that underlie such classification. The ...
'' and
boletes {{refimprove, date=July 2020 A bolete is a type of mushroom, or fungus, fungal fruiting body. It can be identified thanks to a unique mushroom pileus (mycology), cap. The cap is clearly different from the stipe (mycology), stem. On the underside ...


Safety


First aid

Sources recommend immediate removal of contaminated clothing/materials, gently brushing/wiping excess off of skin, and then flushing the area of exposure with running water for 15–60 minutes while contacting emergency services.


Protection

Personal protective equipment Personal protective equipment (PPE) is protective clothing A kanga, worn throughout the African Great Lakes region Clothing (also known as clothes, apparel, and attire) are items worn on the body. Typically, clothing is made of fabr ...
including safety glasses, chemical-resistant gloves, and adequate ventilation are required for the safe handling of lyes. When in proximity to a lye that is dissolving in an open container of water, the use of a vapor-resistant face mask is recommended. Adding lye to water too quickly can cause the solution to boil.


Storage

Solid lyes are
deliquescent Hygroscopy is the phenomenon of attracting and holding water molecules via either absorption (chemistry), absorption or adsorption from the surrounding Natural environment, environment, which is usually at normal or room temperature. If water m ...
s and have a strong affinity for air moisture. Solid lyes will deliquesce or dissolve when exposed to open air, absorbing a relatively large amount of water vapour. Accordingly, lyes are stored in air-tight plastic containers. Glass is not a good material to be used for storage as lyes are mildly corrosive to it. Similar to the case of other corrosives, the containers should be labeled to indicate the potential danger of the contents and stored away from children, pets, heat, and moisture.


Hazardous reactions

The majority of safety concerns with lye are also common with most corrosives, such as their potentially destructive effects on
living tissue In biology, tissue is a Biological organisation#Levels, biological organizational level between cell (biology), cells and a complete organ (biology), organ. A tissue is an ensemble of similar cells and their extracellular matrix from the same or ...
s; examples are the
skin Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: protection, regulation, and sensation. Other cuticle, animal coverings, such as the arthropod exoskeleton, have differ ...

skin
,
flesh Flesh is any aggregation of soft tissue Tissue may refer to: Biology * Tissue (biology), an ensemble of similar cells that together carry out a specific function * ''Triphosa haesitata'', a species of geometer moth found in North America * ''Tri ...

flesh
, and the
cornea The cornea is the transparent Transparency, transparence or transparent most often refer to transparency and translucency, the physical property of allowing the transmission of light through a material. They may also refer to: Literal uses * ...

cornea
. Solutions containing lyes can cause
chemical burn A chemical burn occurs when living tissue is exposed to a corrosive substance (such as a strong acid An acid is a molecule or ion capable of donating a proton (hydrogen ion H+) (a Brønsted–Lowry acid–base theory, Brønsted–Lowry acid ...
s, permanent injuries, scarring and
blindness Visual impairment, also known as vision impairment or vision loss, is a decreased ability to see to a degree that causes problems not fixable by usual means, such as glasses Glasses, also known as eyeglasses or spectacles, are vision eyew ...
, immediately upon contact. Lyes may be harmful or even fatal if swallowed; ingestion can cause
esophageal stricture A benign esophageal stricture, or peptic stricture, is a narrowing or tightening of the esophagus The esophagus (American English) or oesophagus (British English; American and British English spelling differences#ae and oe, see spelling diffe ...
. Moreover, the
solvation Solvation (or dissolution) describes the interaction of solvent A solvent (from the Latin language, Latin ''wikt:solvo#Latin, solvō'', "loosen, untie, solve") is a substance that dissolves a solute, resulting in a solution. A solvent is usual ...

solvation
of dry
solid Solid is one of the four fundamental states of matter (the others being liquid A liquid is a nearly incompressible fluid In physics, a fluid is a substance that continually Deformation (mechanics), deforms (flows) under an applied ...

solid
lyes is highly
exothermic In thermodynamics Thermodynamics is a branch of physics that deals with heat, Work (thermodynamics), work, and temperature, and their relation to energy, entropy, and the physical properties of matter and radiation. The behavior of these qu ...

exothermic
; the resulting
heat In thermodynamics Thermodynamics is a branch of physics that deals with heat, Work (thermodynamics), work, and temperature, and their relation to energy, entropy, and the physical properties of matter and radiation. The behavior of these ...

heat
may cause additional burns or ignite flammables. The reaction between sodium hydroxide and a few metals is also hazardous.
Aluminium Aluminium (aluminum in and ) is a with the  Al and  13. Aluminium has a density lower than those of other common , at approximately one third that of . It has a great affinity towards , and of on the surface when exposed to air ...

Aluminium
reacts with lyes to produce
hydrogen Hydrogen is the chemical element with the Symbol (chemistry), symbol H and atomic number 1. Hydrogen is the lightest element. At standard temperature and pressure, standard conditions hydrogen is a gas of diatomic molecules having the che ...

hydrogen
gas. Since hydrogen is
flammable , Germany ) , image_map = , map_caption = , map_width = 250px , capital = Berlin , coordinates = , largest_city = capital , languages_type = Official language , languages = German language, German , demonym = Germans, German , g ...
, mixing a large quantity of a lye such as sodium hydroxide with aluminium in a closed container is dangerous—especially when the system is at a high temperature, which speeds up the reaction. In addition to aluminium, lyes may also react with
magnesium Magnesium is a chemical element upright=1.0, 500px, The chemical elements ordered by link=Periodic table In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science ...

magnesium
,
zinc Zinc is a chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the chemical elements In chemistry, an element is a pure substance consisting only of atoms that all have the same numbe ...

zinc
,
tin Tin is a with the Sn (from la, ) and  50. Tin is a silvery-colored metal that characteristically has a faint yellow hue. Tin is soft enough to be cut with little force and a bar of tin can be bent by hand with little effort. When bent ...

tin
,
chromium Chromium is a chemical element upright=1.0, 500px, The chemical elements ordered by link=Periodic table In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science tha ...

chromium
,
brass Brass is an alloy An alloy is an admixture of metal A metal (from Ancient Greek, Greek μέταλλον ''métallon'', "mine, quarry, metal") is a material that, when freshly prepared, polished, or fractured, shows a lustrous appea ...

brass
or
bronze Bronze is an alloy An alloy is an admixture of metal A metal (from Ancient Greek, Greek μέταλλον ''métallon'', "mine, quarry, metal") is a material that, when freshly prepared, polished, or fractured, shows a lustrous appear ...

bronze
—producing hydrogen gas. Both the potassium and sodium forms are able to dissolve copper.


References


Further reading

*


See also

*
Slaked lime Calcium hydroxide (traditionally called slaked lime) is an inorganic compound In chemistry Chemistry is the scientific discipline involved with Chemical element, elements and chemical compound, compounds composed of atoms, molecules and ion ...
(calcium hydroxide)


External links

* * {{Authority control Hydroxides Household chemicals Deliquescent substances Desiccants Soaps Sodium compounds