Sodium hydroxide

E number E524INS 524CAS 1310-73-2

Used as an acidity regulator.

Sodium hydroxide, or lye, is a strongly alkaline processing aid. It gives pretzels their crust and colour, cures olives, and produces hominy from maize; it is normally neutralised or washed out.

Where it is and isn’t permitted

Status of Sodium hydroxide by jurisdiction. Every jurisdiction this site covers is listed, including those where the substance does not appear.
JurisdictionStatusScope and limitsCitation
United StatesFood and Drug AdministrationPermitted21 CFR 184.1763retrieved 2026-09-07
Codex AlimentariusCodex Alimentarius Commission / JECFAPermitted, with conditions

8 food categories

highest permitted level 2,000 mg/kg

Show every food category
  • 01.1.2 Other Fluid Milk (plain) — GMP
  • 01.2.1.2 Fermented milks (plain), heat-treated after fermentation — GMP
  • 01.8.2 Dried whey and whey products, excluding whey cheeses — GMP
  • 02.2.1 Butter — GMP
  • 13.1.1 Infant formulae — 2,000 mg/kg
  • 13.1.2 Follow-up formulae — GMP
  • 13.1.3 Formulae for special medical purposes for infants — 2,000 mg/kg
  • 13.2 Complementary foods for infants and young children — GMP
CXS 192-1995 Table Three, INS 524and 8 further provisionsretrieved 2026-09-07

What it is made from

Manufactured by the electrolysis of brine. It is corrosive as supplied and is handled as a processing aid rather than an ingredient.

  • Vegan
  • Vegetarian
CAS registry number
1310-73-2
InChIKey
HEMHJVSKTPXQMS-UHFFFAOYSA-M
PubChem
CID 14798

Every name it appears under

65 recorded names. A label may use any of them.

E number

  • E524

INS number

  • 524

CAS registry number

  • 1310-73-2
  • 81133-20-2

As it appears in regulation

  • Sodium hydroxide

Other names

  • Aetznatron
  • Ascarite
  • Ascarite II
  • Caswell No. 773
  • Caustic soda
  • Caustic soda, bead
  • Caustic soda, dry
  • Caustic soda, liquid
  • Collo-Grillrein
  • Collo-Tapetta
  • E 524
  • EPA Pesticide Chemical Code 075603
  • Fuers Rohr
  • HSDB 229
  • Hydroxide, Sodium
  • Hydroxyde de sodium
  • hydroxyl sodium
  • INS-524
  • Lewis-red devil lye
  • Liquid-plumr
  • Lye
  • NaOH
  • Natrii hydroxydum
  • Natrium causticum
  • Natrium-hydroxid, reinstes
  • Natriumhydroxid
  • Natriumhydroxyde
  • Plung
  • Promoter 3308b
  • Rohrputz
  • Rohrreiniger Rofix
  • Soda asbestos
  • Soda lye
  • Soda, caustic
  • Soda, hydrate
  • Soda, kaustische
  • Sodio(idrossido di)
  • sodium hydoxide
  • Sodium hydrate
  • sodium hydroxid
  • Sodium hydroxide
  • Sodium Hydroxide (0.1M in water (0.1N))
  • Sodium hydroxide (Na(OH))
  • Sodium hydroxide (Na2(OH)2)
  • Sodium hydroxide dimer
  • Sodium hydroxide pearls
  • Sodium hydroxide, flake
  • Sodium hydroxide, pellets
  • Sodium hydroxide, solid
  • Sodium hydroxide; NaOH
  • sodium hyroxide
  • Sodium(hydroxyde de)
  • sodiumhydroxid
  • sodiumhydroxide
  • soude caustique
  • Stamperprep
  • Tosoh pearl
  • UN 1823 (solid)
  • White caustic

Systematic names

  • Sodium;hydroxide

Hazard reference values

No reference value for this substance in the sources we hold.

Evidence and how bodies read it

Studies, and the differing conclusions regulators drew from them, are curated by hand rather than machine-read, and none has been written for this substance yet.

Sources for this page

  • ecfr retrieved 2026-09-07
  • gsfa retrieved 2026-09-07

Full licence terms and publisher details on Sources. How this page is built and updated: Method.

Machine-readable:/api/v1/additives/sodium-hydroxide.json