Nitric acid (CAS 7697-37-2): storage and disposal
Nitric acid is held in school prep rooms, colleges, university labs and pathology and histology departments, as 1 M and 2 M solutions and concentrated stock of about 70%. It is a strong oxidising acid that may intensify fire, causes severe burns and is toxic if inhaled. Its worst partners are organic solvents, so what it is stored near and what ends up in a waste bottle decide how it is handled.
- CAS number
- 7697-37-2
- Form
- Solution
- Storage class
- Acid
- Signal word
- Danger
- Usual EWC code
- 16 05 06*
Oxidising
Corrosive
Acute toxicity
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 acid 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 school prep room, this acid belongs in its own segregated space rather than on the general acid shelf. Hold it in glass, with caps that resist nitric acid. Acetone, ethanol, ethyl acetate and other organic solvents must be kept apart from it, because it reacts violently with them, can ignite them and can build pressure in a closed bottle. Acetic anhydride can react explosively with it, and acetic acid has to stay clear as well. Formalin, hypochlorites and sulfides need other shelves, since acids release toxic gas from several of them. The oxidising character rules out a flammables cabinet, and it also shares nothing with the alkali shelf.
How to tell it has deteriorated
Fresh concentrated stock is clear, so the first thing to notice is a yellow or brown tint. Light drives that change as nitrogen oxides form, and a bottle that has darkened has been standing in light or for a long time. Brown fumes in the neck, a brittle cap and a bulging bottle are the stronger warnings, and bulging means pressure is building inside. Weaker solutions show less, so check the cap, the label and the shelf. A bulging or fuming bottle should not be opened or carried across the room: leave it where it is, keep people clear and ask for specialist advice.
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.
Away from the site, stock travels only by specialist collection. It must never be poured into a sink or drain or put in general waste, and nobody should try to dilute or neutralise it first. The instruction that matters most is never to add it to a solvent waste bottle, because waste bottles mixing it with organics are a known cause of laboratory explosions. Record the strength, the container and whether any bottle has ever received waste. It is described as hazardous laboratory pack stock under waste code 16 05 06*. The specialist collector determines a compatible packing arrangement for nitric acid, keeping it segregated from organic liquids and other incompatible chemicals. Keep the consignment paperwork afterwards.
| EWC code, laboratory chemicals | 16 05 06* |
|---|---|
| Discarded inorganic chemical, not a laboratory pack | 16 05 07* |
| 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
- 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
- Acetic anhydrideAcetic anhydride can react explosively with these oxidisers.
- AcetoneNitric acid reacts violently with organic solvents and can ignite them or build pressure in waste bottles.
- 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.
- EthanolNitric acid reacts violently with organic solvents and can ignite them or build pressure in waste bottles.
- Ethyl acetateNitric acid reacts violently with organic solvents and can ignite them or build pressure in waste bottles.
- FormalinFormaldehyde reacts with these materials. With hydrochloric acid it can form a potent carcinogen.
Show 14 more
- HexaneNitric acid reacts violently with organic solvents and can ignite them or build pressure in waste bottles.
- Iron(II) sulfideSulfides release toxic hydrogen sulfide gas with acids.
- IsopropanolNitric acid reacts violently with organic solvents and can ignite them or build pressure in waste bottles.
- MercuryMercury forms amalgams or unstable compounds with these materials.
- MethanolNitric acid reacts violently with organic solvents and can ignite them or build pressure in waste bottles.
- 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.
- 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.
Common quantities we collect
Usually held as: 1 M, 2 M, concentrated (about 70%).
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
- H272 May intensify fire; oxidiser.
- 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.
- P220 Keep away from clothing and other combustible materials.
- 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.
- P271 Use only outdoors or in a well-ventilated area.
- P280 Wear protective gloves, protective clothing, eye protection and face protection.
- 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.
- 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.
- P321 Specific treatment (see supplemental first aid instruction on this label).
- P363 Wash contaminated clothing before reuse.
- P370+P378 In case of fire: Use suitable extinguishing media to extinguish.
- 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
Why has our nitric acid turned yellow or brown?
Concentrated stock turns yellow or brown with light as nitrogen oxides form. Treat a darkened bottle as ageing stock, keep the cap on, check the neck and cap for damage, and keep it apart from solvents while you arrange collection.
Can nitric acid waste go in the solvent waste bottle?
No. It reacts violently with organic solvents and can ignite them or burst the bottle, and such waste bottles are a known cause of laboratory explosions. Keep nitric acid in its own container and do not add it to any solvent waste.
What should we do about a bottle that is bulging?
Do not open it and do not move it more than you must. Bulging shows pressure building. Keep people clear, and ask for specialist advice and a store assessment before anyone handles it.
Can it be kept in the flammables cabinet to save space?
No. It may intensify fire and ignites some organic solvents on contact, so it needs its own segregated space away from flammable stock. Use glass bottles with caps that resist nitric acid.
