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

Silver oxide (CAS 20667-12-3): storage and disposal

In school, college and university stores, silver oxide is a fine brown-black powder, usually a small bottle bought for a single demonstration. It is classified as a strong oxidiser that may cause fire or explosion, as causing serious eye damage and as very toxic to aquatic life. The oxidiser statement is the strongest of the three and drives the rest of the advice.

CAS number
20667-12-3
Form
Solid
Storage class
Oxidiser
Signal word
Danger
Usual EWC code
16 05 06*
  • Oxidising pictogramOxidising
  • Corrosive pictogramCorrosive
  • 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

Anything organic is the main hazard to this bottle on a prep-room shelf. Paper labels, cardboard trays, wooden shelving, solvents and sugar-based stock should all be well away from it, because a strong oxidiser can make a fire far more intense. Keep ammonia based stock in a different cupboard altogether, since silver compounds that meet ammonia can become unstable as they dry. Acids and alkalis also belong elsewhere. Give it a labelled space on non-combustible shelving, in a tightly closed container shielded from strong light and heat, and write the date and quantity on the label. Check the shelf under the bottle for combustible lining paper and remove it.

How to tell it has deteriorated

A bottle of silver oxide should hold a dark, uniform powder. Because the oxide is sensitive to heat and light and can slowly give up oxygen, the signs to look for are a cap that has become tight or bulged, a bottle that has been stored on a sunny sill or beside a radiator, and powder with a dull, patchy or metallic grey surface where silver has been left behind. Staining of the shelf and corrosion of a metal cap point to a leak. Lumps, a damp look or any paper or organic dust inside the jar are worrying with a strong oxidiser, and the label should still be fully legible.

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.

A strong oxidiser is packed away from organics, solvents, acids and ammonia, so the grouping is the first thing a collector decides. Record the quantity, the colour and condition of the powder, and whether the cap is tight or the bottle looks bulged, and say plainly that it is silver oxide. A laboratory pack uses 16 05 06*, and discarded inorganic stock outside a laboratory pack uses 16 05 07*. It must never be tipped into a bin or a sink, and nobody should try to react it with another chemical to get rid of it. Keep the original bottle upright on a tray and request a specialist collection.

Waste codes and transport details for Silver oxide
EWC code, laboratory chemicals16 05 06*
Discarded inorganic chemical, not a laboratory pack16 05 07*
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.
  • 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.
  • Hydrochloric acidMany oxidisers release toxic gas or become unstable in contact with acid.
  • Mercury(II) chlorideToxic and oxidising stock are stored apart. A reaction could release toxic vapours.
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  • MethanolOxidisers can ignite flammable materials or make a fire far more intense.
  • Nitric acidMany oxidisers release toxic gas or become unstable in contact with acid.
  • Potassium hydroxideSome oxidisers react strongly with alkalis, and ammonia based stock is especially at risk.
  • Sodium cyanideToxic and oxidising stock are stored apart. A reaction could release toxic vapours.
  • Sodium hydroxideSome oxidisers react strongly with alkalis, and ammonia based stock is especially at risk.
  • Sulfuric acidMany oxidisers release toxic gas or become unstable in contact with acid.
  • Thionyl chlorideCorrosive stock can react with oxidisers, releasing heat or fumes.
  • TolueneOxidisers can ignite flammable materials or make a fire far more intense.
  • Zinc chlorideCorrosive stock can react with oxidisers, releasing heat or fumes.

Common quantities we collect

Usually held as: solid.

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

  • H271 May cause fire or explosion; strong oxidiser.
  • H318 Causes serious eye damage.
  • H410 Very toxic to aquatic life with long lasting effects.
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+P265 Wash hands and exposed skin thoroughly after handling. Do not touch eyes.
  • P273 Avoid release to the environment.
  • P280 Wear protective gloves, protective clothing, eye protection and face protection.
  • P283 Wear fire resistant or flame retardant clothing.
  • P305+P354+P338 IF IN EYES: Immediately rinse with water for several minutes. Remove contact lenses, if present and easy to do. Continue rinsing.
  • P306+P360 IF ON CLOTHING: Rinse immediately contaminated clothing and skin with plenty of water before removing clothes.
  • P317 Get medical help.
  • P370+P378 In case of fire: Use suitable extinguishing media to extinguish.
  • P371+P380+P375 In case of major fire and large quantities: Evacuate area. Fight fire remotely due to the risk of explosion.
  • P391 Collect spillage.
  • P420 Store separately.
  • P501 Dispose of contents and container in accordance with local, regional, national and international regulations.

Substance as classified, dilutions may differ.

Questions

Why is silver oxide treated differently from silver chloride?

It is classified as a strong oxidiser that may cause fire or explosion, as well as causing serious eye damage. Silver chloride carries only the aquatic hazard. The oxide needs separate oxidiser storage and grouping.

What should it be kept away from?

Organic material, solvents, acids, alkalis and ammonia based stock. Use non-combustible shelving, and remove any cardboard or paper lining that sits beneath the bottle, since a strong oxidiser makes any fire worse.

The bottle looks bulged. What should we do?

Do not open or squeeze it. Leave it where it is, away from heat and light, tell the person responsible for the store, and send an enquiry describing the swelling and the label.

Which waste code is used for an old bottle?

A laboratory pack uses 16 05 06*. A discarded bottle outside a laboratory pack uses 16 05 07*. Tell the collector which setting applies so that the paperwork matches.

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 Ag2O. EC number 243-957-1.

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