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

Sodium dichromate (CAS 10588-01-9): storage and disposal

Orange-red crystals of sodium dichromate, usually the dihydrate, sit in school, college and university stores as a chromium(VI) oxidiser. It may cause cancer and genetic defects, is fatal if inhaled and can intensify a fire. Unlike its potassium cousin it readily absorbs moisture, so an old jar can look wet, and that is often how it first draws attention. The chromium(VI) content and that dampness decide how it is stored and described when it leaves.

CAS number
10588-01-9
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

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

A school prep room normally keeps it in the oxidiser space, apart from flammable and toxic stock, and moisture is what makes its position awkward. Because the salt pulls water from the air, a damp outside wall or a busy wash-up area soon shows in the jar. Keep the lid closed firmly, and check whether a paper label has started to soften or stain. Non-combustible shelving matters more than usual here, since wet salt creeping onto a wooden shelf leaves an oxidiser in the grain as it dries. Activated charcoal, aluminium powder and glucose can form mixtures with it that burn fiercely or explode. Diethyl ether, diisopropyl ether, 1,4-dioxane and hydrazine hydrate must also stay well away from this store.

How to tell it has deteriorated

Orange staining on the label and around the cap usually comes first, because wet salt creeps outward from a poor seal. A sticky bottle, a corroded cap or softened paper all point the same way. Inside the jar, sound crystals are orange-red and separate. Moisture makes them clump and then look wet, which is common with this salt but still shows the seal has failed. A green tinge means some chromium(VI) has been reduced to chromium(III), usually where it has met organic matter such as a dirty spatula or paper fibres. Any of that deserves a careful description and no more. Do not scrape the neck or open a sticky jar to look, because dried dust is the form most easily breathed in.

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.

It must never reach a sink, a drain, a general waste bin or a skip, and nobody should try to reduce or otherwise treat it first. Its long lasting toxicity to aquatic life is reason enough. Drying a wet looking jar or tipping it into a fresh one is also out, because that is when dust and spills happen. Specialist collection is the only route. Describe it by its full name, as dihydrate if the label says so, and make clear it is the sodium salt, because the label is easily confused with potassium dichromate. Say whether the contents look damp. In the collection it goes with oxidisers, apart from solvents and other organics. A damp jar should be flagged in advance so it can be packed accordingly.

Waste codes and transport details for Sodium 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

  • 1,2-DimethoxyethanePeroxide forming ethers can ignite or explode with strong oxidisers.
  • 1,4-DioxanePeroxide forming ethers can ignite or explode with strong oxidisers.
  • 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.
  • Activated charcoalStrong oxidisers can form mixtures with these materials that burn fiercely or explode.
  • Aluminium powderStrong oxidisers can form mixtures with these materials that burn fiercely or explode.
  • Ammonia solutionSome oxidisers react strongly with alkalis, and ammonia based stock is especially at risk.
  • Diethyl etherPeroxide forming ethers can ignite or explode with strong oxidisers.
Show 14 more
  • Diisopropyl etherPeroxide forming ethers can ignite or explode with strong oxidisers.
  • 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.
  • GlucoseStrong oxidisers can form mixtures with these materials that burn fiercely or explode.
  • 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.
  • Magnesium ribbonStrong oxidisers can form mixtures with these materials that burn fiercely or explode.
  • Potassium cyanideCyanides react violently with strong oxidisers.
  • Red phosphorusStrong oxidisers can form mixtures with these materials that burn fiercely or explode.
  • Sodium cyanideCyanides react violently with strong oxidisers.
  • SucroseStrong oxidisers can form mixtures with these materials that burn fiercely or explode.
  • SulfurStrong oxidisers can form mixtures with these materials that burn fiercely or explode.
  • TetrahydrofuranPeroxide forming ethers can ignite or explode with strong oxidisers.
  • White phosphorusPhosphorus can ignite or explode with oxidisers.

Common quantities we collect

Usually held as: dihydrate.

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

Our sodium dichromate looks wet. Has it gone off?

It has absorbed moisture from the air, which this salt does readily, so the wet look says more about the seal than the chemical. It is still chromium(VI) with the same long term hazards. Leave the jar closed and mention the wet appearance when arranging collection.

Can we combine the remains of several old jars to save space?

No. Tipping one into another creates dust, mixes unknown contamination and gives you a container that no longer matches any label. Each jar should stay as it is, listed separately with its own wording and condition, and packing can then be sorted out at collection.

Can it share a shelf with our potassium dichromate?

Yes, both belong in the same oxidiser space. The sodium salt is the one more likely to weep, so give it a resistant tray of its own to catch anything creeping from the neck, and keep both labels clear so the two are not confused on a stock list.

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 Cr2Na2O7. EC number 234-190-3.

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