Iodine (CAS 7553-56-2): storage and disposal
Iodine crystals are held in school and university prep rooms, and in pathology and histology stores where iodine is part of staining work. The crystals are classified as harmful by several routes, irritating to skin, eyes and airways, and very toxic to aquatic life. Because they give off vapour even at room temperature, the condition of the shelf matters as much as the bottle.
- CAS number
- 7553-56-2
- Form
- Solid
- Storage class
- Toxic
- Signal word
- Warning
- Usual EWC code
- 16 05 06*
Harmful or irritant
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
A small iodine bottle can easily end up on a prep room shelf beside metal powders. That is a mistake, because it forms sensitive or violently reacting products with ammonia and reactive metals. Keep it away from aluminium powder, magnesium ribbon, zinc powder, ammonia solution, ammonia gas and acetylene. As toxic stock it belongs in a locked cabinet with a stock record, apart from acids and oxidising stock. Vapour leaves the bottle slowly and stains and corrodes metal, so keep it off metal shelving and away from metal fittings, and make sure the cap is tight.
How to tell it has deteriorated
Start at the cap. A brown stain or crust on the cap, rust on a metal lid, brown marks on the shelf beneath and a purple tint in the air space of the bottle all show that vapour has been escaping. Crystals outside the bottle, on the shoulder or in the cabinet, mean the seal has failed. Iodine sublimes at room temperature, so a bottle that looks half empty may have lost stock through the cap rather than through use. A faded label or a lost stock record adds to the problem. Report any of these signs before the bottle is moved.
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.
Unwanted crystals must never be poured away or rinsed into a sink or drain, because it is very toxic to aquatic life, and nobody should try to decolourise, dissolve or neutralise crystals to get rid of them. Specialist collection is the only route. School and university stock is normally entered as 16 05 06*, while iodine from a human healthcare setting takes 18 01 06*, and UN 3495 applies. Record whether crystals are loose outside the bottle and whether the cap is corroded, so the collector knows what to expect. It travels in a compatible group away from ammonia, reactive metals and acetylene.
| 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.
- AcetyleneIodine forms sensitive or violently reacting products with ammonia and reactive metals.
- Aluminium powderIodine forms sensitive or violently reacting products with ammonia and reactive metals.
- Ammonia gasIodine forms sensitive or violently reacting products with ammonia and reactive metals.
- Ammonia solutionIodine forms sensitive or violently reacting products with ammonia and reactive metals.
- 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.
Show 6 more
- Magnesium ribbonIodine forms sensitive or violently reacting products with ammonia and reactive metals.
- 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.
- Zinc powderIodine forms sensitive or violently reacting products with ammonia and reactive metals.
Common quantities we collect
Usually held as: crystals.
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.
- H312 Harmful in contact with skin.
- H315 Causes skin irritation.
- H319 Causes serious eye irritation.
- H332 Harmful if inhaled.
- H335 May cause respiratory irritation.
- H400 Very toxic to aquatic life.
Precautionary statements
- P261 Avoid breathing dust, fume, gas, mist, vapours or spray.
- 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.
- P302+P352 IF ON SKIN: Wash with plenty of water.
- P304+P340 IF INHALED: Remove person to fresh air and keep comfortable for breathing.
- P317 Get medical help.
- P321 Specific treatment (see supplemental first aid instruction on this label).
- P362+P364 Take off contaminated clothing. And wash it before reuse.
- P391 Collect spillage.
- P501 Dispose of contents and container in accordance with local, regional, national and international regulations.
- P260 Do not breathe dust, fume, gas, mist, vapours or spray.
- 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.
- P301+P317 IF SWALLOWED: Get medical help.
- P305+P351+P338 IF IN EYES: Rinse cautiously with water for several minutes. Remove contact lenses, if present and easy to do. Continue rinsing.
- P319 Get medical help if you feel unwell.
- P330 Rinse mouth.
- P332+P317 If skin irritation occurs: Get medical help.
- P337+P317 If eye irritation persists: Get medical help.
- P403+P233 Store in a well-ventilated place. Keep container tightly closed.
- P405 Store locked up.
Substance as classified, dilutions may differ.
Questions
Why does the shelf under our iodine bottle have brown stains?
Iodine sublimes at room temperature, and the purple vapour stains and corrodes metal caps and nearby shelves. Brown marks mean the bottle has been leaking vapour through its cap. Record the staining without opening or disturbing the bottle, and arrange specialist assessment if the seal appears compromised. Iodine vapour can escape through an inadequate closure and stain nearby surfaces.
Can iodine be stored with other metal powders?
No. Iodine forms sensitive or violently reacting products with ammonia and reactive metals, so aluminium powder, magnesium ribbon and zinc powder must be kept well clear of it, in a different cabinet and not merely on a different shelf.
What should we do about iodine crystals found outside the bottle?
Leave the bottle where it is and raise a collection enquiry describing what you see. Crystals outside the bottle mean the seal has failed and vapour is escaping, which stains and corrodes nearby metal. Do not sweep up or wash away the crystals.
