Tin metal (CAS 7440-31-5): storage and disposal

Tin turns up in school and college preparation rooms as granules or foil, and in university stores as the odd forgotten jar. It is not classified as hazardous on the sources we checked, but it remains a chemical waste that needs an accurate description. What decides handling is less the tin itself than what shares its shelf: strong alkalis, hydrogen peroxide and the picric acid family.

CAS number: 7440-31-5
Form: Solid
Storage class: General
Usual EWC code: 16 05 09

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 general 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

Granules usually come in a wide-necked jar and foil in a flat packet or tube, so the first check is that the label says which form it is. A dry shelf in the general store is suitable, dated on arrival. Keep tin away from sodium hydroxide and potassium hydroxide, because strong alkalis release flammable hydrogen with these metals. Hydrogen peroxide is another neighbour to avoid, since metals speed its breakdown and release oxygen and pressure. Picric acid, Bouin's fluid and ammonium picrate form shock sensitive picrates with metals, and sodium azide forms shock sensitive azides with several metals, so tin needs its own space away from all of them.

How to tell it has deteriorated

Tin gives very few visible signs of age. The metal may lose its shine and otherwise sits unchanged for long periods, so the container tells you more than the contents do. Look for a label that has faded or lifted, a lid that is cracked or stuck, a jar that has lost its date of receipt and any staining from a neighbour that has leaked. Foil can crease and flake at the folds, which is cosmetic. If granules are caked with something white or coloured, or sit in a jar with an unknown residue, assume contamination and record it as unidentified material rather than clean tin.

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 non-regulated or low hazard laboratory pack with compatible chemicals.

Before asking for a collection, write down the form, how much is left and whether the jar is the original or a refill from another bottle. Tin is not classified as hazardous on the sources we checked, so it takes the plain code 16 05 09 and a waste transfer note, though it is still described as a chemical. It goes only by specialist collector, and it must not be put in a sink, a drain, an ordinary bin or a skip. Nobody should try to melt or dissolve it beforehand. It is packed in its own compatible group, apart from alkalis and hydrogen peroxide. Jars contaminated with alkali residue should be declared as such.

Waste codes and transport details for Tin metal
EWC code, laboratory chemicals	16 05 09
Hazardous waste	No

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

Named chemicals to keep apart

Ammonium picratePicric acid forms shock sensitive metal picrates with metals.
Hydrogen peroxideMetals speed the breakdown of hydrogen peroxide, releasing oxygen and pressure.
Picric acidPicric acid forms shock sensitive metal picrates with metals.
Potassium hydroxideStrong alkalis release flammable hydrogen with these metals.
Sodium azideAzides form shock sensitive metal azides with lead, copper, brass and similar metals.
Sodium hydroxideStrong alkalis release flammable hydrogen with these metals.

Common quantities we collect

Usually held as: granules, foil.

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

Questions

Does old tin foil or granule stock expire?

Tin gives few signs of age, and no fixed life is set for it. Judge the container rather than the metal: a legible label, an intact lid and a known date of receipt matter most. Stock with an unknown history or sticky residue should be recorded as unidentified before collection.

Can tin share a shelf with sodium hydroxide pellets?

No. Strong alkalis such as sodium hydroxide and potassium hydroxide release flammable hydrogen with these metals. Keep tin and alkali stock in separate cupboards, with the alkali low down on resistant trays in a corrosive store.

Is tin metal hazardous waste?

It is not classified as hazardous on the sources we checked, which is why it takes the code without an asterisk. It is still a chemical waste, so it needs an accurate description and a specialist collection, and it must not go in the school bin.