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Chemical collection and stock control for UK schools, universities and hospitals

Sodium metal: safe storage and disposal

Sodium metal (CAS 7440-23-5) is a soft silvery metal, kept under oil, and a familiar part of any school's Group 1 demonstrations. It reacts with water, releasing flammable hydrogen and enough heat to ignite it. Its GHS signal word is Danger. The hazard statements are H260 In contact with water releases flammable gases which may ignite spontaneously and H314 Causes severe skin burns and eye damage.

Fresh stock, properly kept, is manageable. The problem is old stock. Most sodium that reaches a disposal list has been sitting in a jar for many years, and that needs a different approach from a clean, recently bought lump.

If your sodium has lost its oil, has a crust or sits in a damaged or unlabelled jar, leave it where it is, keep water away from the area and get a specialist assessment. If there is immediate danger, evacuate and call 999.

CAS number
7440-23-5
Form
Solid
Storage class
Flammable
Signal word
Danger
Usual EWC code
16 05 06*
  • Flammable pictogramFlammable
  • Corrosive pictogramCorrosive

This chemical is a manual enquiry

This can become unstable or explosive, especially if it is old or has dried out. Nobody should move it until someone competent has looked at it, so we start with a conversation and usually a store assessment.

Reacts violently with water. Old pieces carry a crust of unknown composition.

It cannot be priced through a form. Please do not open or move it. Call us or send an enquiry and we will talk through the safe next step, which is often a store assessment.

What to do this week

  1. Leave it where it is. If it looks old, crystalline or damaged, do not open or move it and keep people away from the shelf.
  2. Write down the label wording, the rough age and where it is stored, from a safe distance.
  3. Send us those details, and a photo if you can take one without touching it.

Safe storage of sodium metal in a school or lab

Keep sodium in its original container, under the oil it was supplied with and with the lid closed. Keep the jar inside a sealed outer container, in a locked store, and keep it away from water, sinks, overhead pipes and any place where a leak or a sprinkler might reach it. Water-based stock should not be on the shelf above.

Hold a small amount. One or two small jars is ample for most schools, and many use far less. Sodium's place on your DSEAR assessment reflects the fire risk, and its place in your emergency plan matters because water cannot be used on it.

Check it at your stock check by looking through the side of the jar or outer container, without opening it. Record the oil level and the appearance of the metal, along with the date. Staff who use it should work to the risk assessment. Any scrap for disposal should stay under the assessed storage arrangements until a specialist collects it, and never go into a sink or a bin.

How to tell sodium metal has deteriorated

Sound sodium under clean oil looks like a dull grey or silver lump, and any fresh cut looks bright. With age it changes in ways you can see.

  • A white, yellow or grey crust on the surface, made of oxides and hydroxide
  • Oil that has dropped below the top of the metal, or has gone altogether
  • Oil that has darkened or thickened
  • A jar with a bulging or corroded lid, or a seized lid
  • A label so old it cannot be read
  • Lumps that have stuck together, or lie in a heap of white powder

A crust matters, as its composition is uncertain and it may react unpredictably when disturbed. Nobody should scrape it, cut it off or try to recover clean metal.

Forms a crust of mixed oxides and hydroxide as its oil cover is lost.

How sodium metal must be disposed of

Sodium metal is not accepted for routine collection. A specialist chemical store assessment is required before removal arrangements can be agreed. A specialist looks at the condition of the jar and the metal, decides how it can be packed and arranges its removal. The Department for Education's guidance advises that hazardous waste must go via a registered waste carrier and that schools should have arrangements in place to remove it.

Sodium is never poured, flushed, buried or put out with general or scrap metal waste. Do not try to destroy it yourself, however small the quantity, and do not follow older methods in textbooks. Even a small amount can react violently in a drain.

SettingUsual List of Wastes codeHazardous
Laboratory chemical, including school and university16 05 06*Yes
Discarded inorganic chemical, not in a laboratory pack16 05 07*Yes

For transport, sodium is UN 1428, packing group I. Expect the carrier to pack it individually under conditions that suit its condition. It will not simply join the other bottles in a lab pack.

Waste codes and transport details for Sodium metal
EWC code, laboratory chemicals16 05 06*
Hazardous wasteYes

The code depends on where the waste came from and what it is mixed with. Use the waste code finder to see why.

Do not store sodium metal with

  • Anything water-based, including acids, alkalis, ammonia solution and formalin. Water reacts with it, and leaks and fumes both count.
  • Chlorinated solvents, including chloroform, dichloromethane, carbon tetrachloride, 1,2-dichloroethane, 1,1,1-trichloroethane and tetrachloroethylene. These can react violently with reactive metals.
  • Hydrochloric acid, sodium hydroxide solution, hydrogen peroxide and sodium hypochlorite.
  • Bromine and carbon disulfide.
  • Oxidisers and corrosive stock as storage classes.

Its nearest relatives, potassium, lithium and calcium, need similar care, and old potassium is regarded as the more dangerous of the group. If you find them in the same old cupboard, list each with the same caution.

  • OxidiserOxidisers can ignite flammable materials or make a fire far more intense.
  • AcidOxidising acids can ignite flammable materials, and acid fumes attack containers and seals.
  • CorrosiveA leak of corrosive stock can break down flammable containers and feed a fire.

Named chemicals to keep apart

  • 1,1,1-TrichloroethaneAlkali metals can react explosively with chlorinated solvents.
  • 1,2-DichloroethaneAlkali metals can react explosively with chlorinated solvents.
  • Acetic acidOxidising acids can ignite flammable materials, and acid fumes attack containers and seals.
  • Ammonia solutionReacts with water, releasing heat and often a flammable or corrosive gas, so keep it away from all water based stock.
  • BromineBromine reacts violently with ammonia, reactive metals and many solvents.
  • Calcium hypochloriteOxidisers can ignite flammable materials or make a fire far more intense.
  • Carbon disulfideCarbon disulfide reacts violently with these materials.
  • Carbon tetrachlorideAlkali metals can react explosively with chlorinated solvents.
Show 15 more
  • ChloroformAlkali metals can react explosively with chlorinated solvents.
  • DichloromethaneAlkali metals can react explosively with chlorinated solvents.
  • FormalinReacts with water, releasing heat and often a flammable or corrosive gas, so keep it away from all water based stock.
  • Hydrochloric acidReacts with water, releasing heat and often a flammable or corrosive gas, so keep it away from all water based stock.
  • Hydrogen peroxideReacts with water, releasing heat and often a flammable or corrosive gas, so keep it away from all water based stock.
  • Nitric acidOxidising acids can ignite flammable materials, and acid fumes attack containers and seals.
  • Potassium nitrateOxidisers can ignite flammable materials or make a fire far more intense.
  • Potassium permanganateOxidisers can ignite flammable materials or make a fire far more intense.
  • Sodium hydroxideReacts with water, releasing heat and often a flammable or corrosive gas, so keep it away from all water based stock.
  • Sodium hypochloriteReacts with water, releasing heat and often a flammable or corrosive gas, so keep it away from all water based stock.
  • Sulfuric acidOxidising acids can ignite flammable materials, and acid fumes attack containers and seals.
  • TetrachloroethyleneAlkali metals can react explosively with chlorinated solvents.
  • Thionyl chlorideA leak of corrosive stock can break down flammable containers and feed a fire.
  • TrichloroethyleneAlkali metals can react explosively with chlorinated solvents.
  • Zinc chlorideA leak of corrosive stock can break down flammable containers and feed a fire.

Common quantities of sodium found

Schools usually have one small jar with a few lumps, sometimes older than the current staff. Colleges may hold a little more. In universities, sodium may also be found as wire, or in legacy solvent still residues, which are a separate and more dangerous problem. Any still residue should be left and assessed.

Usually held as: lumps under oil.

Part-used bottles and full containers are both fine. Tell us the size and how many, and an estimate is enough for a first price.

Sodium metal in different sectors

Schools and colleges. Sodium supports a demonstration that teachers value, so it often stays in stock for years. Make sure at least two people know where it is and how it should look. Ask your advisory service, CLEAPSS or SSERC, about current practice for the activity. If you no longer run the demonstration, plan for it to go while it is still in a sound condition.

Multi-academy trusts. Compare sites. It is common to find one school holding far more than it needs, or a jar that was forgotten during a merger or a building move.

Universities and research. Group turnover creates this problem, along with closed-down solvent stills. Your departmental safety officer should know about any reactive metal holdings, and a chemical handover should be part of every leaver's checklist.

Hazard data from PubChem GHS classification, retrieved 31 October 2026. Guidance only. Check your own risk assessment and your supplier's safety data sheet.

Hazard statements

  • H260 In contact with water releases flammable gases which may ignite spontaneously.
  • H314 Causes severe skin burns and eye damage.
Precautionary statements
  • P223 Do not allow contact with water.
  • P231+P232 Handle and store contents under inert gas. Protect from moisture.
  • P260 Do not breathe dust, fume, gas, mist, vapours or spray.
  • P264 Wash hands and exposed skin thoroughly after handling.
  • P280 Wear protective gloves, protective clothing, eye protection and face protection.
  • P301+P330+P331 IF SWALLOWED: Rinse mouth. Do NOT induce vomiting.
  • P302+P335+P334 IF ON SKIN: Brush off loose particles from skin. Immerse in cool water or wrap in wet bandages.
  • 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.
  • P321 Specific treatment (see supplemental first aid instruction on this label).
  • P363 Wash contaminated clothing before reuse.
  • P370+P378 In case of fire: Use suitable extinguishing media to extinguish.
  • P402+P404 Store in a dry place. Store in a closed container.
  • P405 Store locked up.
  • P501 Dispose of contents and container in accordance with local, regional, national and international regulations.

Substance as classified, dilutions may differ.

Questions

Can we use up old sodium in a class demonstration to clear it?

No. Old pieces carry a crust of unknown composition and must not be cut, scraped or used up. The reaction with water is violent even for sound metal, and a crusted piece is less predictable. Leave the jar where it is, keep it dry and send an enquiry.

The oil in our sodium jar has gone low. Should we top it up?

No. A low level is a warning sign, because the metal may already have met air and started to form a crust. Do not open the jar or add anything to it. Keep the area dry and describe what you can see from outside in your enquiry.

Who actually needs to look at a crusted jar of sodium?

A competent chemist assesses it in person, and where warning signs are present it may need an explosives or emergency specialist. A general collection crew cannot decide this from a description. Your enquiry starts that process, so include a clear account of the jar and its surroundings.

Our sodium jar is in the solvent cabinet next to chloroform. What should we do?

Report that placement in your enquiry, because alkali metals can react explosively with chlorinated solvents. Do not open the jar, and leave it undisturbed until advice is received. List the other bottles sharing the cabinet as well, since the person assessing it will want to know them.

Guidance only. Check your own risk assessment and your supplier's safety data sheet.

Hazard data source: PubChem GHS Classification, retrieved 31 Oct 2026. Formula Na. EC number 231-132-9.

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