Cobalt(II) chloride (CAS 7646-79-9): storage and disposal
Many school and college stores still hold cobalt(II) chloride in two forms: red-pink hexahydrate crystals and strips of blue test paper for detecting water. It is classified for carcinogenicity by inhalation, as a sensitiser, for reproductive harm and as very toxic to aquatic life. Old indicator silica gel can carry it too, which is how it often turns up unlabelled in a drawer.
- CAS number
- 7646-79-9
- Form
- Solid
- Storage class
- Toxic
- Signal word
- Danger
- Usual EWC code
- 16 05 06*
Corrosive
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
Check the drawer before the shelf. Cobalt chloride paper is usually kept in a tube or packet in a technician's desk, with litmus and universal indicator, and that is the wrong home for a carcinogen and sensitiser. Move paper, crystals and any old indicator silica gel into a locked toxic-stock cupboard with a stock record. Keep the material in a locked toxic-stock cupboard and separate it from substances identified as incompatible in the safety data sheet. A tray beneath the jar catches any powder that falls from the cap. Date every container, and make sure the label says hexahydrate where that is what it is.
How to tell it has deteriorated
Colour is how this substance reports on itself. The crystals are red-pink when hydrated and go blue as they lose water, so a jar that has patches of blue or a paper that has turned pink in its tube tells you about humidity in the store. Test paper that has already turned pink has absorbed water and is no longer useful, and paper that has become brittle or stained should be recorded. Lumps, damp crystals, staining around the cap and faded labels point to long storage. Indicator silica gel that has changed colour and lost its label is the one most likely to be forgotten.
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.
Grouping matters because the stock is a mix of forms. Pack the crystals, the used and unused paper and any indicator silica gel as separate items, each sealed and labelled as cobalt chloride, since the collector needs to see what each contains. A laboratory pack uses 16 05 06*, and discarded inorganic stock outside a pack uses 16 05 07*. UN 3288 applies to the carriage. Never put any of it in a bin or sink, and nobody should shake out or wash old silica gel to reuse it. Because powder inhalation is a concern, keep lids taped and request a specialist collection.
| 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 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: hexahydrate, test paper.
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.
- H317 May cause an allergic skin reaction.
- H318 Causes serious eye damage.
- H334 May cause allergy or asthma symptoms or breathing difficulties if inhaled.
- H341 Suspected of causing genetic defects.
- H350i May cause cancer by inhalation.
- H360F May damage fertility.
- H410 Very toxic to aquatic life with long lasting effects.
Precautionary statements
- P203 Obtain, read and follow all safety instructions before use.
- P233 Keep container tightly closed.
- P260 Do not breathe dust, fume, gas, mist, vapours or spray.
- P261 Avoid breathing 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.
- P272 Contaminated work clothing should not be allowed out of the workplace.
- 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+P317 IF SWALLOWED: Get medical help.
- P302+P352 IF ON SKIN: Wash with plenty of water.
- P304+P340 IF INHALED: Remove person to fresh air and keep comfortable for breathing.
- P318 If exposed or concerned, get medical advice.
- P321 Specific treatment (see supplemental first aid instruction on this label).
- P330 Rinse mouth.
- P333+P317 If skin irritation or rash occurs: Get medical help.
- P342+P316 If experiencing respiratory symptoms: Get emergency medical help immediately.
- P362+P364 Take off contaminated clothing. And wash it before reuse.
- P391 Collect spillage.
- P403 Store in a well-ventilated place.
- P405 Store locked up.
- P501 Dispose of contents and container in accordance with local, regional, national and international regulations.
- P264+P265 Wash hands and exposed skin thoroughly after handling. Do not touch eyes.
- P305+P354+P338 IF IN EYES: Immediately rinse with water for several minutes. Remove contact lenses, if present and easy to do. Continue rinsing.
- P317 Get medical help.
Substance as classified, dilutions may differ.
Questions
Is blue cobalt chloride test paper hazardous waste?
Yes. The paper carries cobalt(II) chloride, which is classified for carcinogenicity by inhalation, as a sensitiser, for reproductive harm and as very toxic to aquatic life. Seal it in a labelled container and collect it with the crystals.
Why has the colour changed from blue to pink?
The salt turns pink as it takes up water, so a pink paper or silica gel has absorbed moisture. It is still waste for collection and should not be dried out for reuse.
What is indicator silica gel and why does it matter?
Older indicator silica gel was coloured with cobalt chloride, so a jar of blue or pink gel with no label is a cobalt waste. Keep it closed and describe it in the enquiry.
Where should it be kept?
In a locked toxic-stock cupboard with a stock record, apart from acids and oxidisers. A technician's desk drawer or a shared prep bench is not a suitable place, whichever form the stock takes.
