Thallium (CAS 7440-28-0): storage and disposal
Thallium metal is mostly a university holding, and most of what remains is legacy stock in small containers from past research. It is a very toxic metal, fatal if swallowed or inhaled, and it is absorbed through skin. Because it is soft and tarnishes grey, it is easy to mistake for lead or another dull metal. What decides handling is a reliable identification, followed by a locked place and careful packing.
- CAS number
- 7440-28-0
- Form
- Solid
- Storage class
- Toxic
- Signal word
- Danger
- Usual EWC code, laboratory stock
- 16 05 06*
Acute toxicity
Serious health hazard
What to do this week
- Without moving anything that looks damaged, check the label is readable and write down the opened date if it is not already there.
- Check it is stored as toxic stock, and apart from anything listed under "Do not store with" on this page. If nothing is listed, that does not prove it is safe with everything.
- If you no longer need it, add it to your disposal list so it can be included in a collection.
Safe storage in a school or lab
Small sealed bottles or ampoules are the usual form, sometimes with the metal under oil. Leave any such arrangement as it stands, because exposure to air only adds to the tarnish and opening the container brings no benefit. A locked toxic cabinet with a stock record is the right home, with acids and oxidisers in their own stores. Absorption through skin sets it apart from most metals in a university collection. The metal is soft enough to leave traces on gloves or on a shelf, so anyone handling the outside of a dirty container needs to treat that surface as contaminated. Departments with several research groups should check that a named person holds the record, because legacy stock tends to outlive those who bought it.
How to tell it has deteriorated
A faded label or one with only the symbol Tl is the most common problem, as old research stock often carries little else. Check the cap and any seal for damage, and look for grey smears around the neck or on the shelf beneath. The metal itself tarnishes grey in air, so a dull surface is expected and does not show that anything is wrong. Where it was kept under oil, a low level means more of it has been reaching the air. Otherwise it gives few visual signs, and age alone tells you little. Staining around the cap or a lost stock record both deserve attention. Do not open a container to see what is inside it. Describe what you can see from outside.
How it is disposed of
We arrange this by specialist collection. We do not publish a drain or general waste route for any chemical. It is normally packed in a toxic laboratory pack with compatible chemicals.
Before asking for a collection, record the wording on the label, the container type, whether it is under oil or sealed in an ampoule, and the rough quantity. Note any grey smears on the outside, as that affects how the container can be handled when it is packed. If only a symbol survives on the label, say so and do not open it to confirm the contents. Thallium does not go into a sink, a drain, a general waste bin or a skip, and nobody should try to treat it first. Specialist collection is the only route, and the fatal hazards mean it is packed as toxic stock, away from acids and oxidisers. Code 16 05 06* normally fits university stock, though the producer classifies the waste.
| Usual EWC code, laboratory stock | 16 05 06* |
|---|---|
| Discarded inorganic chemical, not a laboratory pack | 16 05 07* |
| Usually classed as hazardous waste | Yes |
The code depends on where the waste came from and what it contains, and classifying it is the producer's duty. Use the waste code finder to see why.
Do not store with
- OxidiserToxic and oxidising stock are stored apart. A reaction could release toxic vapours.
- AcidToxic stock is stored apart from acids. Several toxic salts release toxic gas in contact with acid.
Named chemicals to keep apart
- Acetic acidToxic stock is stored apart from acids. Several toxic salts release toxic gas in contact with acid.
- Calcium hypochloriteToxic and oxidising stock are stored apart. A reaction could release toxic vapours.
- Hydrochloric acidToxic stock is stored apart from acids. Several toxic salts release toxic gas in contact with acid.
- Hydrogen peroxideToxic and oxidising stock are stored apart. A reaction could release toxic vapours.
- Nitric acidToxic stock is stored apart from acids. Several toxic salts release toxic gas in contact with acid.
- Potassium nitrateToxic and oxidising stock are stored apart. A reaction could release toxic vapours.
- Potassium permanganateToxic and oxidising stock are stored apart. A reaction could release toxic vapours.
- Sulfuric acidToxic stock is stored apart from acids. Several toxic salts release toxic gas in contact with acid.
Common quantities
Usually held as: legacy stock.
Tell us the container size and how many you hold. An estimate is enough to start with, and some items cannot be priced until someone has looked at them.
Where it is commonly held
Hazard statements
- H300 Fatal if swallowed.
- H330 Fatal if inhaled.
- H373 May cause damage to organs through prolonged or repeated exposure.
- H413 May cause long lasting harmful effects to aquatic life.
Precautionary statements
- P260 Do not breathe dust, fume, gas, mist, vapours or spray.
- P264 Wash hands and exposed skin thoroughly after handling.
- P270 Do not eat, drink or smoke when using this product.
- P271 Use only outdoors or in a well-ventilated area.
- P273 Avoid release to the environment.
- P284 In case of inadequate ventilation wear respiratory protection.
- P301+P316 IF SWALLOWED: Get emergency medical help immediately.
- P304+P340 IF INHALED: Remove person to fresh air and keep comfortable for breathing.
- P316 Get emergency medical help immediately.
- P319 Get medical help if you feel unwell.
- P320 Specific treatment is urgent (see supplemental first aid instruction on this label).
- P321 Specific treatment (see supplemental first aid instruction on this label).
- P330 Rinse mouth.
- P403+P233 Store in a well-ventilated place. Keep container tightly closed.
- P405 Store locked up.
- P501 Dispose of contents and container in accordance with local, regional, national and international regulations.
Substance as classified, dilutions may differ.
Questions
Our old bottle just says Tl. Can we treat it as thallium without testing it?
Yes, treat it as thallium on the strength of that label, and nobody should open it to test it. State the exact wording and describe the container when you arrange a collection. An honest note that the identification rests on a symbol is more useful than a guess.
The metal has gone dull and grey. Has it degraded?
Thallium tarnishes grey in air, so a dull surface is expected and does not change how it is handled. It stays very toxic under that tarnish. The more useful question is how air got to it, so check for a low oil level or a damaged seal.
Who should keep the record for thallium in a shared university store?
A named person in the department should hold it, with the location, quantity and date of the last check. Legacy thallium often outlasts the research group that bought it, and an ownerless locked bottle is a common finding in a shared store. Any handover should cover it explicitly.
