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

Alizarin red S (CAS 130-22-3): storage and disposal

Alizarin red S is the orange-brown dye that binds calcium and turns bone and mineralised tissue red, so it features in histology, pathology and university teaching of skeletons as well as in some school and college stores. The recorded hazards are skin irritation, serious eye irritation and respiratory irritation. It is a fine powder, and it stains accordingly.

CAS number
130-22-3
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 it in a closed bottle on a general shelf below eye level, as dust is the irritant route, and in a tray so that orange powder does not stain the shelf. Because it is used to find calcium, keep it away from calcium salts such as chalk or calcium carbonate stock, which would leave coloured marks if they leak onto it. In a histology lab it sits with the other stains. In a school or university teaching store, bone staining kits may carry it, so check the box label too. Date the bottle on opening, and keep it away from food supplies and from acid and alkali bottles.

How to tell it has deteriorated

Orange to brownish is the normal powder, so staining is the normal sign of use. A technician sees orange or red marks on the cap, label and shelf first. The chemical-specific point is that the dye binds calcium and shifts colour with acid and alkali, so a stock solution that has changed from its supplied colour has probably met one of these. Caked or damp powder shows moisture has entered, and a dried dye ring and a crust round the thread show where drips escaped. Dust on the shelf matters because it is 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. The code in a research or school lab is 16 05 06*, a pathology, histology or human healthcare setting uses 18 01 06*, and 16 05 08* applies to a discarded organic chemical outside a lab pack. Record whether it is powder or solution, the amount and the room. Stained specimens and tissue follow your biological route and not this one. Bottles go into a lab pack with compatible items. A sink or drain is not an acceptable route, and nobody should try to bleach the stain.

Waste codes and transport details for Alizarin red S
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, bone staining.

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 alizarin red S?

Skin irritation, serious eye irritation and respiratory irritation. The fine powder is the main concern, so keep the bottle closed, below eye level and do not sweep spilt dust dry.

Do stained bone specimens go in the chemical collection?

No. Specimens and tissue follow your biological or clinical waste route. The dry dye and any stain solution are the chemical items for specialist collection, listed separately.

Why has our alizarin red S solution changed colour?

The dye shifts colour with acid and alkali and binds calcium, so a change from the supplied colour suggests contamination. Take the bottle out of use 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 C14H7NaO7S. EC number 204-981-8.

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