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

Sodium nitrite (CAS 7632-00-0): storage and disposal

Pathology and histology benches hold sodium nitrite as the solid and as a 1% solution, and school, college and university stores keep the solid. It is an oxidiser, toxic if swallowed and very toxic to aquatic life, with eye irritation. Its reactions with acids and with ammonium salts are what turn a quiet white powder into a storage problem.

CAS number
7632-00-0
Form
Solid
Storage class
Oxidiser
Signal word
Danger
Usual EWC code
16 05 06*
  • Oxidising pictogramOxidising
  • Acute toxicity pictogramAcute toxicity
  • Hazardous to the environment pictogramHazardous to the environment

What to do this week

  1. Check the label is readable and write down the opened date if it is not already there.
  2. Check it is stored as oxidiser stock and apart from the items listed under "Do not store with".
  3. If you no longer need it, add it to your disposal list so it goes on the next collection.

Safe storage in a school or lab

Acids and ammonium salts are the two things this solid must not sit beside. Nitrites release toxic nitrogen oxides with acids such as hydrobromic acid, and nitrites and ammonium salts, including ammonium nitrate, ammonium sulfate, ammonium carbonate and ammonium chloride, can react violently on heating. Sodium nitrite sits in a separate, labelled, non-combustible space away from flammable, organic and reducing materials, and in a locked cabinet because of the oral toxicity. It also reacts with amines to form suspected carcinogens, so keep amine stock elsewhere. Histology labs holding 1% solution should label it clearly and keep it in a tray.

How to tell it has deteriorated

Few distinctive visual signs mark this salt, so look at the container. Caking, a damp appearance, staining of the shelf, corroded caps and contamination with paper or organic dust are the oxidiser checks that apply. Brown fumes near the jar suggest acid contact and mean the jar should be left closed. A solution bottle may show a faded label, crust under the cap or a low level. Because the contents are toxic if swallowed, nobody should open an old jar to inspect it, and a jar with no label is treated as unknown stock.

How it must be disposed of

By specialist collection only. It never goes down the drain or into general waste. It is normally packed in a oxidising laboratory pack with compatible chemicals.

The waste code for laboratory chemicals applies, the inorganic discarded-chemical variant covers it outside a lab pack, and a hospital holder uses the healthcare code. Say whether it is solid or 1% solution, give the quantity and record the cap condition. Sodium nitrite is very toxic to aquatic life, so it never goes down a sink or drain, and it must not be added to acids or amines to get rid of it. The specialist carrier packs it as an oxidiser, apart from acids, ammonium salts and organic stock.

Waste codes and transport details for Sodium nitrite
EWC code, laboratory chemicals16 05 06*
Discarded inorganic chemical, not a laboratory pack16 05 07*
Human healthcare setting18 01 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 with

  • FlammableOxidisers can ignite flammable materials or make a fire far more intense.
  • AcidMany oxidisers release toxic gas or become unstable in contact with acid.
  • AlkaliSome oxidisers react strongly with alkalis, and ammonia based stock is especially at risk.
  • ToxicToxic and oxidising stock are stored apart. A reaction could release toxic vapours.
  • CorrosiveCorrosive stock can react with oxidisers, releasing heat or fumes.

Named chemicals to keep apart

  • Acetic acidMany oxidisers release toxic gas or become unstable in contact with acid.
  • AcetoneOxidisers can ignite flammable materials or make a fire far more intense.
  • Ammonia solutionSome oxidisers react strongly with alkalis, and ammonia based stock is especially at risk.
  • Ammonium acetateNitrites and ammonium salts can react violently on heating.
  • Ammonium carbonateNitrites and ammonium salts can react violently on heating.
  • Ammonium chlorideNitrites and ammonium salts can react violently on heating.
  • Ammonium nitrateNitrites and ammonium salts can react violently on heating.
  • Ammonium oxalateNitrites and ammonium salts can react violently on heating.
Show 16 more
  • Ammonium sulfateNitrites and ammonium salts can react violently on heating.
  • Ammonium thiocyanateNitrites and ammonium salts can react violently on heating.
  • EthanolOxidisers can ignite flammable materials or make a fire far more intense.
  • FormalinToxic and oxidising stock are stored apart. A reaction could release toxic vapours.
  • HexaneOxidisers can ignite flammable materials or make a fire far more intense.
  • Hydrobromic acidNitrites release toxic nitrogen oxides with acids.
  • Hydrochloric acidNitrites release toxic nitrogen oxides with acids.
  • Hydroiodic acidNitrites release toxic nitrogen oxides with acids.
  • Mercury(II) chlorideToxic and oxidising stock are stored apart. A reaction could release toxic vapours.
  • MethanolOxidisers can ignite flammable materials or make a fire far more intense.
  • Nitric acidNitrites release toxic nitrogen oxides with acids.
  • Perchloric acidNitrites release toxic nitrogen oxides with acids.
  • Phosphoric acidNitrites release toxic nitrogen oxides with acids.
  • Potassium hydroxideSome oxidisers react strongly with alkalis, and ammonia based stock is especially at risk.
  • Sulfuric acidNitrites release toxic nitrogen oxides with acids.
  • Trichloroacetic acidNitrites release toxic nitrogen oxides with acids.

Common quantities we collect

Usually held as: solid, 1% solution.

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.

Where it is commonly held

Hazard statements

  • H272 May intensify fire; oxidiser.
  • H301 Toxic if swallowed.
  • H319 Causes serious eye irritation.
  • H400 Very toxic to aquatic life.
Precautionary statements
  • P210 Keep away from heat, hot surfaces, sparks, open flames and other ignition sources. No smoking.
  • P220 Keep away from clothing and other combustible materials.
  • P264 Wash hands and exposed skin thoroughly after handling.
  • P270 Do not eat, drink or smoke when using this product.
  • P273 Avoid release to the environment.
  • P280 Wear protective gloves, protective clothing, eye protection and face protection.
  • P301+P316 IF SWALLOWED: Get emergency medical help immediately.
  • P321 Specific treatment (see supplemental first aid instruction on this label).
  • P330 Rinse mouth.
  • P370+P378 In case of fire: Use suitable extinguishing media to extinguish.
  • P391 Collect spillage.
  • P405 Store locked up.
  • P501 Dispose of contents and container in accordance with local, regional, national and international regulations.
  • P264+P265 Wash hands and exposed skin thoroughly after handling. Do not touch eyes.
  • P305+P351+P338 IF IN EYES: Rinse cautiously with water for several minutes. Remove contact lenses, if present and easy to do. Continue rinsing.
  • P337+P317 If eye irritation persists: Get medical help.

Substance as classified, dilutions may differ.

Questions

Why must sodium nitrite be kept away from ammonium salts?

Nitrites and ammonium salts can react violently on heating. Keep them in separate cabinets, never share a shelf or tray, and note this in the stores plan.

What happens when it meets an acid?

Nitrogen oxides are released, which is why acids are always stored away from it. Do not combine leftover nitrite with acid for any reason, including to use it up.

Does the 1% solution need locking up?

The solution may be less hazardous than the solid, but the label and storage should follow the supplier safety data sheet. Keep it labelled, separated from acids and ammonium salts, and collected with the solid.

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 NNaO2. EC number 231-555-9.

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