Sulfosalicylic acid (CAS 97-05-2): storage and disposal
Pathology and university labs hold sulfosalicylic acid as a solid, mostly as a protein precipitant at the bench. It is classified as a skin and eye irritant, and as an acid it belongs in the corrosive store rather than the general chemicals cupboard. Its place among the other acids on the shelf, and the hazardous waste classification, decide how it is grouped and collected.
- CAS number
- 97-05-2
- Form
- Solid
- Storage class
- Acid
- Signal word
- Warning
- Usual EWC code
- 16 05 06*
Harmful or irritant
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
Look at the cap thread before anything else. A solid acid with crystals caught in the thread seals badly, and damp then draws in and sets the cap to the neck. Sulfosalicylic acid sits low down on an acid-resistant tray in a ventilated corrosive store, with alkalis kept on a separate shelf because the two react with heat and spattering. Oxidisers stay apart as well, since many of them become unstable on contact with acid. Pathology stores often have a small working jar near the bench and a larger sealed jar elsewhere. Date both, and keep the working jar from creeping onto a general reagent shelf where the acid label gets overlooked.
How to tell it has deteriorated
Crust around the neck is the first thing a technician sees on an old jar of this solid. It may indicate deposited crystals, fine dust, moisture or a poor seal, and the cap may be difficult to remove. Look next at the shelf under the jar and at any metal fittings nearby, because acid residue attacks them over time. Crystals that have clumped or turned damp suggest the container has been opened in humid air. A cracked jar or a label that has faded under acid residue should be noted. Beyond these general checks the solid gives few visible signs of its own, so an unreadable label matters more than any colour change.
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.
Nothing about this acid should be sorted out locally: it must not go down a sink, into general waste or a skip, and nobody should try to neutralise or dilute it first. Record the container size, whether it is the solid or a made-up solution, and the state of the cap. Pathology departments usually fall under the healthcare waste code, while university chemistry stores more often use the laboratory chemical code. The acid is packed with other compatible acids in a lab pack, away from alkalis, oxidisers and solvents, by the specialist carrier.
| 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 |
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.
- Calcium hypochloriteMany oxidisers release toxic gas or become unstable in contact with acid.
- 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.
- Hydrogen peroxideMany oxidisers release toxic gas or become unstable in contact with acid.
- Mercury(II) chlorideToxic stock is stored apart from acids. Several toxic salts release toxic gas in contact with acid.
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- MethanolOxidising acids can ignite flammable materials, and acid fumes attack containers and seals.
- Potassium hydroxideAcids and alkalis react with strong heat and spattering if they meet.
- Potassium nitrateMany oxidisers release toxic gas or become unstable in contact with acid.
- Potassium permanganateMany oxidisers release toxic gas or become unstable in contact with acid.
- Sodium cyanideToxic stock is stored apart from acids. Several toxic salts release toxic gas in contact with acid.
- Sodium hydroxideAcids and alkalis react with strong heat and spattering if they meet.
- TolueneOxidising acids can ignite flammable materials, and acid fumes attack containers and seals.
Common quantities we collect
Usually held as: solid, dihydrate.
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
- H315 Causes skin irritation.
- H319 Causes serious eye irritation.
Precautionary statements
- P264 Wash hands and exposed skin thoroughly after handling.
- P264+P265 Wash hands and exposed skin thoroughly after handling. Do not touch eyes.
- P280 Wear protective gloves, protective clothing, eye protection and face protection.
- P302+P352 IF ON SKIN: Wash with plenty of water.
- P305+P351+P338 IF IN EYES: Rinse cautiously with water for several minutes. Remove contact lenses, if present and easy to do. Continue rinsing.
- P321 Specific treatment (see supplemental first aid instruction on this label).
- 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.
Substance as classified, dilutions may differ.
Questions
Can leftover sulfosalicylic acid from urine protein testing go in the clinical waste stream?
No. It is a chemical waste classified as an eye and skin irritant, so it is described as hazardous chemical waste and collected by specialist carrier. Clinical or sharps bins are not suitable, and the pathology waste code only changes how it is described on paperwork.
Where should it sit relative to our other acids?
On the same low acid-resistant tray or shelf as other acids, in the ventilated corrosive store, and away from alkalis, oxidisers and solvents. Keep the cap clean so the neck does not crust, and date the jar when it arrives.
How do we know if an old jar is still usable?
Check the cap, the neck and the label first. Heavy crust, damp clumps or an unreadable label mean you should stop using it and book collection. The solid shows few visible changes, so do not rely on colour alone.
