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Chemical collection and stock control for UK schools, universities and hospitals

Bromocresol purple (CAS 115-40-2): storage and disposal

Bromocresol purple is an indicator dye that is yellow in acid and purple in alkali, used in teaching labs and in microbiology media where bacteria change the colour as they ferment sugars. Stock is held as powder and as solution. The recorded hazards are skin irritation, serious eye irritation and respiratory irritation, and the fine powder is what makes it worth handling carefully.

CAS number
115-40-2
Form
Solid
Storage class
General
Signal word
Warning
Usual EWC code
16 05 06*
  • Harmful or irritant pictogramHarmful or irritant

What to do this week

  1. Check the label is readable and write down the opened date if it is not already there.
  2. Check it is stored as general stock and apart from the items listed under "Do not store with".
  3. 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

Keep this one away from acids and alkalis, because their drips alter the colour of the stock and the powder is an irritant that spreads easily. A closed bottle on a general shelf is the usual place, with dropper bottles upright in a tray, and in a pathology or microbiology store it sits with the other reagents for culture identification. Do not keep it above eye level, since dust and splashes reach the eyes. Label the solution with the opening date and keep it away from food supplies. Dye stock that is shared between a teaching lab and a clinical bench should be labelled so it does not travel between them unnoticed.

How to tell it has deteriorated

Check the cap and the label first. Purple or yellow staining on the cap, thread and shelf below shows drips have escaped, and the print on the label often smudges where they run. Inside, the solution may be lower than it was because of a loose cap, with a dried ring of dye round the neck. A solution that has changed from its supplied colour has probably met acid or alkali, perhaps from a contaminated dropper. Powder should be loose and fine, so damp or caked powder points to moisture. Dust round the cap matters for an irritant, so do not sweep it dry.

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.

With skin, eye and respiratory irritation on record, the dye is collected as hazardous waste. A research or teaching lab uses 16 05 06*, a human healthcare setting such as a pathology lab uses 18 01 06*, and 16 05 08* applies where it is a discarded organic chemical outside a lab pack. Say which fits and list powder and solution separately, with the strength, volume and room. Bottles go upright into a lab pack with compatible organic items. The dye is never washed to a sink or drain, however faint the colour, and nobody should try to bleach it away first.

Waste codes and transport details for Bromocresol purple
EWC code, laboratory chemicals16 05 06*
Discarded organic chemical, not a laboratory pack16 05 08*
Human healthcare setting18 01 06*
Hazardous wasteYes

The code depends on where the waste came from and what it is mixed with. Use the waste code finder to see why.

Common quantities we collect

Usually held as: solid, solution.

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

  • H315 Causes skin irritation.
  • H319 Causes serious eye irritation.
  • H335 May cause respiratory irritation.
Precautionary statements
  • P261 Avoid breathing dust, fume, gas, mist, vapours or spray.
  • P264 Wash hands and exposed skin thoroughly after handling.
  • P264+P265 Wash hands and exposed skin thoroughly after handling. Do not touch eyes.
  • P271 Use only outdoors or in a well-ventilated area.
  • P280 Wear protective gloves, protective clothing, eye protection and face protection.
  • P302+P352 IF ON SKIN: Wash with plenty of water.
  • P304+P340 IF INHALED: Remove person to fresh air and keep comfortable for breathing.
  • P305+P351+P338 IF IN EYES: Rinse cautiously with water for several minutes. Remove contact lenses, if present and easy to do. Continue rinsing.
  • P319 Get medical help if you feel unwell.
  • P321 Specific treatment (see supplemental first aid instruction on this label).
  • P332+P317 If skin irritation occurs: Get medical help.
  • P337+P317 If eye irritation persists: Get medical help.
  • P362+P364 Take off contaminated clothing. And wash it 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

What hazards are recorded for bromocresol purple?

Skin irritation, serious eye irritation and respiratory irritation. They are why the powder is kept low, in a closed bottle, and why spills of dust should not be swept dry.

Which waste code do we use in a pathology lab?

A human healthcare setting uses 18 01 06*, while a teaching or research lab normally uses 16 05 06*. Tell the collector which room the stock came from and they will confirm the code on the note.

Our bromocresol purple solution has turned a different colour. Is it spoiled?

A change from the supplied colour suggests contamination with acid or alkali, so it is no longer a reliable stock. Take it out of use, keep the cap on and record it for collection.

Guidance only. Check your own risk assessment and your supplier's safety data sheet.

Hazard data source: PubChem GHS Classification, retrieved 31 Oct 2026. Formula C21H16Br2O5S. EC number 204-087-8.

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