Safety data reference
Caustic Soda (Sodium Hydroxide) — Safety Data Summary
- CAS1310-73-2
- EC215-185-5
- FormulaNaOH
- MW40.00 g/mol
Read this before you use this page
This is a general reference summary for Caustic Soda (Sodium Hydroxide), compiled from publicly published authoritative sources — PubChem, the NIOSH Pocket Guide, ILO/WHO International Chemical Safety Cards, CAMEO Chemicals, the ECHA C&L Inventory, OSHA and the eCFR. Every figure on this page is traceable to one of the sources listed at the foot of the page.
It is not a supplier safety data sheet and must not be used as one. A compliant SDS is batch-specific and manufacturer-specific: it carries the actual supplier identity, emergency contact, product identifier, grade, impurity profile and the classification that follows from them. Before you accept, store, handle or ship any consignment, obtain the manufacturer’s own signed SDS for that grade and lot.
01Hazard identification
Classification: Skin corrosion, Category 1A (EU harmonised) · Serious eye damage, Category 1 · Corrosive to metals, Category 1 (self-classified)
Pictograms: GHS05 Corrosion
- H314 Causes severe skin burns and eye damage.
- H318 Causes serious eye damage.
- H290 May be corrosive to metals.
Identification
| IUPAC name | sodium hydroxide |
|---|---|
| Synonyms | Caustic soda, lye, soda lye, sodium hydrate, white caustic |
| CAS number | 1310-73-2 |
| EC number | 215-185-5 |
| Molecular formula | NaOH |
| Molecular weight | 40.00 g/mol |
02Precautionary statements
Prevention
- P234 Keep only in the original container.
- P260 Do not breathe dust, fume, gas, mist, vapours or spray.
- P264 Wash hands thoroughly after handling.
- P280 Wear protective gloves, protective clothing, eye protection and face protection.
Response
- P301+P330+P331 IF SWALLOWED: Rinse mouth. Do NOT induce vomiting.
- P302+P361+P354 IF ON SKIN: Take off immediately all contaminated clothing. Immediately rinse with water for several minutes.
- P304+P340 IF INHALED: Remove person to fresh air and keep comfortable for breathing.
- P305+P354+P338 IF IN EYES: Immediately rinse with water for several minutes. Remove contact lenses if present and easy to do. Continue rinsing.
- P316 Get emergency medical help immediately.
- P363 Wash contaminated clothing before reuse.
- P390 Absorb spillage to prevent material damage.
Storage
- P405 Store locked up.
- P406 Store in a corrosion-resistant container with a resistant inner liner.
Disposal
- P501 Dispose of contents and container in accordance with local, regional and national regulations.
03Physical and chemical properties
| Appearance | Colourless to white, deliquescent solid — flakes, beads or granules |
|---|---|
| Odour | Odourless |
| pH | 0.05% solution approx. 12; 0.5% approx. 13; 5% approx. 14 |
| Melting point | 323 °C |
| Boiling point | 1388 °C |
| Flash point | Not applicable — non-combustible solid |
| Flammability | Non-combustible. NFPA 704: Health 3, Flammability 0, Instability 1 |
| Explosive limits | Not applicable |
| Vapour pressure | Approximately 0 mmHg |
| Relative density | 2.13 at 25 °C |
| Water solubility | 109 g/100 mL at 20 °C (111%) |
| log Kow | Not applicable — inorganic ionic solid |
| Viscosity | 4.0 mPa·s at 350 °C (molten) |
| Decomposition temp. | No discrete value; emits sodium oxide fumes on decomposition |
| Hygroscopicity | Deliquescent; absorbs CO2 and water from air, converting to sodium carbonate |
04Exposure controls and occupational limits
| OSHA PEL | 2 mg/m3, 8-hour TWA |
|---|---|
| NIOSH REL | Ceiling 2 mg/m3, 15 minutes |
| ACGIH TLV | Ceiling 2 mg/m3 |
| NIOSH IDLH | 10 mg/m3 |
| Respirator selection | Up to 10 mg/m3: APF 25 supplied-air continuous flow, or APF 50 full-facepiece air-purifying with N100/R100/P100. IDLH or unknown: APF 10,000 pressure-demand SCBA |
05First-aid measures
- Inhalation
- Fresh air, rest. Refer immediately for medical attention. If breathing has stopped, perform artificial respiration; keep warm and at rest. Do NOT perform mouth-to-mouth resuscitation.
- Skin contact
- Remove contaminated clothing. Rinse skin with plenty of water or shower for at least 15 minutes — the ERG recommends at least 30 minutes for corrosives. Refer immediately for medical attention.
- Eye contact
- Irrigate immediately. Flush with large amounts of water for at least 15 minutes, occasionally lifting the lower and upper lids. Remove contact lenses if easily possible. Get medical attention immediately.
- Ingestion
- Rinse mouth. Do NOT induce vomiting. If within a few minutes of ingestion, one small glass of water may be given. Refer immediately for medical attention.
06Fire-fighting measures
- Suitable extinguishing media
- Use the agent suitable for the surrounding fire. Small fire: dry chemical, CO2, water spray. Large fire: dry chemical, CO2, alcohol-resistant foam, water spray.
- Unsuitable media
- Do not get water inside containers. Avoid a direct water jet onto solid caustic — dissolution is violently exothermic and causes spattering.
- Specific hazards
- Non-combustible, but decomposes on heating to corrosive and toxic fumes. Contact with aluminium, zinc and tin evolves flammable hydrogen. Containers may explode when heated. Runoff may be corrosive and cause pollution. The heat of dissolution can ignite adjacent combustible material.
- Protective equipment
- Positive-pressure SCBA plus chemical protective clothing. Structural firefighting clothing gives limited protection in fire only, not in spill situations. Use water spray to keep fire-exposed containers cool and keep runoff out of sewers and water sources.
- ERG guide
- Guide 154 (Substances — toxic and/or corrosive, non-combustible)
07Accidental release measures
- Personal precautions
- Keep unauthorised personnel away. Stay upwind, uphill and upstream. Ventilate closed spaces before entry. Wear a chemical protection suit including self-contained breathing apparatus. Do not touch damaged containers or spilled material without appropriate protective clothing.
- Environmental precautions
- Do not let the chemical enter the environment. Prevent entry into waterways, sewers, basements or confined areas.
- Containment and clean-up
- Sweep spilled substance into covered plastic or steel containers and carefully collect the remainder. For land spills, construct barriers or dike and shovel promptly into steel containers. Absorb liquid with sand, vermiculite or other inert absorbent. For water spills, use booms to limit travel and neutralise with dilute acid. Do NOT get water inside containers.
- ERG isolation distances
- Isolate the spill or leak area in all directions for at least 25 m (75 ft) for solids, 50 m (150 ft) for liquids. Fire involving a tank: isolate and consider evacuation for 800 m (half a mile) in all directions.
08Handling and storage
- Safe handling
- Avoid breathing dust or mist and avoid all bodily contact. Keep upwind. Provide adequate ventilation where caustic dust or mist is present. Wear safety goggles with side shields plus a face shield, rubber gloves, boots and apron, and safety shoes. Eyewash fountains and quick-drench safety showers are required at any location where eye or skin contact can occur. When diluting from concentrations above 25%, always add caustic to water, never the reverse.
- Safe storage
- Store in a cool, dry, well-ventilated location. Keep containers tightly closed, which also prevents conversion to sodium carbonate by atmospheric CO2. Store only in the original container, separated from food and feedstuffs, strong acids and metals. Use an area without drain or sewer access. Nickel is the preferred material of construction at all concentrations and temperatures; mild steel is adequate for most applications.
- Incompatible materials
- Water (uncontrolled addition); all mineral and organic acids; flammable liquids; organic halogens; aluminium, tin, zinc and lead; nitromethane; ammonium salts; oxidising materials; metal powders; nitro compounds. Attacks glass.
09Stability and reactivity
- Reactivity
- Strong base. Reacts rapidly and exothermically with acids. Water-reactive through its heat of dissolution. Slowly absorbs CO2 from air, forming crusts of sodium carbonate.
- Chemical stability
- Stable under normal conditions. Hygroscopic and deliquescent. Does not polymerise.
- Hazardous reactions
- Dissolution or dilution liberates enough heat to cause steaming, spattering and local boiling. With solutions at 40% and above, the heat can raise the temperature past boiling point and cause dangerous eruptions. Attacks aluminium, zinc, tin and lead with liberation of flammable hydrogen gas. Reacts with ammonium salts to release ammonia. Catalyses dangerous polymerisations.
- Conditions to avoid
- Uncontrolled contact with moisture or water, heat, CO2 exposure, and contact with incompatible materials.
- Decomposition products
- Sodium oxide fumes on thermal decomposition; hydrogen gas on contact with reactive metals.
10Toxicological information
| LD50 oral, rat | 140–340 mg/kg |
|---|---|
| LD50 dermal, rabbit | 1,350 mg/kg |
| LC50 inhalation, rat | No data available — non-volatile solid |
| Routes of exposure | Inhalation, ingestion, skin contact and eye contact. Serious local effects by all routes |
| Symptoms | Irritation of the eyes, skin and mucous membrane; pneumonitis; eye and skin burns. Inhalation: cough, sore throat, burning sensation, shortness of breath. Skin: redness, pain, serious burns, blisters. Eye: redness, pain, blurred vision, severe burns. Ingestion: abdominal pain, burns in the mouth and throat, nausea, vomiting, shock or collapse |
| Target organs | Eyes, skin, respiratory system |
| IARC | Not evaluated / not classified |
| NTP | Not listed in the Report on Carcinogens |
| OSHA | Not regulated as a carcinogen |
11Ecological information
| LC50 fish | Goldfish (Carassius auratus) 24 h 160 mg/L; guppy (Poecilia reticulata) 24 h 209 mg/L |
|---|---|
| EC50 invertebrate | Ceriodaphnia dubia 48 h EC50 40.38 mg/L, immobilisation |
| Chronic effects | Guppies chronically exposed to 25 mg/L and above showed decreased survival, reduced weight gain and impaired fertility |
| Biodegradability | Not applicable — inorganic. No BOD |
| Bioaccumulation | Not expected — inorganic ionic substance |
| Mobility in soil | Dissolves readily; solid spills on soil dissolve on precipitation and the resulting solution can infiltrate and pollute groundwater. The effect is governed by pH and is neutralised by soil buffering |
12Transport information
| UN number | UN 1823 (solid). UN 1824 for solution |
|---|---|
| Proper shipping name | Sodium hydroxide, solid |
| Transport hazard class | 8 — Corrosive |
| Packing group | II |
| Marine pollutant | No — not listed in 49 CFR 172.101 Appendix B |
| ERG guide | 154 |
| Air freight limits | Passenger aircraft and rail 15 kg; cargo aircraft only 50 kg |
| Additional | Do not transport with food and feedstuffs |
13Regulatory information
| TSCA | Listed on the TSCA Inventory; subject to Chemical Data Reporting |
|---|---|
| SARA 313 (TRI) | Not listed in 40 CFR 372.65 |
| California Prop 65 | Not listed |
| EU REACH | Registered; CLP Annex VI harmonised entry Index 011-002-00-6 |
| CERCLA RQ | 1,000 lb (454 kg) — 40 CFR 302.4 |
| Clean Water Act | Designated a hazardous substance under CWA §311(b)(2)(A) |
| RCRA | No listed waste code. Waste may be characteristically hazardous as D002 (corrosivity) |
| FDA | GRAS direct food additive as a pH control agent |
Frequently asked questions
Why does caustic soda get hot when mixed with water?
Dissolving sodium hydroxide releases a large heat of solution. With concentrated preparations the temperature can pass the boiling point of water, causing steam flashing and violent spattering of a corrosive liquid. This is why caustic is always added to water in small increments with agitation and cooling, and never the reverse.
What packing group is caustic soda flakes?
Solid sodium hydroxide ships as UN 1823, Class 8 corrosive, packing group II, with ERG guide 154. Solutions ship as UN 1824 and may fall in packing group II or III depending on measured corrosivity. It is not a marine pollutant.
What gloves protect against sodium hydroxide?
Natural rubber, neoprene, nitrile and SBR-coated fabric all give more than one hour of breakthrough resistance to caustic. The greater risk in practice is eye exposure, so goggles plus a face shield are required wherever splashing is possible, along with an accessible eyewash and safety shower.
Does caustic soda react with aluminium?
Yes, and dangerously so. Sodium hydroxide attacks aluminium, zinc, tin and lead, liberating flammable hydrogen gas. Never store or transfer caustic in aluminium vessels. Nickel is the preferred material of construction at all concentrations and temperatures, with mild steel adequate for most ambient-temperature applications.
What is the exposure limit for sodium hydroxide?
The OSHA PEL is 2 mg/m³ as an 8-hour TWA, while NIOSH and ACGIH both set 2 mg/m³ as a ceiling value that must not be exceeded at any time. The IDLH is 10 mg/m³. Because the hazard is corrosive rather than systemic, a ceiling limit is the more meaningful control.
Supply
We supply Caustic Soda Flakes 99% (Sodium Hydroxide) in bulk from Chinese manufacturing plants, with a batch certificate of analysis and the manufacturer’s signed safety data sheet shipped against every consignment. Tell us the grade, volume and destination port and we will come back with packing options, lead time and a delivered price.
Sources
Every value on this page was taken from one of the following public authorities. Where an authority records no verified value, this page says so rather than substituting an estimate.
- PubChem — National Library of Medicine
- NIOSH Pocket Guide to Chemical Hazards
- ILO/WHO International Chemical Safety Cards
- CAMEO Chemicals — NOAA
- ECHA Classification & Labelling Inventory
- OSHA Annotated Permissible Exposure Limits
- eCFR Title 49 §172.101 Hazardous Materials Table
Compiled September 2026. Regulatory lists and classifications change; verify against the current source text before relying on this page for a compliance decision.