Sulfuric acid (CAS 7664-93-9): storage and disposal
Sulfuric acid sits in school and college prep rooms, university labs and pathology and histology departments, most often as 0.5 M and 1 M solutions with a bottle of concentrated 98% behind them. It causes severe skin burns and eye damage. The concentrated liquid is a strong dehydrating acid, so its strength, how long the cap has been off and what it has been kept beside decide how it is handled and collected.
- CAS number
- 7664-93-9
- Form
- Solution
- Storage class
- Acid
- Signal word
- Danger
- Usual EWC code
- 16 05 06*
Corrosive
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
Severe burns decide where this acid goes: low down, on an acid-resistant tray, in a ventilated corrosive store. Concentrated 98% stock takes up moisture, so keep the cap fitted, because the level can rise in an open bottle. Keep glycerol and other organic materials away from it, since the concentrated acid reacts violently with them and chars them. Potassium chlorate must be elsewhere, because chlorates and strong acids can form explosive chlorine dioxide. Potassium cyanide, ferricyanides, sulfides and hypochlorites all give off toxic gas in contact with acids, so they belong in their own cabinets or spaces. Prep room shelves holding the 0.5 M and 1 M solutions follow the same rule.
How to tell it has deteriorated
An open bottle of concentrated stock slowly takes up moisture from the air, so the level can creep upward instead of falling. A dark colour points to contamination, and organic material that gets in is charred. Other warning signs are a perished cap and white crust around the neck, which show the closure has been attacked or the liquid has crept out. The 0.5 M and 1 M solutions look like water for their whole life, so for those bottles the label, the cap and any crust or staining on the tray are the evidence. A bottle with a crusted neck or a seized cap should be left as it is and flagged for collection.
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.
Only specialist collection takes the acid away. A sink, a drain, general waste and a skip are all ruled out, and it must not be diluted or treated beforehand. Tell the collector whether each bottle holds concentrated acid or a weaker solution, whether it has darkened and whether the cap or neck is damaged. A dark bottle may hold charred organic contamination, and a crusted neck makes a bottle awkward to lift, so both are worth recording before the visit. List sulfuric acid separately from glycerol, cyanides, sulfides, chlorates, hypochlorites and other incompatible chemicals. The specialist collector determines its compatible packing group. Hold on to the consignment note you are given, which is hazardous waste paperwork.
| 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
- 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.
- GlycerolConcentrated sulfuric acid reacts violently with these materials.
Show 16 more
- HexaneOxidising acids can ignite flammable materials, and acid fumes attack containers and seals.
- Hydrogen peroxideMany oxidisers release toxic gas or become unstable in contact with acid.
- Iron(II) sulfideSulfides release toxic hydrogen sulfide gas with acids.
- 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 permanganatePermanganate can ignite or explode with these materials.
- 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.
- SucroseConcentrated sulfuric acid reacts violently with these materials.
Common quantities we collect
Usually held as: 0.5 M, 1 M, concentrated (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
- H314 Causes severe skin burns and eye damage.
Precautionary statements
- P260 Do not breathe dust, fume, gas, mist, vapours or spray.
- P264 Wash hands and exposed skin thoroughly after handling.
- 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.
- 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 the level in our concentrated sulfuric acid bottle gone up?
Concentrated stock takes up moisture from the air, so the level can rise in a bottle that has been left open or poorly capped. Fit the cap properly, keep the bottle upright, and list it for collection if the liquid has darkened or the cap is damaged.
What does a dark colour in sulfuric acid mean?
A dark colour is a warning sign of contamination, and the concentrated acid chars organic material that gets into it. Do not try to clean it up or pour it away. Keep it capped on its tray and arrange specialist collection.
Can sulfuric acid be stored with the other acids?
Yes, on acid-resistant trays low down in a ventilated corrosive store, but not beside glycerol, potassium chlorate, cyanides, sulfides or hypochlorites. Those react with it or release toxic gas, so they need their own space.
Do weaker sulfuric acid solutions still need specialist collection?
Yes. A weaker solution may be less hazardous than the concentrated acid, but it remains chemical waste. It does not go into a sink, drain or general waste, and it should not be treated first. It goes with the rest of the acids by specialist collection.
