Lead citrate (CAS 512-26-5): storage and disposal
Lead citrate is held by university electron microscopy units and histology services as a contrast stain, usually in small amounts that last for years. It is classified as harmful if swallowed or inhaled, as able to damage the unborn child and suspected of damaging fertility, as causing organ damage through repeated exposure and as very toxic to aquatic life. Small quantities do not make it a lesser waste.
- CAS number
- 512-26-5
- Form
- Solid
- Storage class
- Toxic
- Signal word
- Danger
- Usual EWC code
- 16 05 06*
Harmful or irritant
Serious health hazard
Hazardous to the environment
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 toxic 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
In a microscopy suite the stain tends to sit near the grid-staining bench alongside uranyl and buffer stocks, and the point to get right is separation. Keep the lead citrate in a locked toxic cabinet with a stock record, away from incompatible reagents, including acids and oxidising reagents. A histology store should not file it with routine stains on an open rack. Stain made from the solid and left in tubes is the real housekeeping problem, so label every tube with its content and date and keep it in the same cabinet as the solid. Keep containers tightly closed.
How to tell it has deteriorated
In stain work, the giveaway is a fine white precipitate. Lead citrate reacts with carbon dioxide from the air to form lead carbonate, so a stain tube or a poorly closed bottle that has stood open develops a cloudy deposit or a crust at the surface. Treat that as a sign that the stain has been spoilt. The solid itself should be a clean, dry, free-flowing white powder, so lumps, damp or discolouration are worth recording. Other warnings are an illegible label, tubes with no date and a stock record that does not match what is in the cabinet.
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 toxic laboratory pack with compatible chemicals.
A university lab and a hospital histology department will use different codes. A laboratory pack takes 16 05 06*, discarded organic chemical outside a laboratory pack takes 16 05 08*, and a human healthcare setting takes 18 01 06*, so say which describes your service. Describe solid and made-up stain separately, with approximate volumes, and keep both sealed in their labelled containers. Used grids and spent stain must not go down a sink or into clinical waste, and nobody should try to precipitate or filter the stain to reduce it. The carrier packs the lead stock apart from acids and oxidisers on a specialist collection.
| 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
- OxidiserToxic and oxidising stock are stored apart. A reaction could release toxic vapours.
- AcidToxic stock is stored apart from acids. Several toxic salts release toxic gas in contact with acid.
Named chemicals to keep apart
- Acetic acidToxic stock is stored apart from acids. Several toxic salts release toxic gas in contact with acid.
- Calcium hypochloriteToxic and oxidising stock are stored apart. A reaction could release toxic vapours.
- Hydrochloric acidToxic stock is stored apart from acids. Several toxic salts release toxic gas in contact with acid.
- Hydrogen peroxideToxic and oxidising stock are stored apart. A reaction could release toxic vapours.
- Nitric acidToxic stock is stored apart from acids. Several toxic salts release toxic gas in contact with acid.
- Potassium nitrateToxic and oxidising stock are stored apart. A reaction could release toxic vapours.
- Potassium permanganateToxic and oxidising stock are stored apart. A reaction could release toxic vapours.
- Sulfuric acidToxic stock is stored apart from acids. Several toxic salts release toxic gas in contact with acid.
Common quantities we collect
Usually held as: electron microscopy stain.
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
- H302 Harmful if swallowed.
- H332 Harmful if inhaled.
- H360Df May damage the unborn child. Suspected of damaging fertility.
- H373 May cause damage to organs through prolonged or repeated exposure.
- H410 Very toxic to aquatic life with long lasting effects.
Substance as classified, dilutions may differ.
Questions
What should happen to spent lead citrate stain?
It must never go down a sink. It is classified as very toxic to aquatic life and as able to damage fertility and the unborn child. Collect spent stain in a sealed, labelled container and request specialist collection.
Why has the stain developed a white deposit?
Lead citrate reacts with carbon dioxide in air to form a white lead carbonate precipitate. It means the stain is spoilt and should be set aside as waste, not filtered or used again.
Which waste code applies in a hospital histology lab?
A human healthcare setting uses 18 01 06*. A laboratory pack elsewhere uses 16 05 06*, and discarded organic chemical outside a pack uses 16 05 08*. State the setting when you ask for a collection.
How should old unlabelled stain tubes be handled?
Keep them closed, upright and in a tray in the locked cabinet. Record where they were found and send an enquiry. Do not open them to check, since the contents must be described accurately.
