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

Sudan III (CAS 85-86-9): storage and disposal

A fat-soluble red dye that colours oils and fats rather than water, Sudan III is used in school and college practicals on food tests, and in pathology and histology for lipids. It is held as powder, often in a jar bought many years ago. It is not classified as hazardous on the sources we checked, but it remains a chemical waste, and its stain-everything habit is what holders notice first.

CAS number
85-86-9
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

School prep rooms hold Sudan III beside the food test reagents, which is where it should stay apart from iodine, Benedict's and other practical stock that belongs to different tests. Colour is no help when labels fail, since several red and orange fat-soluble dyes look much alike in the jar. It is general stock, so a dry, labelled shelf is sufficient. Because it stains oil, plastic and skin rather than washing off with water, store it on a tray in a closed jar with the date of receipt on the side. Any working solution made up for a practical needs its own label and date.

How to tell it has deteriorated

Red dust on the lid, on the shelf or on the neighbouring bottles is the first thing to find, because this dye is a fine powder that creeps. Sound powder is dry and loose behind a clean thread. If it has caked, clumped or looks damp, moisture has been getting in. The dye gives few other visible signs of age, so the evidence is on the jar: a faded or stained label, a cracked container, no date of receipt or a stock record that no longer agrees. Where the label is gone, red colour cannot tell Sudan III from its neighbours, so the jar is listed as unknown stock and left unopened.

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.

Prep room or lab store stock goes down on the request as 16 05 09, and a human healthcare service clearing it as 18 01 07. Record the form, the jar size and any damage, and mention whether any prepared solutions made in the school or lab are in the same cupboard, as those are different containers. It is not classified as hazardous on the sources we checked, but it is still a chemical waste that has to be described accurately, so it is never put in a sink, a drain or a skip and no one should try to clean or treat the jar first.

Waste codes and transport details for Sudan III
EWC code, laboratory chemicals16 05 09
Human healthcare setting18 01 07
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: 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 Sudan III dangerous enough to need special handling?

It is not classified as hazardous on the sources we checked, but it is still a chemical waste that needs an accurate description. A dry, labelled shelf is enough, and it must not go into general waste.

Can we tell Sudan III from Sudan IV by looking at the jar?

Not reliably. Several red fat-soluble dyes look alike, so rely on the label and the stock record. Where either is lost, list the jar as unknown rather than guessing.

What if a solution made for a practical is still in the cupboard?

List it as its own item with the container size and, if known, the solvent used. A prepared solution is not described by the powder jar's label and may be classed differently.

Which code applies in a school?

A school, college or laboratory store uses 16 05 09 for this dye. Human healthcare services clearing stock use 18 01 07, so the setting should be stated on the request.

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 C22H16N4O. EC number 201-638-4.

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