Peroxide Formers

Peroxide Formers

Many laboratory chemicals are prone to the formation of explosive peroxides under normal usage. Opinions vary regarding the level at which peroxide formation poses a risk: while a maximum concentration of 100 ppm is widely accepted among industrial hygienists, OSHA has no published guidelines for the storage, use, and disposal of peroxidizable chemicals. To ensure the safety of Gettysburg College employees, the following guidelines have been established with regards to peroxide forming chemicals.

  1. Purchasing Guidelines
  2. Labeling Requirements
  3. Safe Handling
  4. Disposal
  5. Storage Guidelines
  6. Storage Limits
  7. Groups of Peroxide-Formers
  8. Testing Guidelines
  9. References
  1. Purchasing Guidelines

    Peroxidizable compounds should be purchased in quantities, which can be exhausted within the time indicated in Table A. Container sizes should be selected according to use requirements so that exposure to air is minimized through reduced container openings.

  2. Labeling Requirements

    All peroxidizable materials in Lists A - D must have a label containing the date received from the manufacturer and the date opened. Additionally, labels must state, “Peroxidizable Compound: Discard or Test Within # # Months After Opening,” where # # is the safe storage period from Table A. Labels should be in red print on a white background.

    Download a sheet of labels in DOC | PDF format.

  3. Safe Handling

    Test for peroxides before distilling or evaporating any List A or B material. Before distilling any List C material, a suitable polymerization inhibitor must be added. During distillation, addition of a high molecular weight inerting solvent, such as mineral oil or a phthalate ester will dilute residual peroxides when distillation is complete. Should such a dilutent be undesirable, distill to not less than 10%. NEVER distill to a dry residue.

    Use safety glasses and a face shield when evaporating or distilling mixtures that contain peroxidizable compounds.

  4. Disposal

    All peroxidizable compounds from Lists AóD will be removed from laboratories for disposal after the safe storage period expires. This includes unopened chemicals after 18 months of storage.

    All peroxidizable compounds suspected of having high peroxide levels, because of visual observation of unusual viscosity or crystal formation, or because of age, should be considered extremely dangerous. DO NOT attempt to open these containers as peroxide crystals around the container cap could detonate. Contact the Environmental Health & Safety Office at 337-6813 for assistance.

  5. Storage Guidelines

    All peroxidizable compounds should be stored away from heat and light. All containers must have tight closures to prevent air exposure, evaporation and concentration of peroxides.

  6. Storage Limits

    Opened Containers:

    DescriptionSafe Storage PeriodTesting Frequency
    Unopened Containers 18 months Annual
    Opened Containers
    Chemicals in list A 3 months 3 months
    Chemicals in List B and D 12 months Annual
    Uninhibited Chemicals in List C 24 hours DO NOT BUY
    Inhibited Chemicals in List C 12 months1 Annual

    1Do ont store inhibited peroxide-formers under inert atmosphere as oxygen is required for the inhibitor to function.

  7. Groups of Peroxide-Formers

    List A: Chemicals that form explosive peroxides without concentration

    • Butadiene (liquid monomer)
    • Chloroprene (liquid monomer)
    • Divinylacetylene
    • Isopropyl ether
    • Tetrafluoroethylene (liquid monomer)
    • Vinylidene chloride


    List B: Chemicals that form explosive peroxides on concentration

    • Acetal
    • Acetaldehyde
    • Benzyl alcohol
    • 2-Butanol
    • Cumene
    • Cyclohexanol
    • 2-Cyclohen-1-ol
    • Cyclohexene
    • Decahydronaphthalene
    • Diacetylene
    • Dicyclopentadiene
    • Diethyl ether
    • Diethlene glycol dimethyl ether (diglyme)
    • Dioxanes
    • Ethylene glycol dimethyl ether (glyme)
    • 4-Heptanol
    • 2-Hexanol
    • Methylacetylene
    • 3-Methyl-1-butanol
    • Methylcyclopentane
    • Methyl isobutyl ketone
    • 4-Methyl-2-pentanol
    • 2-Penten-1-ol
    • 4-Penten-1-ol
    • 1-Phenylethanol
    • 2-Phenylethanol
    • Tetrahydrofuran
    • Vinyl ethers
    • Other Secondary Alcohols

    List C: Chemicals that may autopolymerize as a result of peroxide accumulation

    • Acrylic acid2
    • Acrylonitrile2
    • Butadiene
    • Chloroprene
    • Chlorotrifluoroethylene
    • Methyl methacrylate2
    • Styrene
    • Tetrafluoroethylene
    • Vinyl acetate
    • Vinylacetylene
    • Vinyl chloride
    • Cinylpyridine
    • Vinyladiene chloride

    2Although these chemicals form peroxides, there have be no reported explosions.

    List D: Chemicals that may form peroxides but cannot clearly be placed in List A-C

    • Acrolein
    • Allyl ether 3
    • Allyl ethyl ether
    • Allyl phenyl ether
    • p-(n-Amyloxyl)benzoyl chloride
    • n-Amyl ether
    • Benzyl n-butyl ether
    • Bethzyl ether
    • Benzyl ethyl ether
    • Benzyl methyl ether
    • Benzyl 1-naphthalene ether3
    • 1,2-Bis(2-chloroethoxy)ethane
    • Bis(2-ethxoyethyl) ether
    • Bis(2-methoxyethoxy)ethyl) ether
    • Bis(2-chloroethyl) ether
    • Bis(2-ethoxyethyl) adipate
    • Bis(2-ethoxyethyl) phthalate
    • Bis(2-methoxyethyl) carbonate
    • Bis(2-methoxyethyl) ether
    • Bis(2-methoxyethyl) phthalate
    • Bis(2-methoxymethyl) adipate
    • Bis(2-n-butoxyethyl) phthalate
    • Bis(2-phenoxyethyl) ether
    • Bis(4-chlorobutyl) ether
    • Bis(chloromethyl) ether
    • 2-bromomethyl ethyl ether
    • Bromophenetole
    • 3-bromopropyl phenyl ether
    • 1,3-butadiyne
    • Buten-3-yne
    • Tert-butyl ethyl ether
    • Tert-butyl methyl ether
    • n-butyl phenyl ether
    • n-butyl vinyl ether
    • Chloroacetaldehyde diethylacetal3
    • 2-chlorobutadiene
    • 1-(2-chloroethoxy)-2-phenoxyethane
    • Chloroethylene
    • Chloromethyl methyl ether
    • Chlorophenetole
    • Cyclooctene3
    • Cylcopropyl methyl ether
    • Diallyl ether3
    • p-Di-n-butoxybenzene
    • 1,2-dibenzyloxyethane3
    • p-Dibenzyloxybenze3
    • 1,2-dichloroethyl ethyl ether
    • 2,4-dichlorophenetole
    • Diethoxymethane3
    • 2,2-Diethoxypropane
    • Diethylethoxymethylenemalonate
    • Diethyl fumarate
    • Diethyl acetal3
    • Diethylketene
    • Diethoxybenzene
    • 1,2-Diethoxyethane
    • Dimethoxymethane3
    • 1,1-Dimethoxyethane3
    • Dimethylketene
    • 3,3-Dimethoxypropene
    • 2,4-Dinitrophenetole
    • 1,3-Dioxepane3
    • Di(1-propynyl) ether
    • Di(2-propynyl) ether
    • Di-n-propoxymethane3
    • 1,2-Epoxy-3-isopropoxypropane3
    • 1,2-Epoxy-3-phenoxypropane
    • Ethoxyacetophenone
    • 1-(2-Ethoxyethoxy)ethyl acetate
    • 2-Ethoxyethyl acetate
    • (2-ethoxyethyl)-o-benzoylbenzoate
    • 1-Ethoxynaphthalene
    • Ethoxyphenyl isocyanate
    • 1-ethoxy-2-propyne
    • 3-ethoxyopropionitrile
    • 2-ethylacrylaldehyde oxime
    • 2-ethylbutanol
    • Ethyl ethoxypropionate
    • 2-ethyl hexanal
    • Ethyl vinyl ether
    • Furan p-phenylphenetone
    • 2,5-hexadiyn-1-ol
    • 4,5-hexadien-2-yn-1-ol
    • n-hexyl ether
    • Iodophenetole
    • Isoamyl ether3
    • Isobutyl vinyl ether
    • Isophorone3
    • p-isopropoxypropionitrile3
    • Isopropyl 2,4,5-trichlorophenoxyacetate
    • Limonene
    • 1,5-p-methadiene
    • Methyl p-(n-amyloxy)benzoate
    • 4-methyl-2-pentanone
    • n-methylphenetole
    • 2-methyltetrahydrofuran
    • 3-methoxy-1-butyl acetate
    • 2-methoxyethanol
    • 3-methoxyethyl acetate
    • 2-methoxyethyl vinyl ether
    • Methoxy-1,3,5,7-cyclooctatetraene
    • Methoxypropionitrile
    • m-Nitrophenentole
    • 1-Octene
    • Oxybis(2-ethyl acetate)
    • Oxybis(2-ethyl benzoate)
    • Oxydipropionitrile
    • 1-Pentene
    • Phenoxyacetyl chloride
    • Phenoxypropionyl chloride
    • Phenyl o-propyl ether
    • n-propyl ether
    • n-propyl isopropyl ether
    • Sodium 8,11,14-eicosatetraenoate
    • Sodium ethoxyacetylide
    • Tetrahydropyran
    • Triethylene glycol diacetate/li>
    • Triethylene glycol diproprionate
    • 1,3,3-trimethoxypropene3
    • 1,1,2,3-tetrachloro-1,3-butadiene
    • 4-vinyl cyclohexene
    • Vinylenecarbonate
    • Vinylidene chloride3

    3These chemicals easily form peroxides and should probably be considered under List B

  8. Testing Guidelines

    All peroxide-forming chemicals shall be tested at least annually. When the peroxide concentration exceeds 100ppm, the container shall be properly disposed at the earliest convenience.

    To assist in this process, the CisPro inventory system allows us to track peroxide formers throughout the departments. This is one of many reasons that maintaining a proper inventory is imperative to the safe operation of science labs on-campus.

    Detection and Inhibition of Peroxides: Basic Protocols

    Ferrous Thiocyanate Detection Method

    Ferrous thiocyanate will detect hydroperoxides with the following test:

    • Mix a solution of 5mL 1% ferrous ammonium sulfate, 0.5mL 1M sulfuric acid and 0.5mL 1M ammonium thiocyanate (if necessary decolorize with a trace of zinc dust).
    • Shake with an equal quantity of the solvent to be tested.
    • If peroxides are present, a red color will develop.

    Potassium Iodide Detection Method

    • Add 1mL freshly prepared 10% solution of potassium iodide to 10mL of ethyl ether in a 25mL glass-stoppered cylinder of colorless glass protected from light (both components are clear).
    • A resulting yellow color indicates the presence of 0.005% peroxides.

    Inhibition of Peroxides

    • Storage and handling under an inert atmosphere is a useful precaution.
    • Addition of 0.001% hydroquinone, diphenylamine, polyhydroxyphenols, aminophenols or arylamines may stabilize ethers and inhibit formation of peroxides.
    • Dowex-1® has been reported effective for inhibiting peroxide formation in ethyl ether.
    • Hydroquinone effective for peroxide inhibition in tetrahydrofuran.
    • Stannous chloride or ferrous sulfate effective for peroxide inhibition in dioxane.

    Peroxide Test Strips

    These test strips are available from EM Scientific, cat. No. 10011-1 or from Lab Safety Supply, cat. No. 1162. These strips quantify peroxides up to a concentration of 25ppm. Aldrich Chemical has a peroxide test strip, cat. No. Z10,168-0, which measures up to 100ppm peroxide. The actual concentration at which peroxides become hazardous is not specifically stated in the literature. A number of publications use 100ppm as a control value for managing the material safely.

  1. References
    • Recognition and Handling of Peroxidizable Compounds; Data Sheet 655; National Safety Council: Chicago, IL, 1987
    • Kelly, Richard J., Review of Safety Guidelines for Peroxidizable Organic Chemicals, Chemical Health & Safety, American Chemical Society, Sept/Oct. 1996
    • Furr, Keith Handbook of Lab Safety, 4th ed., CRC Press, 1995.