The University of Iowa

SAFETYmatters - Peroxide Formers Reminder

The last year has disrupted many activities in the labs. One item that might have been overlooked is the testing of peroxide formers. Over time, these chemicals can form crystals that may explode from impact, heat, or friction. Some may become hazardous even if never opened. Please double-check that your peroxide forming chemicals have been checked for degradation and/or tested recently.

Different peroxide formers degrade under different conditions and over different timespans. Many times, the manufacturer will print an expiration date on the container.

For liquids:

  • Date containers when first opened.
  • A septum or sure-seal is no guarantee against peroxide-formation. The contents of these containers should also be tested.
  • Do not open any container with evidence of crystal formation around the lid or in the liquid.
  • Use peroxide test strips to test the liquid for peroxide formation. Record the test date and results on the container.
  • Containers must be disposed of before reaching 25 ppm peroxide. For containers above 25 ppm, see Disposal Procedure for Improperly Managed Peroxide-Forming Chemicals.
  • Examples of common liquid peroxide formers: ethyl ether, tetrahydrofuran, and 1,4-dioxane

For solids:

  • Look for discoloration and/or formation of a surface crust (for example, potassium metal forms a yellow or orange superoxide at the surface).
  • Dispose of the container by the manufacturer-issued expiration date.
  • Contact EHS with any questions regarding the disposal of suspect solid peroxide formers.
  • Examples of common solid peroxide formers: sodium or potassium metals, benzoyl peroxide, and sodium or potassium amide.

Do not move or disturb any container if there is any question regarding the presence of peroxides. In such cases, avoid additional testing or handling and immediately contact Jim Pyrz at 335-4625 or Rick Byrum at 335-9379.

More information about peroxide forming chemicals is available on our website on the Peroxide-Formers page. This page provides a list of peroxide formers and the recommended timetable for their testing.