Merbromin (CAS 129-16-8): storage and disposal
Merbromin is a legacy mercury containing antiseptic, seen in pharmacy cupboards either as a dark solid or as a deep red solution. As classified the substance is fatal if swallowed, in contact with skin or if inhaled, and very toxic to aquatic life, while an old dilute antiseptic may be less hazardous than that but is still not safe. It stays a mercury waste whatever the strength, which decides how it is handled.
- CAS number
- 129-16-8
- Form
- Solid
- Storage class
- Toxic
- Signal word
- Danger
- Usual EWC code
- 16 05 06*
Acute toxicity
Serious health hazard
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
In a pharmacy it tends to surface at the back of a cupboard or in forgotten first aid stock, usually as a small bottle with an old style label that says nothing about mercury. Once found, it should move out of the general medicines shelf and into a locked cabinet with a stock record, away from acids, oxidisers and anything taken by patients. The dye marks whatever it touches, so a tray beneath the bottle protects shelving and shows up a leak quickly. Put a plain added label on it stating that it contains mercury and is not for issue. That single step stops the commonest error with this stock, which is an old antiseptic being treated as a routine expired medicine.
How to tell it has deteriorated
A red stain is what a technician will see first. Merbromin is a strong dye, so seepage from a tired cap marks the bottle neck, label and shelf a deep red that outlasts any liquid. The solid is dark, often with a green sheen, and that is normal for it. Beyond those colours it gives few visible signs of age. A solution may have dried down to a dark crust, leaving no clear idea of its strength. A faded label, a perished cap or a missing stock record are the other common faults. Staining shows the seal has failed, and it does not tell you the contents have become less of a mercury concern.
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.
Before asking for a collection, note what the label actually says, the bottle size, how full it is and whether it is solid, liquid or dried down. Any old brand wording should be copied exactly, since it may be the only clue to the mercury. It stays a mercury waste whatever the strength, and in a hospital or community pharmacy the usual code is 18 01 06*. Give the number of bottles if several turn up together. Expect it to be grouped with toxic stock, away from ordinary medicines. Its only route is specialist collection. Never send it down a sink or drain or put it in a general waste bin or skip, and do not try to treat it first.
| 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: legacy antiseptic.
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
- H300 Fatal if swallowed.
- H310 Fatal in contact with skin.
- H330 Fatal if inhaled.
- H373 May cause damage to organs through prolonged or repeated exposure.
- H410 Very toxic to aquatic life with long lasting effects.
Substance as classified, dilutions may differ.
Questions
Can old merbromin antiseptic go out with our expired medicines?
No, because it stays a mercury waste and should be described as one. Take it out of the routine returns, label it as containing mercury, lock it away and arrange a specialist collection, giving the bottle count and how full each one is.
There is red staining on the shelf under the bottle. What should we do?
Leave the bottle closed and stop using that shelf for other stock. Do not scrub the mark or try to clean it with any product. Note the staining, because it shows the seal has failed, and tell whoever arranges the collection so the packing can allow for it.
The solution has dried to a dark crust. Is it still a problem?
Yes. Drying removes the liquid but leaves the mercury, and it is no longer clear what strength remains. Keep the bottle upright and closed in the locked cabinet, describe it as dried residue, and ask for a specialist collection in the usual way.