Lactic acid (CAS 50-21-5): storage and disposal
Lactic acid is held as a viscous liquid of about 90% in school and college prep rooms, university labs and pathology and histology departments. It causes skin irritation and serious eye damage. A bottle of concentrated stock tends to be used a little at a time over many years, so the cap, the neck and the label tell a holder more about its state than the liquid itself.
- CAS number
- 50-21-5
- Form
- Liquid
- 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
Serious eye damage decides where this bottle goes: low down on an acid-resistant tray, never at eye level on an open shelf where a drip or a slip would reach a face. The concentrated liquid is viscous and clings to the thread of the cap, which is how the neck gets sticky and the cap gets stuck. Do not force a stuck cap. Keep it in a ventilated corrosive store, away from alkalis and oxidisers, and clear of solvents. Pathology and histology benches should keep it off the working surface and in the store between uses.
How to tell it has deteriorated
Check the bottle first, then the liquid. A sticky or crusted neck, a cap that has seized and drips down the outside are the commonest faults, because the viscous liquid creeps into the thread. Look also for a perished cap, a cracked container, corrosion on nearby fittings and a label that has been stained or has faded. Lactic acid gives few visible signs of age in the liquid itself, so a change in colour or the presence of anything floating is worth noting rather than ignoring. A bottle with a stuck cap or an unreadable strength should be left upright and listed 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.
As a discarded organic chemical that is not in a lab pack, the code that fits is 16 05 08*. Grouping matters: the collector packs it with other organic acids and keeps it away from alkalis and oxidisers, so it is helpful to list those separately. It must never be poured into a sink or drain or put into a bin or skip, and it must not be diluted or neutralised first. Record the strength on the label, the volume left and whether the cap is stuck, because a sticky bottle is awkward to lift. In a healthcare setting such as a pathology department, the code is 18 01 06*.
| 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.
Show 7 more
- 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: about 90%.
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.
- H318 Causes serious eye damage.
Precautionary statements
- P260 Do not breathe 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.
- P280 Wear protective gloves, protective clothing, eye protection and face protection.
- 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.
- P317 Get medical help.
- P321 Specific treatment (see supplemental first aid instruction on this label).
- P332+P317 If skin irritation occurs: Get medical help.
- P362+P364 Take off contaminated clothing. And wash it before reuse.
- 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 is the cap on our lactic acid bottle stuck?
The concentrated liquid is viscous and creeps into the thread, drying into a sticky crust. Do not force the cap and do not clean it dry. Leave the bottle upright on its tray, record the problem and list it for collection.
Why should lactic acid not be kept at eye level?
It causes serious eye damage and skin irritation, and a viscous liquid is hard to wipe up. Low down on an acid-resistant tray, a drip or a break is less likely to reach a face.
Does a bottle of lactic acid expire?
No shelf life is given. Check for a stuck or perished cap, a crusted neck, a cracked container, a stained label and any change in colour. A bottle with any of those, or an unknown date of receipt, should go on the collection list.
