Osmium tetroxide (CAS 20816-12-0): storage and disposal
Osmium tetroxide is a highly volatile strong oxidiser sold in sealed glass ampoules and as 2% and 4% solutions, held in university, pathology and histology settings. It is fatal if swallowed, in contact with skin or if inhaled, causes severe burns and may cause allergy or asthma symptoms. Its vapour can fix the cornea and cause blindness at low levels. Because it passes through ordinary seals, the container decides everything about how it is handled.
- CAS number
- 20816-12-0
- Form
- Solid
- Storage class
- Toxic
- Signal word
- Danger
- Usual EWC code
- 16 05 06*
Corrosive
Acute toxicity
Serious health hazard
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
Sealed glass ampoules are the usual form, or 2% and 4% solutions, and an ordinary screw cap is not enough on its own because the vapour passes through it. Each one belongs inside a sealed secondary container, in a locked and labelled store with a stock record. The label on the store door matters as well, so that nobody opens it unawares. Organic material reacts with it and blackens as it reduces, so the secondary container should be clear of cardboard, foam or ethanol wipes. Acetone, ethanol, glucose and hydrochloric acid must be kept away, since they can react and release toxic gas. In histology that means keeping it away from the processing solvents on the bench, and away from fridges full of samples.
How to tell it has deteriorated
A sound ampoule is intact, with a pale yellow crystalline solid or a clear solution inside and clean glass. What does not belong is black. A black deposit in a secondary container, on a cap, on a tray or on nearby packing shows that the vapour has escaped and met organic material. A cracked ampoule and a sharp chlorine-like smell in the store are the other warning signs, and at that stage you should not go looking for the source. Leave, close the store and keep others out. A leak needs a specialist response, and nobody should try to clean it up or reduce it. Faded labels matter too, as a solution of unknown strength cannot be assumed to be any safer.
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.
For hospital histology and pathology departments, the code is 18 01 06*, the human healthcare entry. University electron microscopy stock uses 16 05 06* in a lab pack, and each carries the asterisk for hazardous waste. Give the count of intact ampoules and bottles of solution, with stated strengths and whether a secondary container is sealed and free of black deposit. That information decides how the items are grouped, since a strong oxidiser cannot be packed near organics, solvents or acids. A dilute solution may be less hazardous than the solid, but it is still not safe. Specialist collection is the only route. Never send it to a sink, drain, general waste bin or skip, and never try to reduce or treat it first.
| EWC code, laboratory chemicals | 16 05 06* |
|---|---|
| Discarded inorganic chemical, not a laboratory pack | 16 05 07* |
| Human healthcare setting | 18 01 06* |
| 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.
- AcetoneOsmium tetroxide is a strong oxidiser that reacts with these materials and can release toxic gas.
- Calcium hypochloriteToxic and oxidising stock are stored apart. A reaction could release toxic vapours.
- EthanolOsmium tetroxide is a strong oxidiser that reacts with these materials and can release toxic gas.
- GlucoseOsmium tetroxide is a strong oxidiser that reacts with these materials and can release toxic gas.
- Hydrochloric acidOsmium tetroxide is a strong oxidiser that reacts with these materials and can release toxic gas.
- 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.
Show 3 more
- 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: sealed ampoules, 2% and 4% solutions.
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.
- H314 Causes severe skin burns and eye damage.
- H330 Fatal if inhaled.
- H334 May cause allergy or asthma symptoms or breathing difficulties if inhaled.
Precautionary statements
- 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.
- P270 Do not eat, drink or smoke when using this product.
- P271 Use only outdoors or in a well-ventilated area.
- 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.
- P301+P330+P331 IF SWALLOWED: Rinse mouth. Do NOT induce vomiting.
- P302+P352 IF ON SKIN: Wash with plenty of water.
- P302+P361+P354 IF ON SKIN: Take off immediately all contaminated clothing. Immediately rinse with water for several minutes.
- 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.
- P316 Get emergency medical help immediately.
- 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.
- P361+P364 Take off immediately all contaminated clothing. And wash it before reuse.
- P363 Wash contaminated clothing before reuse.
- 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.
- P233 Keep container tightly closed.
- P342+P316 If experiencing respiratory symptoms: Get emergency medical help immediately.
- P403 Store in a well-ventilated place.
Substance as classified, dilutions may differ.
Questions
We can smell something sharp near the osmium store. What should we do?
Leave, close the door, keep others out and follow your site emergency procedure. A sharp chlorine-like smell is a warning sign, and the vapour can harm the eyes at low levels. Do not look for the source or try to clean up. A leak needs a specialist response.
There is a black mark inside the secondary container. Does this mean a leak?
It suggests vapour has escaped from the ampoule or bottle, since osmium tetroxide blackens as it reduces on organic material. Do not open the secondary container to check. Keep it closed, keep the store labelled and locked, and ask for specialist advice before any collection.
Can used osmium fixative go with the other histology waste?
No. It should stay in its own sealed and labelled container, never mixed with solvents or other fixatives, and it goes by specialist collection. A used solution may be weaker than the original, but it is not safe, and mixing could release toxic gas.
Is the laboratory fridge a good place to keep an opened ampoule?
Only inside a sealed secondary container, in a labelled unit used for nothing else. The vapour passes through ordinary seals, and a shared fridge exposes samples and everyone who opens the door. An opened ampoule with no current use is better recorded and arranged for collection.
