AskDefine | Define lye

Dictionary Definition

lye n : a strong solution of sodium or potassium hydroxide

User Contributed Dictionary



  • /laɪ/
  • Rhymes with: -aɪ



  1. A strong caustic alkaline solution of potassium or sodium salts, obtained by leaching wood ashes. It is much used in making soap as well as its use in biodiesel.


a strong caustic alkaline solution of potassium or sodium salts
  • Danish: lud
  • Finnish: lipeä
  • Hungarian: lúg
  • Spanish: lejía
  • Swedish: lut
  • Polish: ług


  1. obsolete spelling of lie

Extensive Definition

Lye is a corrosive alkaline substance, commonly, sodium hydroxide (NaOH). Previously, lye was among the many different alkalis leached from hardwood ashes. In modern day, lye is commercially manufactured using a membrane cell method, which is an improvement from the previous diaphragm cell methods of Castner-Kellner, Gibbs, and Nelson.
Solid dry lye is commonly available as flakes, pellets, microbeads, and coarse powder. It is also available as solution, often dissolved in water. Lye is valued for its use in food preparation, soap making, biodiesel production, and household uses, such as oven cleaner and drain opener. thumb|Canister of solid dry lye.
Lye is being considered for dissolving the tissue of deceased human bodies as an environmentally-friendly alternative to cremation.

Food Uses

Lye is used to cure many types of food, such as: lutefisk, green olives, hominy, lye rolls, century eggs, pretzels, and Chinese noodles. In the United States food-grade lye must meet the requirements outlined in the Food Chemicals Codex (FCC), as prescribed by the US Food and Drug Administration (FDA). Lower grades of lye are commonly used as drain openers and oven cleaners and should not be used for food preparation.


Both solid dry lye and lye solutions are corrosive and will degrade organic tissue.

Hazardous Reactions

Solid sodium hydroxide or solutions containing high concentrations of sodium hydroxide may cause chemical burns, permanent injury or scarring, and blindness. Lye (sodium hydroxide) may be harmful or fatal if swallowed. Lye also has some medical properties when absorbed through the skin, discovered by the ancient Egyptians.
Solvation of sodium hydroxide is highly exothermic, and the resulting heat may cause heat burns or ignite flammables.
Avoid all contact with organic tissue (including human skin, eyes, mouth, and animals or pets). Keep away from clothing. Avoid all contact with aluminium.
The combination of aluminium and sodium hydroxide results in a large production of hydrogen gas: 2Al(s) + 6NaOH(aq) → 3H2(g) + 2Na3AlO3(aq). Hydrogen gas is explosive; mixing lye (sodium hydroxide) and aluminium in a closed container is therefore dangerous. In addition to aluminium, lye (sodium hydroxide) may also react with magnesium, zinc (galvanized), tin, chromium, brass, and bronze to produce hydrogen gas and is therefore dangerous. Do not allow lye to contact these metals.
Lye may react with various sugars to generate carbon monoxide, which is a poisonous gas; mixing sodium hydroxide and sugar in a closed container is therefore dangerous. Do not allow lye to contact sugar.


Personal protection for the safe handling of lye includes safety glasses, chemical-resistant gloves, and adequate ventilation. When in the close proximity of lye dissolving in an open container of water, a vapor-resistant face mask is recommended.


Lye is a deliquescent salt and has a strong affinity for moisture. Lye will deliquesce (dissolve or melt) when exposed to open air. It will absorb a relatively large amount of water from the atmosphere (air) if exposed to it. Eventually, it will absorb enough water to form a liquid solution because it will dissolve in the water it absorbs. Lye should be stored in an airtight resealable container.
Hygroscopic substances are often used as desiccants to draw moisture away from water-sensitive items. Desiccants should never be placed inside a canister of lye because lye has much stronger hygroscopic properties than activated carbon and silica gel (the most common ingredients in commercial desiccant packets) and will pull and absorb the water from the desiccant packets. Do not place desiccant packets inside containers of lye.
Lye should be stored in air-tight plastic containers. The containers should be labeled to indicate the potential danger of the contents and stored away from children, pets, heat, and moisture.

See also



lye in German: Alkalische Lösung
lye in Modern Greek (1453-): Αλισίβα
lye in Dutch: Alkalisch
lye in Polish: Ług
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