Thiourea (CAS 62-56-6): storage and disposal
Thiourea is a white crystalline solid held in school, college and university stores. It is harmful if swallowed, suspected of causing cancer, suspected of damaging the unborn child and toxic to aquatic life with long lasting effects. The sulfur in it makes it a candidate for reactions with oxidising stock on the same shelf, and in a teaching store a jar can sit unopened for many years.
- CAS number
- 62-56-6
- Form
- Solid
- Storage class
- Toxic
- Signal word
- Warning
- Usual EWC code
- 16 05 06*
Harmful or irritant
Serious health hazard
Hazardous to the environment
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 toxic 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
Teaching stores usually keep thiourea among the sulfur-containing reagents, and it should be sorted out from there. Use a locked cabinet with a stock record, away from food and drink areas, and keep it clear of acids and oxidisers, because toxic stock and oxidising stock are stored apart since a reaction could release hazardous vapours, and several toxic salts give off gas in contact with acid. Keep the lid tight and the jar dry. Because it is suspected of causing cancer and damaging the unborn child, staff handling it need to know the classification. Put the jar on a tray.
How to tell it has deteriorated
Look at the container and label first. Old jars of thiourea may show a yellowish tint where the crystals have been exposed to air and light, caking if damp has got in, and a faint sulfur or ammonia smell on opening. Other signs are a faded or stained label, powder on the cap thread, a cracked jar and a stock record that no longer matches. Because the solid does not change much, a jar with an illegible label or no receipt date is the more common problem than any sign in the crystals. Treat any jar that is discoloured or damp as aged stock.
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 toxic laboratory pack with compatible chemicals.
Waste code 16 05 06* is the usual description for a laboratory holder, and 16 05 08* applies for a discarded organic chemical outside a pack. The point that decides the handling is the aquatic toxicity combined with the cancer classification, so it is never washed into a sink or drain and never put in the bin, and nobody should dissolve or treat it first. Record the jar weight, the condition of the crystals and the lid, and the full label name. It goes in a lab pack with compatible solids, kept apart from acids and oxidising stock, to a permitted facility.
| EWC code, laboratory chemicals | 16 05 06* |
|---|---|
| Discarded organic chemical, not a laboratory pack | 16 05 08* |
| Hazardous waste | Yes |
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
- 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 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
Hazard statements
- H302 Harmful if swallowed.
- H351 Suspected of causing cancer.
- H361d Suspected of damaging the unborn child.
- H411 Toxic to aquatic life with long lasting effects.
Precautionary statements
- P203 Obtain, read and follow all safety instructions before use.
- P264 Wash hands and exposed skin thoroughly after handling.
- P270 Do not eat, drink or smoke when using this product.
- P273 Avoid release to the environment.
- P280 Wear protective gloves, protective clothing, eye protection and face protection.
- P301+P317 IF SWALLOWED: Get medical help.
- P318 If exposed or concerned, get medical advice.
- P330 Rinse mouth.
- P391 Collect spillage.
- 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 thiourea has turned yellow. Is it still usable?
A yellow tint shows it has been exposed to air and light. We would not use it for teaching. Keep the lid tight, label it as aged stock and list it for collection.
Why can thiourea residue not be rinsed away?
It is toxic to aquatic life with long lasting effects, so a drain is never a route, and rinsing a jar out is not allowed. Keep residue in the jar, tightly closed, and leave it for specialist collection.
Can thiourea be stored near nitric acid?
No. Toxic stock and acids are stored apart, and oxidisers react with this class of stock. Keep it in the locked cabinet with a stock record and keep acids in a corrosive store.
What do we tell the collector about an old jar?
The full label name, jar weight, condition of the crystals and lid, and whether any smell or caking is present. That lets the collector pack it correctly with compatible solids.
