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

Ammonium iron(II) sulfate (CAS 10045-89-3): storage and disposal

Ferrous ammonium sulfate, usually held as the hexahydrate, is a pale crystalline solid found in school prep rooms, college stores and university teaching labs. It is not classified as hazardous on the sources we checked, but it is still a chemical waste and must be described accurately. What decides its handling is the waste code, 16 05 09, and whether the bottle still holds clean, dry crystals or stock that has visibly changed.

CAS number
10045-89-3
Form
Solid
Storage class
General
Usual EWC code
16 05 09

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 general 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

Ordinarily this salt sits in a school prep room on a general shelf alongside the other iron and ammonium salts, in a tightly closed bottle with a date on the label. It is general class stock, so a dry, labelled, well organised store suits it, dated on arrival. Keep the cap on between uses, because the crystals slowly react with air, and keep the bottle away from food grade supplies. Colleges and universities that issue it for redox titration practicals should return part-used bottles to the store shelf rather than leave them on a teaching bench, where lids go missing and the crystals pick up moisture and dust.

How to tell it has deteriorated

Good stock is pale blue-green crystals that run freely. An aged bottle shows yellow or brown staining across the crystal surfaces, because the iron(II) in it oxidises to iron(III) once air gets in. Brown crust around the neck, caking, a damp lump at the base or a cap that has seized all point to a poor seal or moisture getting into the bottle. The general checks apply too: a faded label and an unknown date of receipt. Stock that has gone brown is still chemical waste. Set it aside and label it, and do not tip it back into a working bottle or mix it with fresh crystals.

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 non-regulated or low hazard laboratory pack with compatible chemicals.

The entry used for this item is waste code 16 05 09, a code for chemicals that are not classed as hazardous waste. That does not make it a free for all. It does not go into a sink, a drain, a general waste bin or a skip, and nobody should try to treat it first. It leaves through specialist collection, packed with compatible stock into a lab pack. A waste transfer note travels with it, so the label should carry the full name, the hexahydrate form where that is what the bottle holds, and a rough idea of how much remains. Brown, oxidised stock is described in the same way as fresh stock, with a note of its condition.

Waste codes and transport details for Ammonium iron(II) sulfate
EWC code, laboratory chemicals16 05 09
Hazardous wasteNo

The code depends on where the waste came from and what it is mixed with. Use the waste code finder to see why.

Common quantities we collect

Usually held as: hexahydrate.

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

Questions

Can brown, oxidised ammonium iron(II) sulfate still be collected?

Yes. Colour change does not stop it going through specialist collection. It is described as the same substance, with its condition noted on the label, and packed with compatible stock. Keep it in its own closed container, and do not combine it with fresh crystals.

Is it hazardous waste?

It is not classified as hazardous on the sources we checked, and the waste code is 16 05 09. It is still a chemical waste, so it needs an accurate description and a waste transfer note. The supplier safety data sheet for your own stock remains the reference.

Why does the salt in our bottle look yellow at the surface?

Air slowly oxidises the iron(II) in the crystals to iron(III), which gives the yellow to brown staining. A tight cap and a dry shelf slow this down. A bottle that is mostly brown, caked or damp is better dated, labelled and put forward for collection than topped up.

How long can a teaching department keep an opened bottle?

No fixed period is set for this item. Date it on arrival, check the crystals each term for colour, caking and a sound cap, and put forward any bottle that has changed noticeably or lost its date.

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 FeH8N2O8S2. EC number 233-151-8.

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