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

Phosphorus pentoxide (CAS 1314-56-3): storage and disposal

Phosphorus pentoxide turns up in school, college and university stores as a drying agent for desiccators, and as old jars left by earlier staff. It causes severe skin burns and eye damage and reacts violently with water. Because it pulls moisture from anything near it, old stock changes in a way that makes the jar itself the best clue to its condition.

CAS number
1314-56-3
Form
Solid
Storage class
Corrosive
Signal word
Danger
Usual EWC code
16 05 06*
  • Corrosive pictogramCorrosive

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 corrosive 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

Violent reaction with water decides where this powder can live. It needs a resistant tray low down in a ventilated corrosive store, with a tight lid and a dry space around it, and well away from ammonia solution, formalin, hydrochloric acid, hydrogen peroxide, sodium hydroxide, sodium hypochlorite and any other water based stock. Oxidisers and solvent cabinets are also kept clear in line with the corrosive class. A desiccator in use counts as storage too: the lid should be kept on, and the desiccator kept on a bench away from wet work, because it takes water from the air each time it is opened.

How to tell it has deteriorated

Fresh material is a white, light powder that moves freely in its jar. Old material forms a sticky, glassy crust, and that crust is the principal sign, usually first on the surface where air has reached it, then spreading downward as the powder takes up moisture. A used desiccator charge looks wet and syrupy rather than dry. Check as well for a cap that has fused to the neck, corrosion around the closure, pitted shelving and labels that have lifted or stained. A jar with a hard crust or a stuck lid should not be forced or scraped. Leave it where it is, closed, and say what you see when asking for a collection.

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 corrosive other laboratory pack with compatible chemicals.

Record where the material is held, whether in the original jar or a desiccator dish, how much remains, and whether a crust or fused cap is present. Those details tell the packer how awkward the job is. Anything left in a desiccator is not tipped out to tidy it up: water must never be added, and nobody should wash the dish or neutralise the residue. The jar travels in a lab pack grouped with compatible solids under 16 05 06*, or under 16 05 07* if it is a discarded inorganic chemical outside one. Specialist collection is the only route.

Waste codes and transport details for Phosphorus pentoxide
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

  • FlammableA leak of corrosive stock can break down flammable containers and feed a fire.
  • OxidiserCorrosive stock can react with oxidisers, releasing heat or fumes.

Named chemicals to keep apart

  • AcetoneA leak of corrosive stock can break down flammable containers and feed a fire.
  • Ammonia solutionReacts with water, releasing heat and often a flammable or corrosive gas, so keep it away from all water based stock.
  • Calcium hypochloriteCorrosive stock can react with oxidisers, releasing heat or fumes.
  • EthanolA leak of corrosive stock can break down flammable containers and feed a fire.
  • FormalinReacts with water, releasing heat and often a flammable or corrosive gas, so keep it away from all water based stock.
  • HexaneA leak of corrosive stock can break down flammable containers and feed a fire.
  • Hydrochloric acidReacts with water, releasing heat and often a flammable or corrosive gas, so keep it away from all water based stock.
  • Hydrogen peroxideReacts with water, releasing heat and often a flammable or corrosive gas, so keep it away from all water based stock.
Show 6 more
  • MethanolA leak of corrosive stock can break down flammable containers and feed a fire.
  • Potassium nitrateCorrosive stock can react with oxidisers, releasing heat or fumes.
  • Potassium permanganateCorrosive stock can react with oxidisers, releasing heat or fumes.
  • Sodium hydroxideReacts with water, releasing heat and often a flammable or corrosive gas, so keep it away from all water based stock.
  • Sodium hypochloriteReacts with water, releasing heat and often a flammable or corrosive gas, so keep it away from all water based stock.
  • TolueneA leak of corrosive stock can break down flammable containers and feed a fire.

Common quantities we collect

Usually held as: desiccant, 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

  • H314 Causes severe skin burns and eye damage.

Substance as classified, dilutions may differ.

Questions

Our old jar has a hard glassy crust. Can we chip it off so the lid opens?

No. Forcing the lid or breaking the crust exposes fresh powder to moist air and to skin. Keep the jar shut, stand it on a tray in a dry corrosive store and describe the crust when you book collection.

What do we do with the spent charge still in a desiccator?

Leave it in place with the lid on and tell the collection team it is there. Do not add water, wash the dish or empty the desiccator in the prep room. The whole assembly can be described and packed as found.

Why can it not sit beside our aqueous reagents?

It reacts violently with water, so any leak or spill from water based bottles nearby could set it off, releasing heat. It needs a dry corrosive store of its own, away from solutions of acids, alkalis and peroxide.

Does the powder have a shelf life?

It keeps only while it stays dry and sealed. Every opening lets in moist air, so heavily used jars crust sooner. Date it on arrival and check the lid and surface at each stock take.

Guidance only. Check your own risk assessment and your supplier's safety data sheet.

Hazard data source: GB mandatory classification list (HSE), retrieved 31 Oct 2026. Formula O5P2.

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