Potassium cyanide (CAS 151-50-8): storage and disposal
A small locked bottle of potassium cyanide is usually legacy stock in a college or university, left from older teaching or research. It is rapidly fatal by all routes, causes organ damage with repeated exposure and is very toxic to aquatic life. It absorbs moisture, and with moist air or any acid it releases hydrogen cyanide gas. Dry, locked and separated storage, with a firm plan to clear it, decides how it is handled.
- CAS number
- 151-50-8
- Form
- Solid
- Storage class
- Toxic
- Signal word
- Danger
- Usual EWC code
- 16 05 06*
Acute toxicity
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
Hydrogen cyanide release decides the position. Moist air starts it slowly and acid starts it fast, so a poisons cupboard shared with acid salts or standing against a damp wall is a poor home even if the lock is good. Keep hydrochloric, nitric, hydrobromic and perchloric acid in another store altogether, and read the labels on small bottles nearby, since an old poisons cupboard often holds a mix. Calcium hypochlorite, hydrogen peroxide and chromium trioxide must also stay away, as it reacts violently with them. Always locked and dry, with a stock record kept up to date. That record should show quantity and the last date seen, and keys need a formal handover when staff leave. Legacy stock with no named owner is the failure to prevent.
How to tell it has deteriorated
Start with the container and label: a damp outer surface, a stained cap or a faded label on a bottle nobody has opened for years. This salt absorbs moisture, so caked solid is the sign that air has been getting in, and with that comes slow release of hydrogen cyanide. Sound stock is free flowing white granules or lumps. Not everyone can smell cyanide, so a lack of smell around the cupboard offers no reassurance, and nobody should try to smell it on purpose. Mismatch between the stock record and the bottle also counts as a warning. If the container is damp or the solid has caked, do not open it. Keep people out of that room and call for specialist help.
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.
Bleach, acid or any other chemical must never be used on it, and it must not go into a sink, a drain, a general waste bin or a skip. Attempts to destroy it create the very gas it is locked away to avoid. Specialist collection is the only route, and it needs a precise description: name, quantity, solid form, and any caking or damp. Check the bottle against your stock record before you ask, and report any difference. Inside a collection it stays well away from acids and oxidisers, so it should never appear on a list as mixed poisons. Have a key holder available on the day. Colleges and universities normally use code 16 05 06*, and the consignment note should agree with your stock record.
| EWC code, laboratory chemicals | 16 05 06* |
|---|---|
| Discarded inorganic chemical, not a laboratory pack | 16 05 07* |
| 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 hypochloriteCyanides react violently with strong oxidisers.
- Chromium trioxideCyanides react violently with strong oxidisers.
- Hydrobromic acidCyanides release highly toxic hydrogen cyanide gas with acids.
- Hydrochloric acidCyanides release highly toxic hydrogen cyanide gas with acids.
- Hydrogen peroxideCyanides react violently with strong oxidisers.
- Hydroiodic acidCyanides release highly toxic hydrogen cyanide gas with acids.
- Nitric acidCyanides release highly toxic hydrogen cyanide gas with acids.
Show 10 more
- Perchloric acidCyanides release highly toxic hydrogen cyanide gas with acids.
- Phosphoric acidCyanides release highly toxic hydrogen cyanide gas with acids.
- Potassium chlorateCyanides react violently with strong oxidisers.
- Potassium dichromateCyanides react violently with strong oxidisers.
- Potassium nitrateToxic and oxidising stock are stored apart. A reaction could release toxic vapours.
- Potassium permanganateCyanides react violently with strong oxidisers.
- Sodium chlorateCyanides react violently with strong oxidisers.
- Sodium dichromateCyanides react violently with strong oxidisers.
- Sulfuric acidCyanides release highly toxic hydrogen cyanide gas with acids.
- Trichloroacetic acidCyanides release highly toxic hydrogen cyanide gas with acids.
Common quantities we collect
Usually held as: legacy stock.
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
- H300 Fatal if swallowed.
- H310 Fatal in contact with skin.
- H330 Fatal if inhaled.
- H372 Causes damage to organs through prolonged or repeated exposure.
- H410 Very toxic to aquatic life with long lasting effects.
Precautionary statements
- P234 Keep only in original packaging.
- P260 Do not breathe dust, fume, gas, mist, vapours or spray.
- P262 Do not get in eyes, on skin, or on clothing.
- P264 Wash hands and exposed skin thoroughly after handling.
- P264+P265 Wash hands and exposed skin thoroughly after handling. Do not touch eyes.
- 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.
- P280 Wear protective gloves, protective clothing, eye protection and face protection.
- P284 In case of inadequate ventilation wear respiratory protection.
- P301+P316 IF SWALLOWED: Get emergency medical help immediately.
- P302+P352 IF ON SKIN: Wash with plenty of water.
- P304+P340 IF INHALED: Remove person to fresh air and keep comfortable for breathing.
- P305+P354+P338 IF IN EYES: Immediately rinse with water for several minutes. Remove contact lenses, if present and easy to do. Continue rinsing.
- P308+P316 IF exposed or concerned: Get emergency medical help immediately.
- P316 Get emergency medical help immediately.
- P317 Get medical help.
- 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.
- P332+P317 If skin irritation occurs: Get medical help.
- P361+P364 Take off immediately all contaminated clothing. And wash it before reuse.
- P362+P364 Take off contaminated clothing. And wash it before reuse.
- P390 Absorb spillage to prevent material damage.
- P391 Collect spillage.
- P403+P233 Store in a well-ventilated place. Keep container tightly closed.
- P405 Store locked up.
- P406 Store in corrosive resistant container with a resistant inner liner.
- P501 Dispose of contents and container in accordance with local, regional, national and international regulations.
Substance as classified, dilutions may differ.
Questions
The stock record and the bottle do not agree. What should we do?
Tell your safety lead and senior manager promptly, because an unexplained difference with a substance this toxic needs looking into. Do not open the bottle to weigh it. Note what the label shows and how full it looks, and use that when you arrange the collection.
Can it share a locked cupboard with our sodium cyanide?
Yes, the two share the same hazards and can sit together, provided the cupboard is dry and free of acids and oxidisers. Each still needs its own stock record entry. When you clear them, list both by name, because they should not be merged on paper.
Is caked potassium cyanide more dangerous than a free flowing solid?
It remains rapidly fatal either way, and caking does not make it any less so. It does mean moisture has reached it, which can start hydrogen cyanide forming inside the container. Treat that as a warning, leave the bottle closed and call for specialist help.