Lead(II) chromate (CAS 7758-97-6): storage and disposal
A bright yellow lead and chromium(VI) compound, lead(II) chromate survives mostly as legacy pigment stock in school, college and university stores, often under the name chrome yellow. It may cause cancer, may damage the unborn child and is suspected of damaging fertility. Repeated exposure may harm organs, and it is very toxic to aquatic life. Age changes none of this, so an old jar is handled as current hazardous stock.
- CAS number
- 7758-97-6
- Form
- Solid
- Storage class
- Toxic
- Signal word
- Danger
- Usual EWC code
- 16 05 06*
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
Legacy pigment usually turns up as a small jar of bright yellow powder at the back of a school or college prep room, and it may have drifted there from an art store. Wherever it came from, it belongs in a locked cabinet with a stock record, clear of food and drink areas, acids and oxidisers, because it combines lead and chromium(VI) and may cause cancer. Fine powder is the practical concern. It clings to threads and shoulders, so a jar that has been opened over the years can leave yellow dust where it stood. A tray of its own keeps any dust visible and contained. Leave the lid alone, since nobody needs to look inside to keep it properly, and keep the stock entry current so the jar does not become an unknown.
How to tell it has deteriorated
Labels and lids tell you more than the powder does here. Legacy jars often have a faded label, a cap stained yellow by the contents or a seal that has failed, and those are the things to note. Lead(II) chromate gives few visible signs of age, so a jar that looks unchanged after decades is no surprise, and it is no reassurance either, because the lead and chromium(VI) remain in the solid however old it is. Caking or an unexpected colour may only mean damp or contamination, though it still belongs in the record. Yellow dust on the shelf beneath a jar points to a failed seal, and it should be left undisturbed and mentioned when collection is arranged. A lost stock record is a common failing with this sort of stock.
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 specialist collection is how it leaves the site, with a registered waste carrier taking it to a permitted facility, and there is no other route. It must not go into a sink, drain, general waste bin or skip, and nobody should try to treat it first, given how toxic it is to aquatic life. Describe it as lead(II) chromate with the number of jars and approximate weight, because "yellow pigment" tells a carrier nothing about the lead or the chromium(VI). If a label reads only chrome yellow, pass that on as written. In the lab pack it travels among compatible toxic solids, clear of acids and oxidisers. A hazardous waste consignment note applies in England and Wales, or a special waste one in Scotland, and your copy stays on file afterwards.
| 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
- 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: legacy stock.
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
- H350 May cause cancer.
- 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.
Precautionary statements
- P203 Obtain, read and follow all safety instructions before use.
- P260 Do not breathe dust, fume, gas, mist, vapours or spray.
- P273 Avoid release to the environment.
- P280 Wear protective gloves, protective clothing, eye protection and face protection.
- P318 If exposed or concerned, get medical advice.
- P319 Get medical help if you feel unwell.
- P391 Collect spillage.
- 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 jar just says chrome yellow. Is that lead chromate?
Chrome yellow is the traditional pigment name for lead chromate, although pigment products can contain other ingredients. Describe it exactly as the label reads and say the make-up is uncertain. Until supplier information settles it, keep it as suspected lead and chromium(VI) stock, and do not test it yourself.
The jar has been sealed for decades. Is it still hazardous waste?
Yes. Time on the shelf removes neither the lead nor the chromium(VI), and the classification covers cancer, harm to the unborn child and organ damage through repeated exposure. A tight seal helps when it travels, so leave it closed and enter it on the stock record as it stands.
Can we rinse out an empty looking pigment jar and bin it?
No. Never rinse it into a sink or drain, because the compound is very toxic to aquatic life with long lasting effects. A jar that looks empty can still hold fine powder in the thread and shoulder, so keep it closed and include it in the collection list.
Where should it wait until the collection?
Locked in the toxic cabinet with a stock entry, on its own tray and away from acids and oxidisers. Move any jar found in an art store or open classroom cupboard to that cabinet only if its seal is sound, and record the move in the stock record.
