Sodium silicate (CAS 1344-09-8): storage and disposal
School, college and university stores hold sodium silicate as waterglass, a thick colourless liquid used for chemical garden demonstrations and similar teaching. It is classified Danger for severe skin burns and eye damage, and it may irritate the respiratory system. What catches holders out is how it behaves on the neck of the bottle: it sets to a hard film that fixes caps and stoppers in place.
- CAS number
- 1344-09-8
- Form
- Solution
- Storage class
- Alkali
- Signal word
- Danger
- Usual EWC code
- 16 05 06*
Corrosive
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 alkali 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
Waterglass usually arrives in a plastic bottle, and plastic with a screw cap is the right container. Glass stoppers are the problem: the liquid dries on the ground glass and sets hard, so a stopper can seize for good. Keep it low on a resistant tray in the alkali store, and keep the rim clean, since a dry rim is easier to open next time. Hydrofluoric acid must be kept well apart, because it attacks glass and silicates, releasing toxic gas. Acids belong in a different place in any case, as acids and alkalis react with heat and spattering.
How to tell it has deteriorated
Waterglass gives itself away at the neck. A white or glassy crust around the rim, a cap that will not turn and a stopper fused to the bottle are the usual signs. Left open, it forms a skin on the surface and may thicken or set into a jelly like or solid mass, because it reacts with carbon dioxide from the air. Do not force a stuck closure. A bottle with a crusted neck, a changed texture or a faded label should be recorded as it is, kept upright on a tray and described to the collector.
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 alkali laboratory pack with compatible chemicals.
Waste code 16 05 06* marks it as hazardous waste, and the Danger classification for burns is the reason. It must not go into a sink, a drain, a general waste bin or a skip: waterglass can set hard, which is an extra reason it must never be washed away, and nobody should neutralise or treat it first. Specialist collection takes it with other alkalis, away from acids and from hydrofluoric acid. Record the container material, its size, and whether the neck is crusted or the stopper is seized, so the collector brings suitable packaging.
| EWC code, laboratory chemicals | 16 05 06* |
|---|---|
| Discarded inorganic chemical, not a laboratory pack | 16 05 07* |
| 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
- AcidAcids and alkalis react with strong heat and spattering if they meet.
- OxidiserSome oxidisers react strongly with alkalis, and ammonia based stock is especially at risk.
Named chemicals to keep apart
- Acetic acidAcids and alkalis react with strong heat and spattering if they meet.
- Calcium hypochloriteSome oxidisers react strongly with alkalis, and ammonia based stock is especially at risk.
- Hydrochloric acidAcids and alkalis react with strong heat and spattering if they meet.
- Hydrofluoric acidHydrofluoric acid attacks glass and silicates, releasing toxic gas.
- Hydrogen peroxideSome oxidisers react strongly with alkalis, and ammonia based stock is especially at risk.
- Nitric acidAcids and alkalis react with strong heat and spattering if they meet.
- Potassium nitrateSome oxidisers react strongly with alkalis, and ammonia based stock is especially at risk.
- Potassium permanganateSome oxidisers react strongly with alkalis, and ammonia based stock is especially at risk.
Show 1 more
- Sulfuric acidAcids and alkalis react with strong heat and spattering if they meet.
Common quantities we collect
Usually held as: waterglass.
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.
- H335 May cause respiratory irritation.
Precautionary statements
- 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.
- P319 Get medical help if you feel unwell.
- P321 Specific treatment (see supplemental first aid instruction on this label).
- P363 Wash contaminated clothing before reuse.
- 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
Our sodium silicate bottle has a stuck stopper. What now?
Leave it. Waterglass dries into a hard film on the ground glass, and forcing it risks breaking the neck. Record the bottle, keep it upright in a tray and tell the collector the stopper is seized when you book.
Why has the waterglass thickened or gone lumpy?
It reacts with carbon dioxide from the air, and the surface sets to a skin or gel. This means the bottle has not been sealed well. The stock is no longer in its original condition, so record it and hold it for collection.
Can it share a shelf with hydrofluoric acid?
No. Hydrofluoric acid attacks glass and silicates, releasing toxic gas, so keep the two well apart. Acids and alkalis should also be separated as a general rule.
