Sodium hydroxide

CAS1310-73-2

Molecular formulaHNaO

Molar mass39.997 g/mol

Hazardous

Hazards Summary | At room temperature, sodium hydroxide is a white crystalline odorless solid that absorbs moisture from the air. It is a manufactured substance. When dissolved in water or neutralized with acid it liberates substantial heat, which may be sufficient to ignite combustible materials. Sodium hydroxide is very corrosive. It is generally used as a solid or a 50% solution. Other common names include caustic soda and lye. Sodium hydroxide is used to manufacture soaps, rayon, paper, explosives, dyestuffs, and petroleum products. It is also used in processing cotton fabric, laundering and bleaching, metal cleaning and processing, oxide coating, electroplating, and electrolytic extracting. It is commonly present in commercial drain and oven cleaners.

Scientific Grain Officer - Dictionary Editorial Department, revised at:2026-10-19

Toxicity

Fate Summary

AQUATIC FATE: In the case of a solid, anhydrous sodium hydroxide spill on soil, ground water pollution will occur if precipitation occurs prior to clean up. Precipitation will dissolve some of the solid (with much heat given off) and create an aqueous solution of sodium hydroxide, which then would be able to infiltrate the soil. However, prediction of the concentration and properties of the solution produced would be difficult.

Environmental Biodegradation

BOD: none

Environmental Water Concentrations

GROUNDWATER: Sodium hydroxide was identified as a chemical of concern in wells associated with the Pavilion Area Groundwater Plume in Pavilion Wyoming in Fremont County. Land use in the area is agricultural with some properties used for natural gas production. Sampling was conducted from March 2 through 6, 2009 and May 14, and 15, 2009(1).

Ecotoxicity Excerpts

/AQUATIC SPECIES/ Chronic exposure of guppies to sodium hydroxide (> or =25 mg/L) decreased their survival rate and weight gain, and caused either late or premature sexual maturity resulting in decreased fertility.

Effluent Concentrations

Estimated emissions of sodium hydroxide as one of the typical pollutants released from the synthetic organic chemical manufacturing industry (production/processing) may range from (unit process, product): alkylation, ethylbenzene, 1.9 to 21.5; condensation, polyethylene terephthalate, 0.065 to 23.1; dehydrogenation, isoprene, 0.5 to 19; dehydrohalogenation, vinylidene chloride, 45.5 to 605.5; polymerization, polyethylene terephthalate, 0.1 to 23.1 (all in g/kg produced)(1). The compound was spilled at an estimated 3,500 gallons into the Newark Bay on October 1991 from the Gist Brocades facility(2). Sodium hydroxide was involved in 2.6% of 6,928 chemical accidents in the US over a 5 year period up to 1985 at a reportable quantity of 2200 kg(3).

ICSC Environmental Data

This substance may be hazardous to the environment. Special attention should be given to aquatic organisms.

Probable Routes of Human Exposure

Inhalation of dust or mist, ingestion, and skin or eye contact.

Symptoms

irritation eyes, skin, mucous membrane; pneumonitis; eye, skin burns; temporary loss of hair

Target Organs

Eyes, skin, respiratory system

Adverse Effects

Toxic Pneumonitis - Inflammation of the lungs induced by inhalation of metal fumes or toxic gases and vapors.

Exposure Routes

inhalation, ingestion, skin and/or eye contact

Toxicity Summary

Cosmetic Ingredient Review Finding(s): Safe for use in cosmetics, with qualifications

RAIS Toxicity Values

Inhalation Acute Reference Concentration Reference: CALEPA

Non-Human Toxicity Values

LD50 Mouse ip 40 mg/kg