Cacodylic acid (CAS 75-60-5): storage and disposal
Arsenic sits in the formula of cacodylic acid, and that is why this solid is kept in a locked cabinet in university and histology stores, often left over from electron microscopy work. It is classified as toxic if swallowed or inhaled and very toxic to aquatic life. Old, half-used jars are the usual problem, since few staff still use it and records tend to lapse.
- CAS number
- 75-60-5
- Form
- Solid
- Storage class
- Toxic
- Signal word
- Danger
- Usual EWC code
- 16 05 06*
Acute toxicity
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
Keep it apart from oxidisers and from acids. Keep cacodylic acid apart from incompatible materials named on the product safety data sheet. Cacodylic acid goes in a locked cabinet with a stock record, well away from food and drink areas. Histology and university labs often keep the jar in the same cabinet as fixatives and stains, so check that nothing acidic or oxidising shares the shelf. The record should show who last used it and how much remains. A sealed secondary container under the jar helps catch any leak.
How to tell it has deteriorated
Few visible signs appear on this substance, so the container and the paperwork are what tell you about its age. Faded labels, staining round the cap, a seal that no longer closes and a stock record that has gone missing are the practical checks. An unexpected colour change or caking in the solid is also worth noting. Because the contents are classified as toxic if inhaled, nobody should open an old jar to look inside. Look through the container or at the outside only, and treat a jar with no readable label as unknown stock until the collector identifies it.
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.
Record the quantity left, the jar condition and the date of the last entry in the stock book, since the carrier needs an accurate description of an arsenic compound. The common code for a laboratory chemical applies, with the organic chemical variant sometimes used for discarded stock outside a lab pack and a healthcare variant for hospital holders. Leave the jar in its locked cabinet until collection. It must not be tipped away, rinsed down a sink or put in general waste. Attempts to deactivate it are never appropriate. The specialist carrier packs it separately from acids and oxidisers.
| EWC code, laboratory chemicals | 16 05 06* |
|---|---|
| Discarded organic chemical, not a laboratory pack | 16 05 08* |
| 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.
- 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: solid.
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
- H301 Toxic if swallowed.
- H331 Toxic if inhaled.
- H410 Very toxic to aquatic life with long lasting effects.
Precautionary statements
- 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.
- P273 Avoid release to the environment.
- P301+P316 IF SWALLOWED: Get emergency medical help immediately.
- P304+P340 IF INHALED: Remove person to fresh air and keep comfortable for breathing.
- P316 Get emergency medical help immediately.
- P321 Specific treatment (see supplemental first aid instruction on this label).
- P330 Rinse mouth.
- P391 Collect spillage.
- 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 does a cacodylic acid jar need special handling at disposal?
It contains arsenic and is classified as toxic if swallowed or inhaled and very toxic to aquatic life. That makes it hazardous waste that only a specialist collection can take, packed away from acids and oxidisers.
Can we keep it with other histology fixatives?
Only if the cabinet is locked and nothing acidic or oxidising is on the same shelf. Keep a separate stock record and a clear label showing it contains arsenic.
What should we do with a jar nobody has used for years?
Leave it sealed in the locked cabinet, check the label and the stock record, and request collection. Do not open the jar to inspect the contents, because the solid is classified as toxic if inhaled and an old seal may have failed.
