Potassium hydroxide (CAS 1310-58-3): storage and disposal
Colleges and university laboratories hold potassium hydroxide as pellets, 1 M solution and a 10% solution, and pathology and histology rooms use the solution on the bench. It is classified Danger for severe skin burns and eye damage, and it is harmful if swallowed. The pellets fuse into a hard mass when a tub is left loose, which is what most often turns a tidy stock into an awkward collection.
- CAS number
- 1310-58-3
- Form
- Solid
- Storage class
- Alkali
- Signal word
- Danger
- Usual EWC code
- 16 05 06*
Corrosive
Harmful or irritant
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 alkali 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
Skin and eye burns decide the place: low down, on a resistant tray, in the corrosive store, with the tub cap pressed fully home after every use. Because it is also harmful if swallowed, keep it out of any shared area with food or drink. Ammonium salts are the common mistake: strong alkalis release ammonia gas from them, so ammonium chloride or ammonium sulfate must not share a shelf. Aluminium powder is another partner to separate, and the hydroxide itself attacks aluminium and zinc, so avoid aluminium trays. Acids belong on a different level in their own tray.
How to tell it has deteriorated
A tub that has been opened a few times often holds pellets stuck together into a damp block. The stock takes up moisture and carbon dioxide from the air, so a white crust may form on the pellets and around the thread of the cap. Clear 1 M or 10% solutions give few other visible signs, but a stiff cap or a crust round the stopper shows the closure has been attacked. Metal fittings near the store that look pitted or corroded suggest leakage or splashing. A label dissolved by a drip may leave the strength unreadable, and that bottle must be recorded as unknown.
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 corrosive alkali laboratory pack with compatible chemicals.
The entry for this item is 16 05 06*, and the asterisk marks it as hazardous waste, so a consignment note follows it. It must not go into a sink, a drain, a general waste bin or a skip, and nobody should neutralise a solution or dissolve fused pellets to get them out. Specialist collection packs it with other alkalis, away from acids and ammonium salts. Record the form: pellets, 1 M or 10% solution, the container size and whether the pellets have fused. A block that has set in the tub is described as it is and collected in its tub.
| 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
- 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.
- Aluminium powderStrong alkalis release flammable hydrogen with these metals.
- Ammonium acetateStrong alkalis release ammonia gas from ammonium salts.
- Ammonium carbonateStrong alkalis release ammonia gas from ammonium salts.
- Ammonium chlorideStrong alkalis release ammonia gas from ammonium salts.
- Ammonium nitrateStrong alkalis release ammonia gas from ammonium salts.
- Ammonium oxalateStrong alkalis release ammonia gas from ammonium salts.
- Ammonium sulfateStrong alkalis release ammonia gas from ammonium salts.
Show 11 more
- Ammonium thiocyanateStrong alkalis release ammonia gas from ammonium salts.
- Calcium hypochloriteSome oxidisers react strongly with alkalis, and ammonia based stock is especially at risk.
- ChloroformChloroform can react violently with strong alkalis, especially when acetone is present.
- 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.
- Tin metalStrong alkalis release flammable hydrogen with these metals.
- Zinc powderStrong alkalis release flammable hydrogen with these metals.
Common quantities we collect
Usually held as: pellets, 1 M, 10% solution.
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.
- H314 Causes severe skin burns and eye damage.
Precautionary statements
- P260 Do not breathe 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.
- P280 Wear protective gloves, protective clothing, eye protection and face protection.
- P301+P317 IF SWALLOWED: Get medical help.
- P301+P330+P331 IF SWALLOWED: Rinse mouth. Do NOT induce vomiting.
- 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.
- P321 Specific treatment (see supplemental first aid instruction on this label).
- P330 Rinse mouth.
- P363 Wash contaminated clothing before reuse.
- 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
Can fused potassium hydroxide pellets be broken up for disposal?
No. Breaking up or dissolving a fused block means handling a corrosive solid and risks splashes. Leave the pellets in their original tub, record that they have fused, and tell the collector, who will pack the whole container.
Why must ammonium salts be kept apart?
Strong alkalis release ammonia gas from ammonium salts. If a leaking tub touches ammonium chloride or sulfate on a shared shelf, gas can build up in the cupboard. Store the two on separate shelves or in separate cabinets with trays.
Is 10% potassium hydroxide solution treated the same as pellets?
A solution may be less hazardous than the pellets, but it is not safe to assume so. Solid and solution are described separately for collection, so record the form and strength and check the label before packing.
