Skip to content

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

Ammonium dichromate (CAS 7789-09-5): storage and disposal

Most ammonium dichromate in school, college and university stores is legacy stock from the old volcano demonstration. It is a chromium(VI) compound that may cause cancer and genetic defects, is fatal if inhaled and may intensify a fire. It also decomposes vigorously on heating, and the condition of old jars is unknown. Each holding therefore goes through a manual enquiry and not an online quote, and it is never to be used up in one last demonstration.

CAS number
7789-09-5
Form
Solid
Storage class
Oxidiser
Signal word
Danger
Usual EWC code
16 05 06*
  • Oxidising pictogramOxidising
  • Corrosive pictogramCorrosive
  • Acute toxicity pictogramAcute toxicity
  • Serious health hazard pictogramSerious health hazard
  • Hazardous to the environment pictogramHazardous to the environment

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.

Decomposes vigorously on heating, sensitive legacy stock.

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 in a school or lab

Heat decides where it goes. Vigorous decomposition rules out a radiator shelf, a sunny window and the top of a cupboard over a hot pipe, all of which are familiar places for a forgotten jar. It belongs in the separate oxidiser space, on non-combustible shelving where possible, with flammable stock elsewhere. As an ammonium salt it also needs to be kept away from alkalis, and from acids, as many oxidisers become unstable with them. Old demonstration boxes are a further worry, because a jar may be stored with tiles, matches or tapers from the same lesson, and those belong nowhere near it. If it is old or undated, as most of this stock is, do not open or move it, and arrange a specialist assessment.

How to tell it has deteriorated

What you often see first is green. Bright orange crystals in an old jar may have fine green flakes on the shelf, the lid or among the crystals, left from an earlier demonstration in which some was heated and decomposed. Those flakes are chromium(III) oxide. They show the jar has been used and possibly returned with residues in it, so its contents are no longer pure. A corroded cap, an orange stain on the label and caking from damp are the other usual findings. Paper, wood splinters or match ends in the jar are a serious concern. Do not open it, tip it out or sweep up the green dust. Ask for a specialist assessment and report what you can see from outside.

Legacy stock of unknown condition, decomposes vigorously on heating.

How it must be disposed of

This does not go through our standard collection route. It is arranged by manual enquiry, and never goes down the drain or into general waste.

It leaves after a manual enquiry, because this site does not quote for it online and the online quote path does not accept it. Old stock may be sensitive and is of unknown condition, so a competent chemist needs to see it in person, and a store assessment is recommended. A warning sign may bring in an explosives or emergency specialist. List the jar, any residues kept from past demonstrations, and anything from the same box. Do not open it, move it or try to make it safe, and do not run a final demonstration to use it up. It must never go into a sink, a drain, a bin or a skip. School stock normally takes code 16 05 06*.

Waste codes and transport details for Ammonium dichromate
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.
Show 9 more
  • 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: legacy stock.

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.
  • H312 Harmful in contact with skin.
  • H314 Causes severe skin burns and eye damage.
  • H317 May cause an allergic skin reaction.
  • H330 Fatal if inhaled.
  • H334 May cause allergy or asthma symptoms or breathing difficulties if inhaled.
  • H340 May cause genetic defects.
  • H350 May cause cancer.
  • H360FD May damage fertility. May damage the unborn child.
  • H372 Causes damage to organs through prolonged or repeated exposure.
  • H410 Very toxic to aquatic life with long lasting effects.
Precautionary statements
  • P203 Obtain, read and follow all safety instructions before use.
  • 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.
  • P233 Keep container tightly closed.
  • P260 Do not breathe dust, fume, gas, mist, vapours or spray.
  • P261 Avoid breathing dust, fume, gas, mist, vapours or spray.
  • P264 Wash hands and exposed skin thoroughly after handling.
  • P270 Do not eat, drink or smoke when using this product.
  • P271 Use only outdoors or in a well-ventilated area.
  • P272 Contaminated work clothing should not be allowed out of the workplace.
  • P273 Avoid release to the environment.
  • P280 Wear protective gloves, protective clothing, eye protection and face protection.
  • P284 In case of inadequate ventilation wear respiratory protection.
  • P301+P316 IF SWALLOWED: Get emergency medical help immediately.
  • P301+P330+P331 IF SWALLOWED: Rinse mouth. Do NOT induce vomiting.
  • P302+P352 IF ON SKIN: Wash with plenty of water.
  • 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.
  • P317 Get medical help.
  • P318 If exposed or concerned, get medical advice.
  • P319 Get medical help if you feel unwell.
  • P320 Specific treatment is urgent (see supplemental first aid instruction on this label).
  • P321 Specific treatment (see supplemental first aid instruction on this label).
  • P330 Rinse mouth.
  • P333+P317 If skin irritation or rash occurs: Get medical help.
  • P342+P316 If experiencing respiratory symptoms: Get emergency medical help immediately.
  • P362+P364 Take off contaminated clothing. And wash it before reuse.
  • P363 Wash contaminated clothing before reuse.
  • P370+P378 In case of fire: Use suitable extinguishing media to extinguish.
  • P391 Collect spillage.
  • P403 Store in a well-ventilated place.
  • P403+P233 Store in a well-ventilated place. Keep container tightly closed.
  • 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 do one last volcano demonstration to use up the jar?

No. Old stock is of unknown condition, it decomposes vigorously on heating, and it may cause cancer and is fatal if inhaled. A last demonstration creates the very exposure you are trying to end. Leave the jar closed and send a manual enquiry.

What are the green flakes in and around our jar?

They are chromium(III) oxide, left when some of the salt has been heated and has decomposed, usually at a past demonstration. They show that the jar has been used and may contain mixed residues. Avoid sweeping or wiping them, and mention them in your enquiry.

Does a clean, unopened jar still need an enquiry?

Yes. The route is the same however it looks, because old stock cannot be judged from a web form and the hazards stay with the salt. A clean jar may be a simpler job, so say that it appears unopened and give any date you have.

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 Cr2H8N2O7. EC number 232-143-1.

Manual enquiry Add to register
Search the chemical database