Chloroform: safe storage and disposal
Chloroform (CAS 67-66-3) is a dense, sweet-smelling chlorinated solvent. It is still in routine use in molecular biology and analytical work, and it survives as a forgotten bottle in many school and hospital stores, sometimes dating from its days as an anaesthetic. Its GHS signal word is Danger. The hazard statements are H302 Harmful if swallowed, H315 Causes skin irritation, H319 Causes serious eye irritation, H331 Toxic if inhaled, H351 Suspected of causing cancer, H361d Suspected of damaging the unborn child and H372 Causes damage to organs through prolonged or repeated exposure.
- CAS number
- 67-66-3
- Form
- Liquid
- Storage class
- Toxic
- Signal word
- Danger
- Usual EWC code
- 16 05 06*
Acute toxicity
Serious health hazard
What to do this week
- Leave it where it is. If it looks old, crystalline or damaged, do not open or move it and keep people away from the shelf.
- Write down the label wording, the rough age and where it is stored, from a safe distance.
- Send us those details, and a photo if you can take one without touching it.
Safe storage of chloroform in a school or lab
Chloroform sits with toxic stock. It is not flammable in the usual sense, so it does not belong in the flammables cabinet by default, and it should be kept away from reactive metals and strong alkalis. Keep it locked away, in its original amber or dark bottle, and away from light and heat. A low shelf inside a tray is a sensible position, as a broken bottle gives off toxic vapour quickly.
Date the bottle on arrival and when first opened. Chloroform is normally supplied with a small amount of stabiliser, and the label or data sheet will say which. Your COSHH assessment sets out how it should be handled, which usually means working in a fume cupboard.
How to tell chloroform has deteriorated
Chloroform becomes unstable with age for one reason. Without an effective stabiliser, light and air slowly turn it into phosgene, a highly toxic gas, as well as hydrochloric acid. The stabiliser is used up over time, and a part-empty bottle with a lot of air above the liquid is the most concerning case.
You cannot judge this safely by opening a bottle, and you should never smell it. From the outside, look for an undated or very old label, a clear glass bottle that has stood in the light, a corroded cap, fume damage or staining around the neck and any discolouration of the contents. Older anaesthetic-grade bottles should be treated as suspect.
If you find any of this, leave the bottle closed and where it is, keep people away from the area and get a specialist assessment. Do not test the contents and do not add anything. If you notice irritating vapour, leave the room, close the door, keep others out and call 999 if there is danger.
Without its stabiliser, light and air slowly convert it to phosgene.
How chloroform must be disposed of
Sound chloroform in date goes by specialist collection. Old or suspect stock goes through an assessment first. Do not put it down any sink, and do not leave it to evaporate. Evaporating chloroform in a fume cupboard moves a suspected carcinogen into the air and creates no record of what happened to it.
| Setting | Usual List of Wastes code | Hazardous |
|---|---|---|
| Laboratory chemical, including school and university | 16 05 06* | Yes |
| Discarded organic chemical, not in a laboratory pack | 16 05 08* | Yes |
| Human healthcare setting | 18 01 06* | Yes |
For transport, chloroform is UN 1888, packing group III. Unless a permit allows it, it is illegal to mix hazardous waste with other waste, so a chlorinated stream stays on its own. Regular volumes from research work are usually handled through solvent waste collection, with chlorinated and non-chlorinated waste as separate lines.
| EWC code, laboratory chemicals | 16 05 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 chloroform with
- Acetone and strong alkalis, such as sodium hydroxide and potassium hydroxide. Chloroform can react violently with strong alkalis, especially when acetone is present. A shared waste bottle is the usual setting for this accident.
- Sodium metal, potassium and lithium. Chlorinated solvents and reactive metals are a well-known dangerous pairing.
- Sodium azide, which should stay away from chlorinated solvents.
- Oxidisers and acids as storage classes.
- 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.
- AcetoneChloroform can react violently with strong alkalis, especially when acetone is present.
- 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.
- Lithium metalAlkali metals can react explosively with chlorinated solvents.
- Nitric acidToxic stock is stored apart from acids. Several toxic salts release toxic gas in contact with acid.
- Potassium hydroxideChloroform can react violently with strong alkalis, especially when acetone is present.
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- Potassium metalAlkali metals can react explosively with chlorinated solvents.
- 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.
- Sodium azideAzides can form explosive azidoalkanes with halogenated solvents.
- Sodium hydroxideChloroform can react violently with strong alkalis, especially when acetone is present.
- Sodium metalAlkali metals can react explosively with chlorinated solvents.
- Sulfuric acidToxic stock is stored apart from acids. Several toxic salts release toxic gas in contact with acid.
Common quantities of chloroform collected
Research labs usually hold Winchesters and small working bottles, along with waste containers from extraction protocols. Schools usually hold a single old bottle or nothing at all. Hospital and pathology stores may contain very old bottles, sometimes of anaesthetic grade, found during a move or closure.
Usually held as: neat, legacy anaesthetic.
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.
Chloroform in different sectors
Schools and colleges. Chloroform is unusual in current school practice. An old bottle is more likely to be a legacy find, and it should be treated as a suspect item and raised with your advisory service, CLEAPSS or SSERC, as well as a specialist.
Universities and research. Phenol-chloroform extractions make small but steady waste. Keep waste bottles closed, labelled and away from acetone wash bottles. Other chlorinated solvents, such as dichloromethane, are often used nearby. Keep the description of each mixed stream accurate.
Hospitals and pathology. The chemical code 18 01 06* usually applies, and waste chemicals stay out of clinical and offensive waste.
Dental practices. Chloroform was used historically for some root canal procedures. Older bottles in a surgery cupboard should be left closed and passed to a specialist if they are old or undated.
Hazard data from PubChem GHS classification, retrieved 31 October 2026. Guidance only. Check your own risk assessment and your supplier's safety data sheet.
Hazard statements
- H302 Harmful if swallowed.
- H315 Causes skin irritation.
- H319 Causes serious eye irritation.
- H331 Toxic if inhaled.
- H351 Suspected of causing cancer.
- H361d Suspected of damaging the unborn child.
- H372 Causes damage to organs through prolonged or repeated exposure.
Precautionary statements
- P203 Obtain, read and follow all safety instructions before use.
- P260 Do not breathe dust, fume, gas, mist, vapours or spray.
- P261 Avoid breathing 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.
- P271 Use only outdoors or in a well-ventilated area.
- P280 Wear protective gloves, protective clothing, eye protection and face protection.
- P301+P317 IF SWALLOWED: Get medical help.
- P302+P352 IF ON SKIN: Wash with plenty of water.
- P304+P340 IF INHALED: Remove person to fresh air and keep comfortable for breathing.
- P305+P351+P338 IF IN EYES: Rinse cautiously with water for several minutes. Remove contact lenses, if present and easy to do. Continue rinsing.
- P316 Get emergency medical help immediately.
- P318 If exposed or concerned, get medical advice.
- P319 Get medical help if you feel unwell.
- P321 Specific treatment (see supplemental first aid instruction on this label).
- P330 Rinse mouth.
- P332+P317 If skin irritation occurs: Get medical help.
- P337+P317 If eye irritation persists: Get medical help.
- P362+P364 Take off contaminated clothing. And wash it before reuse.
- 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
We have an old bottle of chloroform with no stabiliser listed. What should we do?
Leave it closed and where it stands. Without a working stabiliser, light and air slowly form highly toxic phosgene, and you cannot judge that by looking. Record what the label shows, keep people away from that shelf, and ask for a specialist assessment before collection.
Can chloroform and acetone wastes from the histology bench go in one bottle?
No. Chloroform can react violently with strong alkalis, particularly when acetone is present, and a mixed waste bottle can pick up traces of anything. Keep separate labelled containers, and tell the collection team exactly what each holds. An existing mixed bottle should be left closed and described.
Does a small dental bottle of chloroform need the same care as a large one?
Yes. A small bottle presents the same chemical incompatibilities and potential degradation hazards as a larger one. Sound stock requires protection from light and separation from alkalis and acetone. If the bottle is old, undated or its stabiliser status is uncertain, leave it closed and undisturbed and arrange specialist assessment before collection. The small volume does not remove these precautions.
