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

2,4-Dinitrophenylhydrazine (CAS 119-26-6): storage and disposal

2,4-Dinitrophenylhydrazine, or 2,4-DNPH, is the orange-red solid behind Brady's reagent, the classic carbonyl test in school and college chemistry. It is sold damp for a good reason: dry material is sensitive to friction and shock. Prep rooms and university stores often hold an old tub or some reagent stock based on it. Whether the contents have stayed damp decides everything that follows.

CAS number
119-26-6
Form
Solid
Storage class
Flammable
Signal word
Danger
Usual EWC code
16 05 06*
  • Flammable pictogramFlammable
  • Harmful or irritant pictogramHarmful or irritant

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.

Flammable and explosive if allowed to dry.

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

Drying out is the hazard that decides where it goes. Sound stock counts as a flammable solid and goes in a fire-resistant cabinet, away from ignition sources and oxidisers, and apart from acids, with the lid firmly on and the label readable. Warm spots matter here more than for most flammable stock, since a shelf near a radiator or a sunny window helps the water leave. Keep it low down, somewhere it will not get knocked. Check the date on arrival and look at it during every stocktake, because tubs like this get pushed to the back and forgotten. Any tub that has already lost its condition is another matter: leave it exactly as found and never try to top it up with water.

How to tell it has deteriorated

Look at the outside of the container before anything else, and do not touch it while you look. Crystals in the cap threads are the main warning, as turning that lid would grind them. Dry contents are the other: a loose, free running powder where there should be a damp cake. Orange crusting around the neck of a reagent bottle, or a level that has dropped, suggests liquid has evaporated and left solid behind. A faded label or no date of receipt means nobody can vouch for its history. If it is old, undated or shows any of these signs, do not move it and do not open it. It needs a specialist assessment in person.

Supplied damp. Becomes a friction and shock risk when it dries out.

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.

Before asking for a collection, record what can be seen without touching: the label wording, the container size, any date, crystals on the threads and whether the contents look dry. A photograph taken from a distance helps. This item goes by manual enquiry. It is not quoted online and does not go through the quote path, and a store assessment is recommended. A competent chemist has to judge it in person, and where a warning sign is present it may need an explosives or emergency specialist. List any reagent stock on the same enquiry. Nobody should open the tub, move it or add water in an attempt to make it safe while waiting for advice.

Waste codes and transport details for 2,4-Dinitrophenylhydrazine
EWC code, laboratory chemicals16 05 06*
Discarded organic chemical, not a laboratory pack16 05 08*
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

  • OxidiserOxidisers can ignite flammable materials or make a fire far more intense.
  • AcidOxidising acids can ignite flammable materials, and acid fumes attack containers and seals.
  • CorrosiveA leak of corrosive stock can break down flammable containers and feed a fire.

Named chemicals to keep apart

  • Acetic acidOxidising acids can ignite flammable materials, and acid fumes attack containers and seals.
  • Calcium hypochloriteOxidisers can ignite flammable materials or make a fire far more intense.
  • Hydrochloric acidOxidising acids can ignite flammable materials, and acid fumes attack containers and seals.
  • Hydrogen peroxideOxidisers can ignite flammable materials or make a fire far more intense.
  • Nitric acidOxidising acids can ignite flammable materials, and acid fumes attack containers and seals.
  • Potassium nitrateOxidisers can ignite flammable materials or make a fire far more intense.
  • Potassium permanganateOxidisers can ignite flammable materials or make a fire far more intense.
  • Sulfuric acidOxidising acids can ignite flammable materials, and acid fumes attack containers and seals.
Show 2 more
  • Thionyl chlorideA leak of corrosive stock can break down flammable containers and feed a fire.
  • Zinc chlorideA leak of corrosive stock can break down flammable containers and feed a fire.

Common quantities we collect

Usually held as: damp solid, Brady reagent 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

  • H228 Flammable solid.
  • H302 Harmful if swallowed.
  • H319 Causes serious eye irritation.
Precautionary statements
  • P210 Keep away from heat, hot surfaces, sparks, open flames and other ignition sources. No smoking.
  • P240 Ground and bond container and receiving equipment.
  • P241 Use explosion-proof electrical, ventilating and lighting equipment.
  • P264 Wash hands and exposed skin thoroughly after handling.
  • P264+P265 Wash hands and exposed skin thoroughly after handling. Do not touch eyes.
  • P270 Do not eat, drink or smoke when using this product.
  • P280 Wear protective gloves, protective clothing, eye protection and face protection.
  • P301+P317 IF SWALLOWED: Get medical help.
  • P305+P351+P338 IF IN EYES: Rinse cautiously with water for several minutes. Remove contact lenses, if present and easy to do. Continue rinsing.
  • P330 Rinse mouth.
  • P337+P317 If eye irritation persists: Get medical help.
  • P370+P378 In case of fire: Use suitable extinguishing media to extinguish.
  • P501 Dispose of contents and container in accordance with local, regional, national and international regulations.

Substance as classified, dilutions may differ.

Questions

Can we add water to a tub that looks as though it has dried out?

No. Opening the lid is itself the risk if crystals have formed in the threads, and rewetting counts as trying to make it safe. Leave the tub where it is, keep people away from it and send us an enquiry describing what you can see.

Does the same caution apply to a bottle of Brady's reagent?

Treat it with care if the bottle is old, the level has fallen or solid has appeared around the neck, because evaporation can leave the dry solid behind. Describe it in the same enquiry. Do not try to clean the neck or loosen the cap.

Should we clear the prep room if we find crystals round the lid?

Keep people out of the immediate area and stop any work that might knock the shelf. Crystals in the threads are a warning sign, so an explosives or emergency specialist may be needed. Tell your senior science or safety lead straight away, and send the enquiry.

How often should a damp tub be looked at while we still hold it?

Include it in every routine stocktake, and look without opening. If nobody uses it any more, that is a good reason to raise an enquiry rather than go on checking it, since the risk comes from it being forgotten as it slowly dries.

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 C6H6N4O4. EC number 204-309-3.

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