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

tert-Butyl hydroperoxide (CAS 75-91-2): storage and disposal

tert-Butyl hydroperoxide is an organic peroxide reagent held in university research labs, typically as a solution of about 70%. It is flammable, causes severe burns, is toxic through the skin and is suspected of causing genetic defects. It also decomposes in storage and builds pressure, faster with heat or contamination. How old the bottle is, how it looks and how much pressure might be inside decide what can be done with it.

CAS number
75-91-2
Form
Solution
Storage class
Oxidiser
Signal word
Danger
Usual EWC code, laboratory stock
16 05 06*
  • Flammable pictogramFlammable
  • Corrosive pictogramCorrosive
  • Acute toxicity pictogramAcute toxicity
  • Serious health hazard pictogramSerious health hazard
  • Hazardous to the environment pictogramHazardous to the environment

This chemical is a manual enquiry

This can become unstable or explosive, especially if it is old or has dried out. Nobody should move it until someone competent has looked at it, so we start with a conversation and usually a store assessment.

Organic peroxide: heat and shock sensitive.

It cannot be priced through a form. Please do not open or move it. Call us or send an enquiry and we will talk through the next step, which depends on what it is. Keep following your own procedures for controlled drugs, radioactive materials, gases and asbestos.

What to do this week

  1. Leave it where it is. If it looks old, crystalline or damaged, do not open or move it and keep people away from the shelf. If there is immediate danger, such as a leak, fumes or a fire, leave the area and call 999.
  2. Write down the label wording, the rough age and where it is stored, from a safe distance.
  3. Send us those details, and a photo if you can take one without touching it.

Safe storage in a school or lab

The usual stock is a supplier's bottle of the solution at about 70%, often sitting among research reagents long after the project that used it has finished. List it on its own in your records, and if it is old, leave it physically where it stands. Fresh stock wants a separate oxidiser space, cool and shaded, away from flammable solvents, organic materials, acids, alkalis and anything toxic that could react. Traces of metal and rust speed up its decomposition, so metal shelves and shared metal tools near the bottle are a poor idea. Where the supplier requires refrigeration, it must be a spark-free unit. Leave enough space around the bottle that a failed closure would not contaminate its neighbours.

How to tell it has deteriorated

Ageing here is a matter of slow decomposition, with gas building up inside a sealed bottle. The solution itself usually stays clear and pale, so it gives few visual signs and its appearance is no proof of safety. What you can see is the container: a bulging or domed cap, a distorted plastic bottle, a wet or crusted neck, or a stain on the shelf. A cap that has corroded points to fumes escaping. Unexpected colour or cloudiness suggests contamination. Old stock is the concern because nobody can tell what pressure has built up. If it is old, undated or shows any of these signs, do not move it, do not open it, and get a specialist assessment. Loosening a cap to relieve pressure is never acceptable.

Decomposes on storage and builds pressure.

How it is disposed of

This does not go through our standard collection route. It is arranged by manual enquiry, and never goes down the drain or into general waste.

Grouping is the sticking point. An organic peroxide that is flammable, corrosive and able to feed a fire does not fit easily into any ordinary lab pack group, which is why it goes by manual enquiry and is not quoted online. A store assessment is recommended, and a competent chemist needs to see the bottle in person, or an explosives or emergency specialist if warning signs are present. Give the concentration as printed on the label, the volume left, the date the bottle was opened, and the solvent if known. Mention any metal contact too. It is toxic to aquatic life and must not reach a drain, and nobody should attempt to quench or dilute it while awaiting advice.

Waste codes for tert-Butyl hydroperoxide
Usual EWC code, laboratory stock16 05 06*
Discarded organic chemical, not a laboratory pack16 05 08*
Usually classed as hazardous wasteYes

The code depends on where the waste came from and what it contains, and classifying it is the producer's duty. Use the waste code finder to see why.

Do not store with

  • FlammableOxidisers can ignite flammable materials or make a fire far more intense.
  • AcidMany oxidisers release toxic gas or become unstable in contact with acid.
  • AlkaliSome oxidisers react strongly with alkalis, and ammonia based stock is especially at risk.
  • ToxicToxic and oxidising stock are stored apart. A reaction could release toxic vapours.
  • CorrosiveCorrosive stock can react with oxidisers, releasing heat or fumes.

Named chemicals to keep apart

  • Acetic acidMany oxidisers release toxic gas or become unstable in contact with acid.
  • AcetoneOxidisers can ignite flammable materials or make a fire far more intense.
  • Ammonia solutionSome oxidisers react strongly with alkalis, and ammonia based stock is especially at risk.
  • EthanolOxidisers can ignite flammable materials or make a fire far more intense.
  • FormalinToxic and oxidising stock are stored apart. A reaction could release toxic vapours.
  • HexaneOxidisers can ignite flammable materials or make a fire far more intense.
  • Hydrochloric acidMany oxidisers release toxic gas or become unstable in contact with acid.
  • Mercury(II) chlorideToxic and oxidising stock are stored apart. A reaction could release toxic vapours.
Show 9 more
  • MethanolOxidisers can ignite flammable materials or make a fire far more intense.
  • Nitric acidMany oxidisers release toxic gas or become unstable in contact with acid.
  • Potassium hydroxideSome oxidisers react strongly with alkalis, and ammonia based stock is especially at risk.
  • Sodium cyanideToxic and oxidising stock are stored apart. A reaction could release toxic vapours.
  • Sodium hydroxideSome oxidisers react strongly with alkalis, and ammonia based stock is especially at risk.
  • Sulfuric acidMany oxidisers release toxic gas or become unstable in contact with acid.
  • Thionyl chlorideCorrosive stock can react with oxidisers, releasing heat or fumes.
  • TolueneOxidisers can ignite flammable materials or make a fire far more intense.
  • Zinc chlorideCorrosive stock can react with oxidisers, releasing heat or fumes.

Common quantities

Usually held as: about 70%.

Tell us the container size and how many you hold. An estimate is enough to start with, and some items cannot be priced until someone has looked at them.

Where it is commonly held

Hazard statements

  • H226 Flammable liquid and vapour.
  • H242 Heating may cause a fire.
  • H302 Harmful if swallowed.
  • H311 Toxic in contact with skin.
  • H314 Causes severe skin burns and eye damage.
  • H317 May cause an allergic skin reaction.
  • H332 Harmful if inhaled.
  • H341 Suspected of causing genetic defects.
  • H411 Toxic to aquatic life with long lasting effects.
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.
  • P210 Keep away from heat, hot surfaces, sparks, open flames and other ignition sources. No smoking.
  • P233 Keep container tightly closed.
  • P234 Keep only in original packaging.
  • P235 Keep cool.
  • P240 Ground and bond container and receiving equipment.
  • P241 Use explosion-proof electrical, ventilating and lighting equipment.
  • P242 Use non-sparking tools.
  • P243 Take action to prevent static discharges.
  • P260 Do not breathe dust, fume, gas, mist, vapours or spray.
  • P261 Avoid breathing dust, fume, gas, mist, vapours or spray.
  • P262 Do not get in eyes, on skin, or on clothing.
  • P264 Wash hands and exposed skin thoroughly after handling.
  • P264+P265 Wash hands and exposed skin thoroughly after handling. Do not touch eyes.
  • P270 Do not eat, drink or smoke when using this product.
  • P271 Use only outdoors or in a well-ventilated area.
  • P272 Contaminated work clothing should not be allowed out of the workplace.
  • P273 Avoid release to the environment.
  • P284 In case of inadequate ventilation wear respiratory protection.
  • P301+P316 IF SWALLOWED: Get emergency medical help immediately.
  • P301+P317 IF SWALLOWED: Get medical help.
  • P301+P330+P331 IF SWALLOWED: Rinse mouth. Do NOT induce vomiting.
  • P302+P352 IF ON SKIN: Wash with plenty of water.
  • P302+P361+P354 IF ON SKIN: Take off immediately all contaminated clothing. Immediately rinse with water for several minutes.
  • P303+P361+P353 IF ON SKIN (or hair): Take off immediately all contaminated clothing. Rinse skin with water or shower.
  • P304+P340 IF INHALED: Remove person to fresh air and keep comfortable for breathing.
  • P305+P354+P338 IF IN EYES: Immediately rinse with water for several minutes. Remove contact lenses, if present and easy to do. Continue rinsing.
  • P316 Get emergency medical help immediately.
  • P317 Get medical help.
  • P319 Get medical help if you feel unwell.
  • P320 Specific treatment is urgent (see supplemental first aid instruction on this label).
  • P321 Specific treatment (see supplemental first aid instruction on this label).
  • P330 Rinse mouth.
  • P333+P317 If skin irritation or rash occurs: Get medical help.
  • P361+P364 Take off immediately all contaminated clothing. And wash it before reuse.
  • P362+P364 Take off contaminated clothing. And wash it before reuse.
  • P363 Wash contaminated clothing before reuse.
  • P370+P378 In case of fire: Use suitable extinguishing media to extinguish.
  • P391 Collect spillage.
  • P403 Store in a well-ventilated place.
  • P403+P233 Store in a well-ventilated place. Keep container tightly closed.
  • P403+P235 Store in a well-ventilated place. Keep cool.
  • P410 Protect from sunlight.
  • P411 Store at temperatures as specified on the label.
  • P420 Store separately.

Substance as classified, dilutions may differ.

Questions

A research group has left a half used bottle behind. Can we use it up?

Not if its age and history are unknown, as contamination during earlier use may have started decomposition. Record who used it and when, keep it in its present position, and raise an enquiry. Anything clearly old should stay untouched until someone competent has seen it.

Is a plastic bottle safer than glass for this reagent?

Neither container makes old stock safe, and the original supplier's packaging should not be swapped. A plastic bottle can show pressure through distortion, while glass may not show it at all. Report what the bottle is made of in your enquiry, without handling it to find out.

How do we spot a contamination problem before anything visibly happens?

Mostly through records rather than appearance. Note who has taken samples from the bottle and whether metal tools or shared funnels were used. If that history is missing, assume contamination is possible. An assessor can then decide how the bottle should be treated.

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 C4H10O2. EC number 200-915-7.

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