Lye

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Pellets of potash lye (potassium hydroxide) Potassium hydroxide.jpg
Pellets of potash lye (potassium hydroxide)
Pellets of soda lye (sodium hydroxide) SodiumHydroxide.jpg
Pellets of soda lye (sodium hydroxide)

A lye is an alkali metal hydroxide. Traditionally it was obtained by using rainwater to leach wood ashes, which are strongly alkaline and highly soluble in water, of their potassium hydroxide (KOH), producing lye water, a caustic basic solution. Then the lye water would either be used as such, as for curing olives before brining them, or evaporated of water to leave crystalline lye behind. [1] [2] "Lye" most accurately refers to sodium hydroxide (NaOH), but historically has been conflated to include other alkali materials, most notably potassium hydroxide.

Contents

Today, lye is commercially manufactured using a membrane cell chloralkali process. It is supplied in various forms such as flakes, pellets, microbeads, coarse powder or a solution. Lye has traditionally been used as a major ingredient in soapmaking.

Etymology

The English word lye /ˈlaɪ/ has cognates in all Germanic languages, and originally designated a bath or hot spring. [3]

Uses

Food

Lyes are used to cure many types of food, including the traditional Nordic lutefisk, olives (making them less bitter), canned mandarin oranges, hominy, lye rolls, century eggs, pretzels, candied pumpkins, and bagels. They are also used as a tenderizer in the crust of baked Cantonese moon cakes, in "zongzi" (glutinous rice dumplings wrapped in bamboo leaves), in chewy southern Chinese noodles popular in Hong Kong and southern China, and in Japanese ramen noodles. Lye provides the crisp glaze on hard pretzels. It's used in kutsinta, a type of rice cake from the Philippines together with pitsi-pitsî. [4] 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 corn by the tribes of the Eastern Woodlands in North America.

In the United States, food-grade lye must meet the requirements outlined in the Food Chemicals Codex (FCC), [5] as prescribed by the U.S. Food and Drug Administration (FDA). [6] Lower grades of lye that are unsuitable for use in food preparation are commonly used as drain cleaners and oven cleaners. [6] [ page needed ]

Soap

Both sodium hydroxide and potassium hydroxide are used in making 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, and then placed into a mold.

Household

Bottles of alkaline drain cleaners containing lye NaOH - drain-cleaner.jpg
Bottles of alkaline drain cleaners containing lye

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 grease-dissolving abilities. Lyes decompose greases via alkaline ester hydrolysis, yielding water-soluble 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, 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, [7] [8] [9] and the only solids that remain are very fragile bone hulls of mostly calcium phosphate, which can be mechanically crushed to a fine powder with very little force. [10] [11] Sodium hydroxide is frequently used in the process of decomposing roadkill dumped in landfills by animal disposal contractors. [8] Due to its low cost and easy availability, it has also been used to dispose of corpses by criminals. Italian serial killer Leonarda Cianciulli used this chemical to turn dead bodies into soap. [12] In Mexico, a man who worked for drug cartels admitted to having disposed of more than 300 bodies with it. [13]

Fungus identification

A 3–10% solution of potassium hydroxide (KOH) gives a color change in some species of mushrooms:

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. [14]

Protection

Personal protective equipment including safety glasses, chemical-resistant gloves, and adequate ventilation are required for the safe handling of lye. When in proximity to lye that is dissolving in an open container of water, the use of a vapor-resistant face mask is recommended. Adding lye too quickly can cause a runaway thermal reaction which can result in the mixture boiling or erupting.

Storage

Lye in its solid state is deliquescent and has a strong affinity for moisture in the air. As a result, lye will dissolve when exposed to open air, absorbing large amounts of atmospheric moisture. Accordingly, lye is stored in air-tight (and correspondingly moisture tight) containers. Glass is not a good material to be used for storage as severe alkalis 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, flesh, and the cornea. Solutions containing lyes can cause chemical burns, permanent injuries, scarring and blindness, immediately upon contact. Lyes may be harmful or even fatal if swallowed; ingestion can cause esophageal stricture. Moreover, the solvation of dry solid lye is highly exothermic and the resulting heat may cause additional burns or ignite flammables.

The reaction between sodium hydroxide and some metals is also hazardous. Aluminium, magnesium, zinc, tin, chromium, brass and bronze all react with lye to produce hydrogen gas. Since hydrogen is flammable, mixing a large quantity of lye with aluminium could result in an explosion. Both the potassium and sodium forms are able to dissolve copper.

See also

Related Research Articles

In chemistry, an alkali 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 soluble base has a pH greater than 7.0. The adjective alkaline, and less often, alkalescent, is commonly used in English as a synonym for basic, especially for bases soluble in water. This broad use of the term is likely to have come about because alkalis were the first bases known to obey the Arrhenius definition of a base, and they are still among the most common bases.

<span class="mw-page-title-main">Hydroxide</span> Chemical compound

Hydroxide is a diatomic anion with chemical formula OH−. It consists of an oxygen and hydrogen atom held together by a single covalent bond, and carries a negative electric charge. It is an important but usually minor constituent of water. It functions as a base, a ligand, a nucleophile, and a catalyst. The hydroxide ion forms salts, some of which dissociate in aqueous solution, liberating solvated hydroxide ions. Sodium hydroxide is a multi-million-ton per annum commodity chemical. The corresponding electrically neutral compound HO• is the hydroxyl radical. The corresponding covalently bound group –OH of atoms is the hydroxy group. Both the hydroxide ion and hydroxy group are nucleophiles and can act as catalysts in organic chemistry.

<span class="mw-page-title-main">Hominy</span> Dried nixtamalized corn consumed as food

Hominy is a food produced from dried maize (corn) kernels that have been treated with an alkali, in a process called nixtamalization. "Lye hominy" is a type of hominy made with lye.

Hydrolysis is any chemical reaction in which a molecule of water breaks one or more chemical bonds. The term is used broadly for substitution, elimination, and solvation reactions in which water is the nucleophile.

<span class="mw-page-title-main">Sodium hydroxide</span> Chemical compound with formula NaOH

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 Na+ and hydroxide anions OH−.

<span class="mw-page-title-main">Sodium carbonate</span> Chemical compound

Sodium carbonate is the inorganic compound with the formula Na2CO3 and its various hydrates. All forms are white, odourless, water-soluble salts that yield alkaline solutions in water. Historically, it was extracted from the ashes of plants grown in sodium-rich soils, and because the ashes of these sodium-rich plants were noticeably different from ashes of wood, sodium carbonate became known as "soda ash". It is produced in large quantities from sodium chloride and limestone by the Solvay process, as well as by carbonating sodium hydroxide which is made using the Chlor-alkali process.

<span class="mw-page-title-main">Potassium chloride</span> Ionic compound (KCl)

Potassium chloride is a metal halide salt composed of potassium and chlorine. It is odorless and has a white or colorless vitreous crystal appearance. The solid dissolves readily in water, and its solutions have a salt-like taste. Potassium chloride can be obtained from ancient dried lake deposits. KCl is used as a fertilizer, in medicine, in scientific applications, domestic water softeners, and in food processing, where it may be known as E number additive E508.

<span class="mw-page-title-main">Potassium hydroxide</span> Inorganic compound (KOH)

Potassium hydroxide is an inorganic compound with the formula KOH, and is commonly called caustic potash.

Saponification is a process of cleaving esters into carboxylate salts and alcohols by the action of aqueous alkali. Typically aqueous sodium hydroxide solutions are used. It is an important type of alkaline hydrolysis. When the carboxylate is long chain, its salt is called a soap. The saponification of ethyl acetate gives sodium acetate and ethanol:

<span class="mw-page-title-main">Potassium cyanide</span> Highly toxic crystalline salt

Potassium cyanide is a compound with the formula KCN. It is a colorless salt, similar in appearance to sugar, that is highly soluble in water. Most KCN is used in gold mining, organic synthesis, and electroplating. Smaller applications include jewellery for chemical gilding and buffing. Potassium cyanide is highly toxic, and a dose of 200 to 300 milligrams will kill nearly any human.

<span class="mw-page-title-main">Saponification value</span> Milligrams of a base required to saponify 1g of fat

Saponification value or saponification number represents the number of milligrams of potassium hydroxide (KOH) or sodium hydroxide (NaOH) required to saponify one gram of fat under the conditions specified. It is a measure of the average molecular weight of all the fatty acids present in the sample in form of triglycerides. The higher the saponification value, the lower the fatty acids average length, the lighter the mean molecular weight of triglycerides and vice versa. Practically, fats or oils with high saponification value are more suitable for soap making.

<span class="mw-page-title-main">Nixtamalization</span> Procedure for preparing corn to eat

Nixtamalization is a process for the preparation of maize, or other grain, in which the grain is soaked and cooked in an alkaline solution, usually limewater, washed, and then hulled. The term can also refer to the removal via an alkali process of the pericarp from other grains such as sorghum.

A relaxer is a type of lotion or cream generally used by people with tight curls or very curly hair which makes hair easier to straighten by chemically "relaxing" the natural curls. The active agent is usually a strong alkali, although some formulations are based on ammonium thioglycolate or formaldehyde.

<span class="mw-page-title-main">Electrolysed water</span> Chemical mixture in water solution

Electrolysed water is produced by the electrolysis of ordinary tap water containing dissolved sodium chloride. The electrolysis of such salt solutions produces a solution of hypochlorous acid and sodium hydroxide. The resulting water can be used as a disinfectant.

The alkali hydroxides are a class of chemical compounds which are composed of an alkali metal cation and the hydroxide anion. The alkali hydroxides are:

<span class="mw-page-title-main">Cleaning agent</span> Substance used to remove dirt or other contaminants

Cleaning agents or hard-surface cleaners are substances used to remove dirt, including dust, stains, foul odors, and clutter on surfaces. Purposes of cleaning agents include health, beauty, removing offensive odor, and avoiding the spread of dirt and contaminants to oneself and others. Some cleaning agents can kill bacteria and clean at the same time. Others, called degreasers, contain organic solvents to help dissolve oils and fats.

Potassium methoxide is the alkoxide of methanol with the counterion potassium and is used as a strong base and as a catalyst for transesterification, in particular for the production of biodiesel.

Saltwater soap, also called sailors' soap, is a potassium-based soap for use with seawater. Inexpensive common commercial soap will not lather or dissolve in seawater due to high levels of sodium chloride in the water. Similarly, common soap does not work as well as potassium-based soap in hard water where calcium replaces the sodium, making residual insoluble "scum" due to the insolubility of the soap residue. To be an effective cleaning agent, soap must be able to dissolve in water.

<span class="mw-page-title-main">Alkaline noodles</span> Type of pasta

Alkaline noodles, alkali noodles, or alkaline pasta is a variation of noodles with a much higher quantity of alkali than usual. The most common examples are Chinese lamian noodles and Japanese ramen noodles. The addition of alkali changes both the flavor and texture of the noodles, and makes them feel slippery in the mouth and on the fingers; they also develop a yellow color and are more elastic than ordinary noodles. Various flours such as ordinary all-purpose white flour, bread flour, and semolina flour can be used, with somewhat varying results. The yellow color is due to flavones that occur naturally in flour, which are normally colorless but turn yellow at alkaline pH.

Chemical drain cleaners or openers are pure or mixtures of chemicals used to unclog drains that are blocked by hair, food, or other organic materials. They are often accompanied by other mechanical drain cleaners for the optimal effect. Chemical drain cleaners are available through hardware stores, although some may be intended for use by licensed plumbers. They may contain either strong acids or strong alkalis. These cleaners contain chemicals that dissolve at least some of the material causing the clog.

References

  1. ↑ "How to make lye". wikiHow. 15 January 2024. Retrieved 24 January 2024.
  2. ↑ Garms, Gabe (9 December 2015). "Turning your wood ash into lye for soap making". Raven’s Roots Naturalist School. Retrieved 24 January 2024.
  3. ↑ Barnhart, Robert K. (1997). The Barnhart concise dictionary of etymology. New York: Harper-Collins. ISBN   978-0-06-270084-1.
  4. ↑ "Puto". Rice Recipes. Philippine Rice Research Institute. Archived from the original on 25 November 2014. Retrieved 15 January 2015.
  5. ↑ "Food Chemicals Codex".
  6. 1 2 "FD&C Act Chapter IV: Food". US Food and Drug Administration. 3 November 2018.
  7. ↑ Ayres, Chris (27 February 2010), "Clean green finish that sends a loved one down the drain", The Times, retrieved 20 February 2013
  8. 1 2 Thacker, H. Leon; Kastner, Justin (August 2004), "Chapter 6" (PDF), Carcass Disposal: A Comprehensive Review, National Agricultural Biosecurity Center, Kansas State University, archived from the original (PDF) on 6 February 2009, retrieved 8 March 2010
  9. ↑ Saqib Mukhtar; Frederick O. Boadu; Yanhong H. Jin; Won-Bo Shim; Tom A.Vestal; Cody L. Wilson (17 July 2009). "Managing Contaminated Animal and Plant Materials Field Guide on Best Practices" (PDF). Texas A&M Agrilife Extension Service. pp. 233–259. Retrieved 2 November 2014.
  10. ↑ Wilson, Joseph H. "The History of Alkaline Hydrolysis" (PDF). Joseph H. Wilson. Archived from the original (PDF) on 2 November 2014. Retrieved 2 November 2014.
  11. ↑ Roach, Mary (2004). Stiff: The Curious Lives of Human Cadavers. New York: W.W. Norton & Company. ISBN   0-393-32482-6.
  12. ↑ "Sodium: Getting rid of dirt - and murder victims". BBC News. 3 May 2014.
  13. ↑ Booth, William (January 27, 2009). "'Stewmaker' Stirs Horror in Mexico". Washington Post .
  14. ↑ "Canadian Centre for Occupational Health and Safety". CCOHS. 20 May 2022.

Further reading

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