Phenolphthalein (CAS 77-09-8): storage and disposal
Phenolphthalein is the classic acid-base indicator in school and college titrations, held as a white powder and as a 1% solution in ethanol. The recorded hazards are H350, which says it may cause cancer, together with H341, suspected of causing genetic defects, and H361f, suspected of damaging fertility. Many science departments still hold an old bottle, and the carcinogen statement is what decides how it is handled.
- CAS number
- 77-09-8
- Form
- Solid
- Storage class
- Toxic
- Signal word
- Danger
- Usual EWC code
- 16 05 06*
Serious health hazard
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
On a school prep room shelf the powder often sits beside the other indicators, which are a casual group of small bottles, and this one should be moved out of that group into a locked or restricted cupboard with a stock record. Keep it away from food areas, acids and oxidising agents. The 1% ethanol solution is a separate item that carries its own transport entry, UN 1993 on record, and should stand upright in a tray with the cap tight, away from heat and ignition sources. Date both powder and solution. A dropper bottle left on a trolley or bench is the most common storage fault.
How to tell it has deteriorated
White to pale yellowish is the normal powder, and the solution is colourless. A pink tint in the solution bottle is the one chemical sign worth noticing, as it suggests alkali has reached it, for instance from a contaminated dropper, and it may show in old glass bottles. The ethanol solvent escapes through a poor cap, so a bottle may be low and show white crystals around the thread where the indicator has dried out. Powder that is damp, clumped or stained brown by age should be recorded. Dust round the cap matters more than usual given the carcinogen statement.
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.
The usual code is 16 05 06*, with 16 05 08* used where it is a discarded organic chemical outside a lab pack. Record the powder and the ethanol solution as separate items, with strength, volume and the UN number 1993 where it is on the label for the solution. Solid bottles go into a lab pack with compatible solids, and the solution bottles go upright into the liquids part of a pack. A school science department should tell the collector how old the stock is. Phenolphthalein must never be washed to a sink or drain, and the H350 statement should be on the record.
| EWC code, laboratory chemicals | 16 05 06* |
|---|---|
| Discarded organic chemical, not a laboratory pack | 16 05 08* |
| 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: solid, 1% solution in ethanol.
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
- H341 Suspected of causing genetic defects.
- H350 May cause cancer.
- H361f Suspected of damaging fertility.
Precautionary statements
- P203 Obtain, read and follow all safety instructions before use.
- P280 Wear protective gloves, protective clothing, eye protection and face protection.
- P318 If exposed or concerned, get medical advice.
- 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 phenolphthalein stored in a restricted cupboard?
It carries H350, may cause cancer, along with H341 and H361f. A restricted cupboard with a stock record keeps it out of the casual indicator group and away from food areas, acids and oxidising agents.
Our phenolphthalein solution has a pink tinge. Is that a problem?
A pink tint in the bottle suggests alkali has reached the solution, so it is contaminated and no longer reliable as an indicator. Record it for collection and do not top up from other bottles.
Does the ethanol solution go in the same pack as the powder?
No. They are recorded as separate items. The solution carries UN 1993 on record and goes upright into the liquids part of the lab pack, while the powder goes with compatible solids.
