![SodiumHydroxide](https://upload.wikimedia.org/wikipedia/commons/3/34/SodiumHydroxide.jpg)
A lye is a
metal hydroxide Metal hydroxides are hydroxides of metals. They are often strong bases. They consist of hydroxide anions and metallic cations. Some metal hydroxides, such as alkali metal hydroxides, ionize completely when dissolved. Certain metal hydroxides ar ...
traditionally obtained by
leaching
Leaching is the loss or extraction of certain materials from a carrier into a liquid (usually, but not always a solvent). and may refer to:
* Leaching (agriculture), the loss of water-soluble plant nutrients from the soil; or applying a small amou ...
wood ashes, or a strong
alkali
In chemistry, an alkali (; from ar, القلوي, al-qaly, lit=ashes of the saltwort) is a basic, ionic salt of an alkali metal or an alkaline earth metal. An alkali can also be defined as a base that dissolves in water. A solution of a ...
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 ''caus ...
basic
BASIC (Beginners' All-purpose Symbolic Instruction Code) is a family of general-purpose, high-level programming languages designed for ease of use. The original version was created by John G. Kemeny and Thomas E. Kurtz at Dartmouth College ...
solutions. "Lye" most commonly refers to
sodium hydroxide
Sodium hydroxide, also known as lye and caustic soda, is an inorganic compound with the formula NaOH. It is a white solid ionic compound consisting of sodium cations and hydroxide anions .
Sodium hydroxide is a highly caustic base and alkali ...
(NaOH), but historically has been used for
potassium hydroxide
Potassium hydroxide is an inorganic compound with the formula K OH, and is commonly called caustic potash.
Along with sodium hydroxide (NaOH), KOH is a prototypical strong base. It has many industrial and niche applications, most of which exp ...
(KOH).
Today, lye is commercially manufactured using a
membrane cell
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. Membranes can be generally classified into synthetic membranes and biological membranes. Bi ...
chloralkali process
The chloralkali process (also chlor-alkali and chlor alkali) is an industrial process for the electrolysis of sodium chloride (NaCl) solutions. It is the technology used to produce chlorine and sodium hydroxide (caustic soda), which are comm ...
. It is supplied in various forms such as flakes, pellets, microbeads, coarse powder or a
solution
Solution may refer to:
* Solution (chemistry), a mixture where one substance is dissolved in another
* Solution (equation), in mathematics
** Numerical solution, in numerical analysis, approximate solutions within specified error bounds
* Soluti ...
. Lye has traditionally been used as a major ingredient in soapmaking.
Etymology
The English word has cognates in all
Germanic languages
The Germanic languages are a branch of the Indo-European language family spoken natively by a population of about 515 million people mainly in Europe, North America, Oceania and Southern Africa. The most widely spoken Germanic language, Engli ...
, 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 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 cured. The ...
many types of food, including the traditional Nordic
lutefisk
''Lutefisk'' (Norwegian, in Northern and parts of Central Norway, in Southern Norway; sv, lutfisk ; fi, lipeäkala ; literally "lye fish") is dried whitefish (normally cod, but ling and burbot are also used). It is made from aged stockfi ...
,
olive
The olive, botanical name ''Olea europaea'', meaning 'European olive' in Latin, is a species of small tree or shrub in the family Oleaceae, found traditionally in the Mediterranean Basin. When in shrub form, it is known as ''Olea europaea'' ...
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, it is usually eaten plain or in fruit salads. Tangerines are a group of orange-coloured ...
s,
hominy
Hominy (Spanish: maÃz molido; literally meaning "milled corn") is a food produced from dried maize (corn) kernels that have been treated with an alkali, in a process called nixtamalization ( is the Nahuatl word for "hominy"). "Lye hominy" is a ...
,
lye roll
Lye rolls are a baked specialty in Germany (especially in Bavaria and Swabia), France (Alsace), Austria, and Switzerland. They are made by immersing bread rolls in a lye solution before baking. The German name is ''Laugengebäck'' for any baked ...
s,
century egg
Century eggs (), also known under a wide variety of names (see infobox), are a Chinese egg-based culinary dish made by preserving duck, chicken or quail eggs in a mixture of clay, ash, salt, quicklime, and rice hulls for several weeks to severa ...
s,
pretzel
A pretzel (), from German pronunciation, standard german: Breze(l) ( and French / Alsatian: ''Bretzel'') is a type of baked bread made from dough that is commonly shaped into a knot. The traditional pretzel shape is a distinctive symmetrical ...
s, and
bagel
A bagel ( yi, בײגל, translit=beygl; pl, bajgiel; also spelled beigel) is a bread roll originating in the Jewish communities of Poland. It is traditionally shaped by hand into a roughly hand-sized ring from yeasted wheat dough that is first ...
s. They are also used as a tenderizer in the crust of baked Cantonese
moon cakes, in "
zongzi
''Zongzi'' (; ), ''rouzong'' () or simply ''zong'' (Cantonese Jyutping: ''zung2'') is a traditional Chinese rice dish made of glutinous rice stuffed with different fillings and wrapped in bamboo leaves (generally of the species ''Indocalamus t ...
" (
glutinous rice
Glutinous rice (''Oryza sativa var. glutinosa''; also called sticky rice, sweet rice or waxy rice) is a type of rice grown mainly in Southeast and East Asia, and the northeastern regions of South Asia, which has opaque grains, very low amylose ...
dumplings wrapped in bamboo leaves), in chewy southern
Chinese noodles
Chinese noodles vary widely according to the region of production, ingredients, shape or width, and manner of preparation. Noodles were invented in China, and are an essential ingredient and staple in Chinese cuisine. They are an important part ...
popular in Hong Kong and southern China, and in Japanese
ramen noodles
is a Japanese noodle dish. It consists of served in a broth; common flavors are soy sauce and miso, with typical toppings including , nori (dried seaweed), menma (bamboo shoots), and scallions. Ramen has its roots in Chinese noodle dishes. ...
. They are also used in
kutsinta
''Puto cuchinta'' or ''kutsinta'' is a type of Steaming, steamed rice cake (''Puto (food), puto'') found throughout the Philippines. It is made from a mixture of tapioca or rice flour, brown sugar and lye, enhanced with yellow food coloring or An ...
, a type of rice cake from the Philippines together with
pitsi-pitsî
Pichi-pichi, also spelled pitsi-pitsi, is a Filipino dessert made from steamed cassava flour balls mixed with sugar and lye. It is also commonly flavored with pandan leaves. It is served rolled in freshly grated coconut, cheese, or latik (cocon ...
.
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 (Spanish: maÃz molido; literally meaning "milled corn") is a food produced from dried maize (corn) kernels that have been treated with an alkali, in a process called nixtamalization ( is the Nahuatl word for "hominy"). "Lye hominy" is a ...
corn by the tribes of the Eastern Woodlands in
North America
North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...
.
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 primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...
, food-grade lye must meet the requirements outlined in the
Food Chemicals Codex The Food Chemicals Codex (FCC) is a collection of internationally recognized standards for the purity and identity of food ingredients.
Scope
The FCC features more than 1,250 monographs, including food-grade chemicals, processing aids, foods (suc ...
(FCC), as prescribed by the
U.S. Food and Drug Administration
The United States Food and Drug Administration (FDA or US FDA) is a federal agency of the Department of Health and Human Services. The FDA is responsible for protecting and promoting public health through the control and supervision of food ...
(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 salt of a fatty acid used in a variety of cleansing and lubricating products. In a domestic setting, soaps are surfactants usually used for washing, bathing, and other types of housekeeping. In industrial settings, soaps are use ...
. 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 but sometimes used generically in the English-speaking world), is a countertop electrical cooking appliance used to simmer at a lower temperature than othe ...
, and then placed into a mold.
Household
![NaOH - drain-cleaner](https://upload.wikimedia.org/wikipedia/commons/3/31/NaOH_-_drain-cleaner.jpg)
Lyes are also valued for their cleaning effects. Sodium hydroxide is commonly the major constituent in commercial and industrial
oven cleaner
Cleaning agents or hard-surface cleaners are substances (usually liquids, powders, sprays, or granules) used to remove dirt, including dust, stains, bad smells, and clutter on surfaces. Purposes of cleaning agents include health, beauty, removing ...
s and clogged
drain opener
A drain cleaner is method for unblocking sewer pipes or clogged wastewater drains. The term may also refer to a mechanical device such as a plumber's snake, drain auger, toilet plunger, or similar device. Occasionally, the term is applied to a plu ...
s, due to its
grease-dissolving abilities. Lyes decompose greases via
alkaline ester hydrolysis, yielding
water-soluble
In chemistry, solubility is the ability of a substance, the solute, to form a solution with another substance, the solvent. Insolubility is the opposite property, the inability of the solute to form such a solution.
The extent of the solub ...
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 is a hydroxide ion.
Example
In the alkaline hydrolysis of esters and amides the hydroxide ion nucleophi ...
, the process involves placing the animal carcass 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
The term calcium phosphate refers to a family of materials and minerals containing calcium ions (Ca2+) together with inorganic phosphate anions. Some so-called calcium phosphates contain oxide and hydroxide as well. Calcium phosphates are white ...
, which can be mechanically crushed to a fine powder with very little force.
Sodium hydroxide is frequently used in the process of decomposing
roadkill
Roadkill is an animal or animals that have been struck and killed by drivers of motor vehicles on highways. Wildlife-vehicle collisions (WVC) have increasingly been the topic of academic research to understand the causes, and how it can be mi ...
dumped in landfills by animal disposal contractors.
Due to its low cost and easy availability, it has also been used to dispose of corpses by criminals.
Italian
Italian(s) may refer to:
* Anything of, from, or related to the people of Italy over the centuries
** Italians, an ethnic group or simply a citizen of the Italian Republic or Italian Kingdom
** Italian language, a Romance language
*** Regional Ita ...
serial killer
A serial killer is typically a person who murders three or more persons,A
*
*
*
* with the murders taking place over more than a month and including a significant period of time between them. While most authorities set a threshold of three ...
Leonarda Cianciulli
Leonarda Cianciulli (18 April 1894 – 15 October 1970) was an Italian serial killer. Better known as the Soap-Maker of Correggio (Italian: ''la Saponificatrice di Correggio''), she murdered three women in the town of Correggio, Reggio Emilia, in ...
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 with the formula K OH, and is commonly called caustic potash.
Along with sodium hydroxide (NaOH), KOH is a prototypical strong base. It has many industrial and niche applications, most of which exp ...
(KOH) gives a color change in some species of mushrooms:
* In ''
Agaricus
''Agaricus'' is a genus of mushrooms containing both edible and poisonous species, with over 400 members worldwide and possibly again as many disputed or newly-discovered species. The genus includes the common ("button") mushroom (''Agaricus bisp ...
'', some species such as
A. xanthodermus turn yellow with KOH, many have no reaction, and ''
A. subrutilescens'' turns green.
* Distinctive change occurs for some species of ''
Cortinarius
''Cortinarius'' is a globally distributed genus of mushrooms in the family Cortinariaceae. It is suspected to be the largest genus of agarics, containing over 2,000 widespread species. A common feature among all species in the genus ''Cortinariu ...
'' and
boletes
{{refimprove, date=July 2020
A bolete is a type of mushroom, or fungal fruiting body. It can be identified thanks to a unique mushroom cap. The cap is clearly different from the stem. On the underside of the cap there is usually a spongy surfa ...
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, helmets, goggles, or other garments or equipment designed to protect the wearer's body from injury or infection. The hazards addressed by protective equipment include physical, elec ...
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 or adsorption from the surrounding environment, which is usually at normal or room temperature. If water molecules become suspended among the substance ...
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 tissues; 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 diffe ...
,
flesh
Flesh is any aggregation of soft tissues of an organism. Various multicellular organisms have soft tissues that may be called "flesh". In mammals, including humans, ''flesh'' encompasses muscle
Skeletal muscles (commonly referred to as mu ...
, and the
cornea
The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber. Along with the anterior chamber and lens, the cornea refracts light, accounting for approximately two-thirds of the eye's total optical power ...
. 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, base or oxidizer) or a cytotoxic agent (such as mustard gas, lewisite or arsine). Chemical burns follow standard burn classification and may ca ...
s, permanent injuries, scarring and
blindness
Visual impairment, also known as vision impairment, is a medical definition primarily measured based on an individual's better eye visual acuity; in the absence of treatment such as correctable eyewear, assistive devices, and medical treatment†...
, 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 that causes swallowing difficulties.
Signs and symptoms
Symptoms of esophageal strictures include heartburn, bitter or acid taste in the mouth, chok ...
. Moreover, the
solvation
Solvation (or dissolution) describes the interaction of a solvent with dissolved molecules. Both ionized and uncharged molecules interact strongly with a solvent, and the strength and nature of this interaction influence many properties of the ...
of dry
solid
Solid is one of the State of matter#Four fundamental states, four fundamental states of matter (the others being liquid, gas, and Plasma (physics), plasma). The molecules in a solid are closely packed together and contain the least amount o ...
lyes is highly
exothermic
In thermodynamics, an exothermic process () is a thermodynamic process or reaction that releases energy from the system to its surroundings, usually in the form of heat, but also in a form of light (e.g. a spark, flame, or flash), electricity (e ...
; the resulting
heat
In thermodynamics, heat is defined as the form of energy crossing the boundary of a thermodynamic system by virtue of a temperature difference across the boundary. A thermodynamic system does not ''contain'' heat. Nevertheless, the term is al ...
may cause additional burns or ignite flammables.
The reaction between sodium hydroxide and a few metals is also hazardous.
Aluminium
Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. I ...
reacts with lyes to produce
hydrogen
Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic, an ...
gas. Since hydrogen is
flammable
A combustible material is something that can burn (i.e., ''combust'') in air. A combustible material is flammable if it ignites easily at ambient temperatures. In other words, a combustible material ignites with some effort and a flammable mat ...
, 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 with the symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 of the periodic ta ...
,
zinc
Zinc is a chemical element with the symbol Zn and atomic number 30. Zinc is a slightly brittle metal at room temperature and has a shiny-greyish appearance when oxidation is removed. It is the first element in group 12 (IIB) of the periodi ...
,
tin
Tin is a chemical element with the symbol Sn (from la, stannum) and atomic number 50. Tin is a silvery-coloured metal.
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, t ...
,
chromium
Chromium is a chemical element with the symbol Cr and atomic number 24. It is the first element in group 6. It is a steely-grey, lustrous, hard, and brittle transition metal.
Chromium metal is valued for its high corrosion resistance and hardne ...
,
brass
Brass is an alloy of copper (Cu) and zinc (Zn), in proportions which can be varied to achieve different mechanical, electrical, and chemical properties. It is a substitutional alloy: atoms of the two constituents may replace each other with ...
or
bronze
Bronze is an alloy consisting primarily of copper, commonly with about 12–12.5% tin and often with the addition of other metals (including aluminium, manganese, nickel, or zinc) and sometimes non-metals, such as phosphorus, or metalloids such ...
—producing hydrogen gas. Both the potassium and sodium forms are able to dissolve copper.
See also
*
Slaked lime
Calcium hydroxide (traditionally called slaked lime) is an inorganic compound with the chemical formula Ca( OH)2. It is a colorless crystal or white powder and is produced when quicklime (calcium oxide) is mixed or slaked with water. It has ma ...
(calcium hydroxide)
References
Further reading
*
External links
*
*
{{Authority control
Hydroxides
Household chemicals
Deliquescent substances
Desiccants
Soaps
Sodium compounds