Formic acid (CAS 64-18-6): storage and disposal
Sharp smelling and colourless, formic acid is an organic acid usually bought at about 90% or 98%. Schools and colleges keep small bottles in the prep room acid store, universities use it in teaching and research labs, and histology departments may hold it for decalcifying bone. Two things decide how it is handled: it is flammable as well as corrosive, and concentrated stock slowly gives off carbon monoxide, so the age of a bottle matters.
- CAS number
- 64-18-6
- Form
- Liquid
- Storage class
- Acid
- Signal word
- Danger
- Usual EWC code
- 16 05 06*
Flammable
Corrosive
Acute toxicity
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 in a school or lab
In a school prep room the bottle normally lives low down in the ventilated corrosive store, on an acid-resistant tray. Placement needs more thought than for most acids because it is flammable too, so ignition sources stay well away, and so do oxidising acids such as nitric acid. Calcium hypochlorite, iron(II) sulfide and potassium cyanide do not belong near it, since acid contact can release chlorine, hydrogen sulfide or hydrogen cyanide. Alkalis go on another shelf. It also attacks metal, so look at brackets and fittings close by. Write the date of receipt on each bottle, because pressure builds slowly in concentrated stock and the date is what tells you to act. Where a bottle came with a vented cap, leave that cap in place and keep the bottle upright.
How to tell it has deteriorated
Good stock is a clear, colourless, free-flowing liquid with a sharp smell. The 98% grade can also freeze into colourless crystals in a cold store, which is a property of the acid and no sign of age, though it should never be warmed. The warning sign that matters is a bulging bottle. Concentrated acid decomposes slowly into carbon monoxide, which has nowhere to go behind a sealed cap. Perished or brittle caps, a crust around the neck and corroded fittings nearby also deserve attention. Carbon monoxide has no colour, so an undated bottle with flat sides can still be under pressure. If a bottle is old, undated or swollen, do not open it, do not move it and do not loosen the cap. Ask for a specialist assessment instead.
Decomposes slowly to carbon monoxide, and sealed bottles can build pressure.
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 corrosive acid laboratory pack with compatible chemicals.
It leaves by specialist collection, with a registered carrier taking it to a permitted site, and no other route exists. It does not go into a sink, a drain, a general waste bin or a skip, and nobody should try to treat it first. Record the strength shown on the label, the date of receipt and anything visibly wrong with the bottle. Being an organic acid that is also flammable, it is kept out of any lab pack group holding oxidising acids. A swollen bottle must be declared beforehand, as it may need assessing where it stands. Schools and universities normally use code 16 05 06*, whereas a hospital histology lab uses 18 01 06*. List used decalcifying solutions separately from the concentrated bottles.
| 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 |
20 01 13* (solvents) belongs to municipal collections and is shown for reference only. It is not the normal code for a laboratory collection.
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
- FlammableOxidising acids can ignite flammable materials, and acid fumes attack containers and seals.
- AlkaliAcids and alkalis react with strong heat and spattering if they meet.
- OxidiserMany oxidisers release toxic gas or become unstable in contact with acid.
- ToxicToxic stock is stored apart from acids. Several toxic salts release toxic gas in contact with acid.
Named chemicals to keep apart
- AcetoneOxidising acids can ignite flammable materials, and acid fumes attack containers and seals.
- Ammonia solutionAcids and alkalis react with strong heat and spattering if they meet.
- Ammonium sulfide solutionSulfides release toxic hydrogen sulfide gas with acids.
- Calcium hypochloriteHypochlorites release toxic chlorine gas in contact with acids.
- Chloramine THypochlorites release toxic chlorine gas in contact with acids.
- EthanolOxidising acids can ignite flammable materials, and acid fumes attack containers and seals.
- FormalinToxic stock is stored apart from acids. Several toxic salts release toxic gas in contact with acid.
- HexaneOxidising acids can ignite flammable materials, and acid fumes attack containers and seals.
Show 16 more
- Hydrogen peroxideMany oxidisers release toxic gas or become unstable in contact with acid.
- Iron(II) sulfideSulfides release toxic hydrogen sulfide gas with acids.
- Mercury(II) chlorideToxic stock is stored apart from acids. Several toxic salts release toxic gas in contact with acid.
- MethanolOxidising acids can ignite flammable materials, and acid fumes attack containers and seals.
- Potassium chlorateChlorates and strong acids can form explosive chlorine dioxide.
- Potassium cyanideCyanides release highly toxic hydrogen cyanide gas with acids.
- Potassium ferricyanideHeating or strong acids can release toxic hydrogen cyanide from these complexes.
- Potassium ferrocyanideHeating or strong acids can release toxic hydrogen cyanide from these complexes.
- Potassium hydroxideAcids and alkalis react with strong heat and spattering if they meet.
- Sodium azideAzides release highly toxic and explosive hydrazoic acid with acids.
- Sodium chlorateChlorates and strong acids can form explosive chlorine dioxide.
- Sodium cyanideCyanides release highly toxic hydrogen cyanide gas with acids.
- Sodium dichloroisocyanurateHypochlorites release toxic chlorine gas in contact with acids.
- Sodium hypochloriteHypochlorites release toxic chlorine gas in contact with acids.
- Sodium nitriteNitrites release toxic nitrogen oxides with acids.
- Sodium sulfideSulfides release toxic hydrogen sulfide gas with acids.
Common quantities we collect
Usually held as: about 90%, 98%.
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
- H226 Flammable liquid and vapour.
- H290 May be corrosive to metals.
- H302 Harmful if swallowed.
- H314 Causes severe skin burns and eye damage.
- H331 Toxic if inhaled.
Precautionary statements
- P210 Keep away from heat, hot surfaces, sparks, open flames and other ignition sources. No smoking.
- P233 Keep container tightly closed.
- P234 Keep only in original packaging.
- P240 Ground and bond container and receiving equipment.
- P241 Use explosion-proof electrical, ventilating and lighting equipment.
- P242 Use non-sparking tools.
- P243 Take action to prevent static discharges.
- 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.
- P301+P330+P331 IF SWALLOWED: Rinse mouth. Do NOT induce vomiting.
- P302+P361+P354 IF ON SKIN: Take off immediately all contaminated clothing. Immediately rinse with water for several minutes.
- P303+P361+P353 IF ON SKIN (or hair): Take off immediately all contaminated clothing. Rinse skin with water or shower.
- 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.
- P317 Get medical help.
- P321 Specific treatment (see supplemental first aid instruction on this label).
- P330 Rinse mouth.
- P363 Wash contaminated clothing before reuse.
- P370+P378 In case of fire: Use suitable extinguishing media to extinguish.
- P390 Absorb spillage to prevent material damage.
- P403+P233 Store in a well-ventilated place. Keep container tightly closed.
- P403+P235 Store in a well-ventilated place. Keep cool.
- P405 Store locked up.
- P406 Store in corrosive resistant container with a resistant inner liner.
- P501 Dispose of contents and container in accordance with local, regional, national and international regulations.
Substance as classified, dilutions may differ.
Questions
Our bottle of formic acid has bulged. Should we release the pressure?
No. Leave the cap alone and do not move the bottle. The swelling means gas has built up inside, and opening or handling it could release carbon monoxide and corrosive liquid together. Keep people away from that shelf and arrange a specialist assessment, mentioning the bulge when you make contact.
Does formic acid go in the flammables cabinet or with the other acids?
It is stored as an acid, low down in the ventilated corrosive store, even though it is also flammable. That makes ignition sources a concern in the acid store. The separation that matters most is from oxidising acids and other oxidisers, which should never share its tray or shelf.
Is used decalcifying solution from histology the same waste as the concentrated bottle?
It is still a chemical waste for specialist collection, but describe it as what it is: a working solution, with its approximate make-up and any fixative or tissue contact noted. A weaker solution may be less hazardous than the concentrated acid, though that does not make it safe.
How do we judge a formic acid bottle with no date on it?
There is no way to judge it from the outside, because the gas that builds up cannot be seen and flat sides prove little. Treat an undated bottle as old. Do not open or move it, and ask for a specialist assessment before anyone handles it.
