Crystal violet (CAS 548-62-9): storage and disposal
Better known as gentian violet, crystal violet is a staining dye that has sat in Gram stain sets in school, college, pathology and veterinary labs for generations. It is classified as harmful if swallowed, as causing serious eye damage, as something that may cause cancer and as very toxic to aquatic life. Because the same label can cover different grades, the stricter carcinogen entry is the one shown here, and that sets the standard for how old bottles are handled.
- CAS number
- 548-62-9
- Form
- Solid
- Storage class
- Toxic
- Signal word
- Danger
- Usual EWC code
- 16 05 06*
Corrosive
Harmful or irritant
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
A locked cabinet with a stock record is where this dye belongs well away from food and drink areas. Keep it apart from oxidisers and segregate acid stock to avoid incompatible contact. Its carcinogenic and eye damage classifications also support controlled storage and careful containment. Gram stain kits are the usual way it reaches a school or college, so the small dropper bottle in the kit box is often the real item to account for. Powder bottles go in a tray, not loose on a shelf. Because the dye marks skin, labels and worktops, stand each bottle on something that shows a leak straight away, and write a date of receipt on it.
How to tell it has deteriorated
Fresh powder is dark with a metallic green look at the crystal faces, and its solutions are an unmistakable violet. A purple ring around a cap, violet stains on the label or on the shelf below show that a seal has failed, and a stained label that can no longer be read turns a bottle into an unknown. Check for loose crystal dust on the shoulder of the bottle, a crust in the thread and a stock record that no longer matches the container. Few other visible changes tell you a bottle is old, so a lost record, an unreadable label and a cracked or sticky container are the markers to act on. Do not open an unlabelled violet bottle to find out more.
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.
Open the request with the waste code that fits the holder, usually 16 05 06* for a prep room or research store, 18 01 06* for human healthcare and 18 02 05* for a veterinary practice. Because the carcinogen classification is the reason this dye is handled with such care, say exactly what is in each container: powder, a Gram stain bottle or a working solution, and its size. Keep Gram sets complete in their boxes where the bottles are intact. Rinsing stain into a sink is not allowed, and a spill on the bench is cleaned only by someone competent, with the cleaning materials bagged and listed with the stock.
| EWC code, laboratory chemicals | 16 05 06* |
|---|---|
| Discarded organic chemical, not a laboratory pack | 16 05 08* |
| Human healthcare setting | 18 01 06* |
| Veterinary setting | 18 02 05* |
| 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, Gram stain.
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.
- H318 Causes serious eye damage.
- H350 May cause cancer.
- H410 Very toxic to aquatic life with long lasting effects.
Substance as classified, dilutions may differ.
Questions
Why is crystal violet treated as a carcinogen if a bottle looks like any other dye?
The GB list has two entries depending on the grade, and a bottle does not show which one it is. The stricter entry, a known carcinogen hazard, is therefore the sensible basis for handling and describing it.
Is a Gram stain kit collected whole or bottle by bottle?
List each bottle in the kit, because the crystal violet, the other stains and any solvent are described separately. Intact kits can stay boxed so the contents are easy to check, and any leaking bottle is flagged on the request.
Can we keep an old bottle of gentian violet for teaching demonstrations?
Only while it is dated, labelled and in a good container with a stock record. It gives few signs of age, so a bottle without a date or with a stained label is better listed for collection than kept for occasional use.
Does crystal violet go in the same lab pack as acids?
No. Keep crystal violet segregated from incompatible chemicals, including oxidisers. Acid-containing mixtures should be assessed for compatibility before packing, rather than placing them together simply because they are laboratory chemicals. The collector packs it in a compatible group with other dyes and stains.
