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

Barium sulfate (CAS 7727-43-7): storage and disposal

Barium sulfate is a dense white solid that turns up in two very different places: as a laboratory powder in school, college and university stores, and as radiography contrast stock in pharmacies. It is not classified as hazardous on the sources we checked, yet it remains a chemical waste that needs an accurate description. Holders must work out first which of the two they are dealing with.

CAS number
7727-43-7
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

Radiography contrast is the item that gets mislaid. Pharmacy tubs and sachets are held with medicines and follow the pharmacy's own stock control, with expiry dates checked as for any other product. The laboratory powder belongs on a general shelf in a dry, labelled store, dated on arrival and kept away from food grade supplies. Because the powder is very fine and dense, a loose lid lets it spread as white dust on the shelf and over neighbouring bottles. In a school prep room it often sits next to the barium chloride used for sulfate tests, and the two bottles should be clearly different on the label.

How to tell it has deteriorated

The powder itself changes very little. A tub that was fine and free-flowing years ago looks the same now, so the container is the thing to read. White dust around a lid shows a poor seal, clumping means damp has got in, and a faded label or no date of receipt are the usual faults. Contrast products are different because they have printed expiry dates, and sachets or tubs that are split, swollen or past their date should be put aside with their packaging. In a school store the real risk is confusion with barium chloride from a smudged label, not any visible change.

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.

Contrast stock changes the description. A hospital pharmacy should check with its responsible pharmacist whether medicines arrangements apply, because out-of-date contrast products are not listed like loose laboratory powder. The entry for laboratory powder is 16 05 09 and the healthcare entry is 18 01 07, and neither is a hazardous waste entry. It remains chemical waste and must be described accurately. It must not go into a sink, a drain, general waste or a skip, and nobody should try to treat it first. Give each container's form as powder or contrast product, and keep original packaging on contrast items with the expiry date visible.

Waste codes and transport details for Barium sulfate
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, radiography contrast.

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 barium sulfate classified as hazardous?

It is not classified as hazardous on the sources we checked. It is still a chemical waste, so it needs an accurate description and specialist collection. Keep it clearly labelled and apart from soluble barium salts such as the chloride.

Do out-of-date contrast products go in a lab collection?

They are described as medicinal contrast products, with expiry dates noted. A pharmacy should speak to its responsible pharmacist first, to confirm whether its own medicines arrangements apply before the stock joins any collection.

How do we avoid mixing it up with barium chloride?

Give each its own clear, dated label, shelve them apart and record both in the stock list. The two salts are both white powders, and a smudged label is the usual cause of confusion in school stores.

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 BaO4S. EC number 231-784-4.

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