Dimethyl sulfate (CAS 77-78-1): storage and disposal
Dimethyl sulfate is a colourless, oily alkylating agent, long used for methylation work, and in UK labs it mostly survives as legacy stock in university stores. It is fatal if inhaled, causes severe burns and may cause cancer, yet it gives little warning smell. That absence of warning, together with the age of the container it usually sits in, decides how it is handled.
- CAS number
- 77-78-1
- Form
- Liquid
- Storage class
- Toxic
- Signal word
- Danger
- Usual EWC code
- 16 05 06*
Corrosive
Acute toxicity
Serious health hazard
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
Inhalation is the hazard that decides where it goes. Under H330 a slow leak can do serious harm before anyone notices a smell, so a locked cabinet with a stock record is the minimum, away from food and drink areas and from acids and oxidisers. A resistant tray beneath the bottle helps because the liquid also burns skin and eyes. Damp matters too, as water slowly breaks the ester down into acidic products that attack closures. The name misleads people. Newcomers read sulfate and assume an ordinary salt, so make sure the label spells out what it is. Give it a named owner when the research group that bought it has moved on.
How to tell it has deteriorated
Start with the cap and label, and look without lifting the bottle. A corroded or brittle cap, a crust at the neck or a stain on the shelf is the useful evidence, because moisture getting in slowly converts the ester into acidic products that attack closures. The liquid itself is colourless and oily, and it gives few visible signs as it ages, so a normal appearance proves little. Smell is no guide at all, and nobody should try to use it as one. A faded label or a lost stock record matters as much as physical damage. An unidentified oily liquid in an old research store should be left alone until someone competent has identified 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.
Under 16 05 06* the bottle leaves in a lab pack, grouped with other toxic stock and kept apart from oxidisers and acids. On your list, write the name in full and avoid DMS, which is easily read as dimethyl sulfide or confused with DMSO, and a wrong description here puts the packer at real risk. Record the bottle size, how much remains and the state of the closure. Related alkylating reagents from the same research group should each get their own line. Old bench habits of deactivating residues must not be applied to this bottle, and no amount goes near a sink, a drain or a general waste bin.
| EWC code, laboratory chemicals | 16 05 06* |
|---|---|
| Discarded organic chemical, not a laboratory pack | 16 05 08* |
| 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 stock.
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.
- H314 Causes severe skin burns and eye damage.
- H317 May cause an allergic skin reaction.
- H330 Fatal if inhaled.
- H335 May cause respiratory irritation.
- H341 Suspected of causing genetic defects.
- H350 May cause cancer.
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.
- P270 Do not eat, drink or smoke when using this product.
- P271 Use only outdoors or in a well-ventilated area.
- P272 Contaminated work clothing should not be allowed out of the workplace.
- P280 Wear protective gloves, protective clothing, eye protection and face protection.
- P284 In case of inadequate ventilation wear respiratory protection.
- P301+P316 IF SWALLOWED: Get emergency medical help immediately.
- P301+P330+P331 IF SWALLOWED: Rinse mouth. Do NOT induce vomiting.
- P302+P352 IF ON SKIN: Wash with plenty of water.
- P302+P361+P354 IF ON SKIN: Take off immediately all contaminated clothing. Immediately rinse with water for several minutes.
- P304+P340 IF INHALED: Remove person to fresh air and keep comfortable for breathing.
- P305+P354+P338 IF IN EYES: Immediately rinse 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.
- P320 Specific treatment is urgent (see supplemental first aid instruction on this label).
- P321 Specific treatment (see supplemental first aid instruction on this label).
- P330 Rinse mouth.
- P333+P317 If skin irritation or rash occurs: Get medical help.
- P362+P364 Take off contaminated clothing. And wash it before reuse.
- P363 Wash contaminated clothing 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.
- P262 Do not get in eyes, on skin, or on clothing.
- P264+P265 Wash hands and exposed skin thoroughly after handling. Do not touch eyes.
- P305+P351+P338 IF IN EYES: Rinse cautiously with water for several minutes. Remove contact lenses, if present and easy to do. Continue rinsing.
- P317 Get medical help.
- P319 Get medical help if you feel unwell.
- P337+P317 If eye irritation persists: Get medical help.
- P361+P364 Take off immediately all contaminated clothing. And wash it before reuse.
Substance as classified, dilutions may differ.
Questions
We found a small old bottle in a departed researcher's cupboard. What should happen first?
Leave it where it stands and restrict access to that cupboard. Tell your safety lead, note what the label says and how the closure looks, and ask for a specialist collection. Small size does not lower the concern, given that inhalation of this liquid can be fatal.
Can it share a locked cabinet with our other carcinogens?
It can sit with other locked toxic stock, provided acids and oxidisers are kept out of that cabinet. Give it its own tray so that a failed closure cannot reach neighbouring bottles, and make sure the stock record shows who is responsible for it.
Is an apparently empty bottle still a problem?
Yes. A film of residue on the glass and in the cap thread can still give off vapour, and the classification still applies to what remains. Keep the cap on and send it for collection as you would a part full bottle, rather than rinsing it out.
How can we tell whether an old bottle has gone off?
Usually you cannot by looking at it, and the quality of the contents is not the question once it is surplus. The closure and label tell you whether it can stay on the shelf safely until collection. If either has failed, get specialist advice before anyone handles it.
