Potassium carbonate (CAS 584-08-7): storage and disposal
School, college and university stores hold potassium carbonate as a white solid, used in teaching and as a drying agent. It is classified Warning for skin irritation, serious eye irritation and respiratory irritation, and it belongs with the alkalis. Its defining habit is that it draws water from the air so strongly that a tub left loose turns wet, which changes it from a stored powder into a sticky problem.
- CAS number
- 584-08-7
- Form
- Solid
- Storage class
- Alkali
- Signal word
- Warning
- Usual EWC code, laboratory stock
- 16 05 06*
Harmful or irritant
What to do this week
- Without moving anything that looks damaged, check the label is readable and write down the opened date if it is not already there.
- Check it is stored as alkali stock, and apart from anything listed under "Do not store with" on this page. If nothing is listed, that does not prove it is safe with everything.
- If you no longer need it, add it to your disposal list so it can be included in a collection.
Safe storage in a school or lab
Check the tub externally for dampness, crusting, a poor seal or signs of leakage. Do not tilt or open a suspect container to determine whether the contents have caked. Because potassium carbonate draws water from the air, keep the cap tight, and if the tub sits in a humid prep room, check it more often. Keep it low in the alkali store on a tray, away from acids, which react with strong heat and spattering if they meet. Open the tub carefully, since the dust irritates the airways as well as the skin and eyes.
How to tell it has deteriorated
Dry, white powder that scoops easily is normal. The first sign of trouble is damp: potassium carbonate is so keen on moisture that it clumps, then becomes a wet, sticky mass that may leak a clear alkaline liquid through a poor seal. That liquid stains labels and attacks the cap. A crust around the neck and a cap stuck to the tub point to the same cause. Labels often curl and fade where liquid has crept. A tub like this should not be opened to look at. Record it, keep it upright and tell the collector.
How it is disposed of
We arrange this by specialist collection. We do not publish a drain or general waste route for any chemical. It is normally packed in a corrosive alkali laboratory pack with compatible chemicals.
Describe the tub as it is: loose powder, a caked block or a wet mass, and its size. A wet stock is awkward to collect because it can leak through the lid, so say so when you book. Potassium carbonate is usually a hazardous entry, 16 05 06*, because of its classification, though the producer classifies the waste, and the paperwork reflects that. It must not go into a sink, a drain, a general waste bin or a skip, and nobody should add acid or water to deal with a damp tub. Specialist collection packs it with other alkalis, apart from acids.
| Usual EWC code, laboratory stock | 16 05 06* |
|---|---|
| Discarded inorganic chemical, not a laboratory pack | 16 05 07* |
| Usually classed as hazardous waste | Yes |
The code depends on where the waste came from and what it contains, and classifying it is the producer's duty. Use the waste code finder to see why.
Do not store with
- AcidAcids and alkalis react with strong heat and spattering if they meet.
- OxidiserSome oxidisers react strongly with alkalis, and ammonia based stock is especially at risk.
Named chemicals to keep apart
- Acetic acidAcids and alkalis react with strong heat and spattering if they meet.
- Calcium hypochloriteSome oxidisers react strongly with alkalis, and ammonia based stock is especially at risk.
- Hydrochloric acidAcids and alkalis react with strong heat and spattering if they meet.
- Hydrogen peroxideSome oxidisers react strongly with alkalis, and ammonia based stock is especially at risk.
- Nitric acidAcids and alkalis react with strong heat and spattering if they meet.
- Potassium nitrateSome oxidisers react strongly with alkalis, and ammonia based stock is especially at risk.
- Potassium permanganateSome oxidisers react strongly with alkalis, and ammonia based stock is especially at risk.
- Sulfuric acidAcids and alkalis react with strong heat and spattering if they meet.
Common quantities
Usually held as: solid.
Tell us the container size and how many you hold. An estimate is enough to start with, and some items cannot be priced until someone has looked at them.
Where it is commonly held
Hazard statements
- H315 Causes skin irritation.
- H319 Causes serious eye irritation.
- H335 May cause respiratory irritation.
Precautionary statements
- P261 Avoid breathing 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.
- P271 Use only outdoors or in a well-ventilated area.
- P280 Wear protective gloves, protective clothing, eye protection and face 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.
- 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.
- P321 Specific treatment (see supplemental first aid instruction on this label).
- P330 Rinse mouth.
- P332+P317 If skin irritation occurs: Get medical help.
- P337+P317 If eye irritation persists: Get medical help.
- P362+P364 Take off contaminated clothing. And wash it 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.
Substance as classified, dilutions may differ.
Questions
Why has our potassium carbonate turned into a wet lump?
It draws water from the air strongly, so a tub that has not sealed can turn clumpy and then wet. Do not add anything to dry it or break it up. Record the tub, keep it upright on a tray and mention the damp when booking collection.
Is damp potassium carbonate still usable?
Not reliably. Its strength and condition are no longer what the label says, and a wet stock can leak. The classification covers skin, eye and respiratory irritation, so treat caked or wet stock as surplus and arrange collection.
Where does it sit relative to acids?
Lower than them and on its own tray. Acids and alkalis react with strong heat and spattering if they meet, so a leaking acid bottle above an alkali tub is the arrangement to avoid.
