Phosphotungstic acid (CAS 12501-23-4): storage and disposal
Phosphotungstic acid is held as a pale crystalline hydrate in university labs and histology departments, where it is used in staining and for preparing microscope samples. It is harmful if swallowed, causes severe skin burns and eye damage and is toxic to aquatic life with long lasting effects. A bottle is small and used rarely, so the colour of the solid and the state of the cap tell a holder most about it.
- CAS number
- 12501-23-4
- Form
- Solid
- Storage class
- Acid
- Signal word
- Danger
- Usual EWC code
- 16 05 06*
Corrosive
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 acid 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
Small glass or plastic jars of the hydrate are the usual form, and they belong low down on an acid-resistant tray in a ventilated corrosive store, with the lid firmly on. Keep the jar away from alkalis, oxidisers and toxic salts. It should also be kept clear of paper, cardboard and organic dust, because contact with organic material can turn the solid a blue or green colour. In a histology store, jars of staining reagents are often packed close together, so a labelled spot on the tray is better than a crowded shelf. Date it on arrival.
How to tell it has deteriorated
A pale, free-flowing solid is normal. A blue or green tint is the textbook change, and it appears where the acid meets organic material or has been reduced over time, so a tinted solid usually points to contamination from a spatula, a paper label or dust. Beyond colour, look for caking, which suggests damp, a perished or brittle cap, crust around the neck, a cracked jar and a faded label. A jar with a blue tint, a damaged cap or an unreadable label should stay closed on its tray and be listed for collection, and the colour must not be treated as something to clear.
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 acid laboratory pack with compatible chemicals.
Waste code 16 05 06* applies in a lab pack, 16 05 07* for a discarded inorganic chemical outside one, and 18 01 06* in a healthcare setting. Because it is toxic to aquatic life with long lasting effects, it must never go into a sink or drain, and it must not go in a bin or skip. It must not be diluted or neutralised first either. Say whether the jar holds pale solid or a tinted one, roughly how much is left and whether the neck is crusted. The collector groups it with other acids and keeps it away from alkalis and oxidisers.
| 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
- FlammableOxidising acids can ignite flammable materials, and acid fumes attack containers and seals.
- AlkaliAcids and alkalis react with strong heat and spattering if they meet.
- OxidiserMany oxidisers release toxic gas or become unstable in contact with acid.
- ToxicToxic stock is stored apart from acids. Several toxic salts release toxic gas in contact with acid.
Named chemicals to keep apart
- AcetoneOxidising acids can ignite flammable materials, and acid fumes attack containers and seals.
- Ammonia solutionAcids and alkalis react with strong heat and spattering if they meet.
- Calcium hypochloriteMany oxidisers release toxic gas or become unstable in contact with acid.
- EthanolOxidising acids can ignite flammable materials, and acid fumes attack containers and seals.
- FormalinToxic stock is stored apart from acids. Several toxic salts release toxic gas in contact with acid.
- HexaneOxidising acids can ignite flammable materials, and acid fumes attack containers and seals.
- Hydrogen peroxideMany oxidisers release toxic gas or become unstable in contact with acid.
- Mercury(II) chlorideToxic stock is stored apart from acids. Several toxic salts release toxic gas in contact with acid.
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- MethanolOxidising acids can ignite flammable materials, and acid fumes attack containers and seals.
- Potassium hydroxideAcids and alkalis react with strong heat and spattering if they meet.
- Potassium nitrateMany oxidisers release toxic gas or become unstable in contact with acid.
- Potassium permanganateMany oxidisers release toxic gas or become unstable in contact with acid.
- Sodium cyanideToxic stock is stored apart from acids. Several toxic salts release toxic gas in contact with acid.
- Sodium hydroxideAcids and alkalis react with strong heat and spattering if they meet.
- TolueneOxidising acids can ignite flammable materials, and acid fumes attack containers and seals.
Common quantities we collect
Usually held as: hydrate.
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.
- H411 Toxic to aquatic life with long lasting effects.
Precautionary statements
- 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.
- P273 Avoid release to the environment.
- 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.
- P317 Get medical help.
- P321 Specific treatment (see supplemental first aid instruction on this label).
- P330 Rinse mouth.
- P363 Wash contaminated clothing before reuse.
- P391 Collect spillage.
- 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 phosphotungstic acid gone blue or green?
Contact with organic material, such as dust, paper or a dirty spatula, or slow reduction over time, can tint the solid blue or green. The jar is still a corrosive acid. Keep it closed, do not try to clear the colour, and list it for collection.
Where should the hydrate be stored in a histology department?
Low down on an acid-resistant tray in a ventilated corrosive store, away from alkalis, oxidisers and paper. Label the spot and date the jar on arrival, rather than leaving it among crowded staining reagents.
Is a small leftover amount treated differently because it is a stain?
No. It is toxic to aquatic life with long lasting effects and causes severe burns, so it must never go into a sink or drain. Even a small leftover is chemical waste for specialist collection.
