SECTION 7: Safe Work Practices and Procedures

7C: Peroxide Forming Compounds and Reactives

• Recommended Work Practices
• Examples of Peroxidizable Compounds
• Detection of Peroxides
• Removal of Peroxides
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  Certain chemicals can form dangerous peroxides on exposure to air and light. Since they are sometimes packaged in an atmosphere of air, peroxides can form even though the containers have not been opened. Peroxides may detonate with extreme violence when concentrated by evaporation or distillation, when combined with other compounds, or when disturbed by unusual heat, shock or friction. Formation of peroxides in ethers is accelerated in opened and partially emptied containers. Refrigeration will not prevent peroxide formation and stabilizers will only retard formation.

Peroxide formation may be detected by visual inspection for crystalline solids or viscous liquids, or by using chemical methods or specialized kits for quantitative or qualitative analysis. If you suspect that peroxides have formed, do not open the container to test since peroxides deposited on the threads of the cap could detonate.

See Anecdotes for an account of an incident in our laboratories involving peroxide detonation.

Recommended Work Practices (top)

• Know the properties and hazards of all chemicals you are using through adequate research and study, including reading the label and MSDS.
• Inventory all chemical storage at least twice a year to detect forgotten items, leaking containers, and those that need to be discarded.
• Identify chemicals that form peroxides or otherwise deteriorate or become more hazardous with age or exposure to air. Label containers with the date received, the date first opened and the date for disposal as recommended by the supplier.
• Minimize peroxide formation in ethers by storing in tightly sealed containers placed in a cool place in the absence of light. Do not store ethers at or below the temperature at which the peroxide freezes or the solution precipitates.
• Choose the size container that will ensure use of the entire contents within a short period of time.
• Visually or chemically check for peroxides of any opened containers before use.
• Clean up spills immediately. The safest method is to absorb the material onto vermiculite or a similar loose absorbent.
• When working with peroxidizable compounds, wear impact-resistant safety eyewear and face shields. Visitor specs are intended only for slight and brief exposure, and should not be used when working with peroxidizable compounds.
• Do not use solutions of peroxides in volatile solvents under conditions in which the solvent might be vaporized. This could increase the concentration of peroxide in the solution.
• Do not use metal spatulas or magnetic stirring bars (which may leach out iron) with peroxide forming compounds, since contamination with metals can lead to explosive decomposition. Ceramic, Teflon or wooden spatulas and stirring blades are usually safe to use.
• Do not use glass containers with screw-top lids or glass stoppers. Polyethylene bottles with screw-top lids may be used.

Examples of Peroxidizable Compounds (top)

* Under storage conditions in the liquid state the peroxide-forming potential increases and certain of these monomers (especially butadiene, chloroprene, and tetrafluoroethylene) should be discarded after three months.

Detection of Peroxides (top)

If there is any suspicion that peroxide is present, do not open the container or otherwise disturb the contents. Call EHS for disposal. The container and its contents must be handled with extreme care. If solids, especially crystals, for example, are observed either in the liquid or around the cap, peroxides are most likely present.

If no peroxide is suspected but the chemical is a peroxide former, the chemical can be tested by the lab to ensure no peroxide has formed.

• Peroxide test strips, which change color to indicate the presence of peroxides, may be purchased through most laboratory reagent distributors.  For proper testing, reference the manufacturer’s instruction.  Do not perform a peroxide test on outdated materials that potentially have dangerous levels of peroxide formation

Removal of Peroxides (top)

If peroxides are suspected, the safest route is to alert EHS for treatment and disposal of the material. Attempting to remove peroxides may be very dangerous under some conditions.

For more information:

• Chemical Incompatibility Chart
• Chemical Reactivity Worksheet - Excellent web-based database
• Chemical Reactivity Hazards - OSHA

Additional resources for chemicals that exhibit explosive properties, peroxide formation and container pressurization hazards.

Section 7D: Corrosives
Section 7B: Flammable Materials