Ammonium sulfate (CAS 7783-20-2): storage and disposal

Ammonium sulfate is a white crystalline salt held in school, college, university and pathology stores, used for fertiliser demonstrations and for precipitating proteins. It is not classified as hazardous on the sources we checked, but it remains a chemical waste that must be described accurately. Bleach and strong alkalis, not the salt itself, are the shelf problem.

CAS number: 7783-20-2
Form: Solid
Storage class: General
Usual EWC code: 16 05 09

What to do this week

Check the label is readable and write down the opened date if it is not already there.
Check it is stored as general stock and apart from the items listed under "Do not store with".
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

No classified hazard decides where it goes, but the neighbours do. Keep it away from hypochlorites, chlorine releasing stock and chloramine type disinfectants, since ammonium salts and hypochlorites form toxic chloramine gases, and from chlorates and hydroxides. A school prep room that keeps it beside the bleach or a bottle of caustic soda should separate them. Otherwise a dry, labelled, well organised store, dated on arrival, is enough, and garden grade or food supplies in the same room should stay apart from laboratory stock. Not being classified as hazardous on the sources we checked does not remove the need for a stock record.

How to tell it has deteriorated

What a technician sees first is a tub of white crystals or powder that should tip freely. Damp air makes it cake into a lump and leaves a crust around the neck. The salt gives few distinctive signs of its own, so look at the container: a cracked tub, a faded or lifted label, a lid that no longer closes and no date of receipt. A sharp smell of ammonia on opening is not normal and suggests it has met an alkali nearby. Record the condition as found, and close the tub and report it if it smells.

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.

Fertiliser grade and laboratory grade tubs should be told apart on the list, because a garden sack may carry other ingredients. Hypochlorites, chlorates and hydroxides are kept out of its group, since ammonium salts react with them. For a laboratory the code is 16 05 09, and a pathology lab in human healthcare would quote 18 01 07. Though not classified as hazardous on the sources we checked, it is still chemical waste, so a sink, drain, bin or skip is ruled out and nobody should try to treat it first. Transfer note paperwork is enough for the movement. Give the full name, the tub size and roughly what is left, and the collector will place it with other low hazard solids.

Waste codes and transport details for Ammonium sulfate
EWC code, laboratory chemicals	16 05 09
Human healthcare setting	18 01 07
Hazardous waste	No

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

Named chemicals to keep apart

Calcium hypochloriteHypochlorites and ammonia or amines form toxic chloramine gases.
Chloramine THypochlorites and ammonia or amines form toxic chloramine gases.
Potassium chlorateChlorates and ammonium salts can form unstable ammonium chlorate.
Potassium hydroxideStrong alkalis release ammonia gas from ammonium salts.
Sodium chlorateChlorates and ammonium salts can form unstable ammonium chlorate.
Sodium dichloroisocyanurateHypochlorites and ammonia or amines form toxic chloramine gases.
Sodium hydroxideStrong alkalis release ammonia gas from ammonium salts.
Sodium hypochloriteHypochlorites and ammonia or amines form toxic chloramine gases.

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Sodium nitriteNitrites and ammonium salts can react violently on heating.

Common quantities we collect

Usually held as: solid.

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

Is ammonium sulfate hazardous waste?

It is not classified as hazardous on the sources we checked, so a waste transfer note applies. It is still a chemical waste that must be described accurately and collected by the specialist route.

Why keep it away from bleach?

Hypochlorites and ammonia or amines form toxic chloramine gases, and ammonium salts count. Keep the salt on a separate shelf from bleach, chlorine tablets and chlorates.

We hold garden grade sulfate of ammonia. Does that matter?

Say so when you describe the stock, with the bag or tub size. Keep it labelled and apart from food grade supplies and from laboratory stock until it is collected.

Which waste code applies in a pathology lab?

A human healthcare setting may use 18 01 07, and a school or university lab 16 05 09. Say which setting the stock sits in when you ask for collection.