Sodium cacodylate (CAS 124-65-2): storage and disposal
Histology and university labs hold sodium cacodylate mainly as buffer stock, usually the trihydrate, left over from fixative work. The arsenic in its formula and the classification as toxic if swallowed, toxic if inhaled and very toxic to aquatic life shape every decision about it. Old buffer bottles with fading labels are the common problem, because the arsenic content is easy to forget.
- CAS number
- 124-65-2
- 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
As a toxic salt, this buffer stock goes in a locked cabinet with a stock record, away from food and drink areas. Keep sodium cacodylate apart from acids, which convert it to cacodylic acid, and from oxidising agents, following the product safety data sheet. Histology labs often keep dry stock and made-up buffer in neighbouring places, and both need the same care: label each bottle to say it contains arsenic. A tray under the bottles catches leaks. Date the stock on arrival and write any later entries in the record, so the quantity remaining can be given accurately when collection is arranged.
How to tell it has deteriorated
A salt that has taken in moisture over time may look damp or clump in the container, and this is the first thing worth checking on an old jar of the trihydrate. Beyond that, few distinctive signs mark this substance. Look at the label, the cap, the neck and the cabinet shelf. Faded writing, staining round the cap, a failed seal or a missing stock record each count as a reason to arrange collection. A bottle of made-up buffer with no date, or one with cloudiness or growth, should be treated as unknown and left unopened and untouched.
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.
Start with the waste code, because it tells the carrier what kind of chemical this is. For a laboratory with a lab pack the standard laboratory chemical code applies, and an inorganic or organic discarded-chemical variant is used where the item is collected outside a lab pack. Hospital holders use the healthcare code. Give the quantity, the form (dry stock or made-up buffer) and the container condition. It must not be poured away, put into general waste or treated to make it milder, and it stays in the locked cabinet until collection.
| 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: buffer stock, trihydrate.
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
Does a dilute cacodylate buffer still need specialist collection?
Yes. A dilute buffer may be less hazardous than the dry salt, but it still contains arsenic and is collected as chemical waste. It must never go to a sink or drain, and it stays labelled until collection.
Should dry salt and made-up buffer be stored together?
They can share a locked cabinet if each bottle is clearly labelled and the shelf is free of acids and oxidisers. Keep the stock record up to date for both.
What do we record about an old bottle?
Note the form, the approximate volume, the label wording and any damage to the cap or container. If the label is unreadable, say so and the carrier will describe it accurately.
