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

Silver nitrate (CAS 7761-88-8): storage and disposal

Silver nitrate is held in school prep rooms as a solid and as 0.1 M solution, in histology labs for silver staining, and in clinics, veterinary practices and dental surgeries as caustic pencils. It is classified as an oxidiser that may intensify fire, as causing severe skin burns and eye damage, and as very toxic to aquatic life. It also blackens skin.

CAS number
7761-88-8
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

Dark glass is there for a reason, since the salt darkens where light reaches it, so never move it into clear bottles or leave a bottle on a bench. Ammonia solution is the neighbour to avoid above all, because with ammonia it can deposit explosive silver compounds. Keep ethanol, acetylene cylinders and magnesium ribbon clear for the same reason, and keep it away from organic material generally. As an oxidiser it needs its own labelled space on non-combustible shelving, apart from solvents, acids, alkalis and corrosive stock. Clinic and surgery caustic pencils should stay in their sealed tube in a locked drawer, separate from dressings and alcohol wipes.

How to tell it has deteriorated

Darkening is the sign to look for. Silver nitrate goes grey, then brown or black where light or organic dust has reached it, so a white crystalline solid that has turned patchy and dull has been exposed. A 0.1 M bottle may show a dark deposit or a stained neck. Caustic pencils darken and may crumble in a tube that is not sealed, and the stain spreads to the packaging. Black marks on shelves, labels and gloves point to leaks. A dark film inside the stopper or a bottle that has been refilled from another container should be recorded before anything else is done.

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 code depends on who holds it. A laboratory pack uses 16 05 06*, discarded inorganic stock outside a pack uses 16 05 07*, a human healthcare setting such as a clinic or dental surgery uses 18 01 06*, and a veterinary practice uses 18 02 05*. Describe the solid, the 0.1 M solution and any caustic pencils as separate items. Silver residues must never go into a drain or the clinical waste, and ammonia must never be used to clean a stained bottle. UN 1493 is the carriage entry. The carrier packs it apart from ammonia, organics and solvents, so keep the original dark container and request a specialist collection.

Waste codes and transport details for Silver nitrate
EWC code, laboratory chemicals16 05 06*
Discarded inorganic chemical, not a laboratory pack16 05 07*
Human healthcare setting18 01 06*
Veterinary setting18 02 05*
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.
  • AcetyleneSilver nitrate can form explosive silver compounds with these materials.
  • Ammonia solutionSilver nitrate can form explosive silver compounds with these materials.
  • EthanolSilver nitrate can form explosive silver compounds with these materials.
  • 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.
Show 11 more
  • Magnesium ribbonSilver nitrate can form explosive silver compounds with these materials.
  • 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 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, 0.1 M, caustic pencils.

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.
  • H314 Causes severe skin burns and 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.
  • P260 Do not breathe dust, fume, gas, mist, vapours or spray.
  • P264 Wash hands and exposed skin thoroughly after handling.
  • P273 Avoid release to the environment.
  • P280 Wear protective gloves, protective clothing, eye protection and face protection.
  • 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.
  • 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.
  • P391 Collect spillage.
  • 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

Why must silver nitrate be kept away from ammonia?

With ammonia it can deposit explosive silver compounds. Keep ammonia solution, ethanol, acetylene and magnesium ribbon well away, and never use ammonia to clean a stained silver nitrate bottle.

Our caustic pencils have turned black. Are they still usable?

Darkening means light or organic matter has reached them. They are classified as causing severe burns, so treat them as stock to dispose of. Keep them sealed and include them in the collection request.

Which waste code should a veterinary practice use?

A veterinary setting uses 18 02 05*. A human healthcare setting uses 18 01 06*, and a laboratory pack uses 16 05 06*. Say which one applies when you request collection.

Can stained gloves and wipes go in the clinical bin?

No. Contaminated items carry silver residue and count as hazardous waste, because the salt is very toxic to aquatic life. Bag them separately from other clinical waste, label the bag clearly, and mention them when you send your enquiry.

Why is it kept in dark glass?

The salt darkens in light. Dark glass slows that change. Do not decant it into a clear container, and keep the bottle shut and out of direct light.

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 AgNO3. EC number 231-853-9.

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