You should routinely test ethers and other peroxide-forming solvents prior to distillation.

Peroxide Test Strips

Commercial test strips are available from Sigma-Aldrich Chemical Company (Quantofix® Test Sticks for Peroxides, catalog #37206). These strips are convenient to use; however, they do not have the universality or the sensitivity of the ferrous thiocyanate test, and have a limited shelf life.

Figure 13.2
Quantofix® peroxide test sticks. These strips are colorimetric, and can detect peroxides at a range of 1-100 mg/L.

Ferrous Thiocyanate Test

Mix a fresh solution in the following proportions:

  • 5 units of 1% ferrous ammonium sulfate [(NH4)2Fe(SO4)2] in water
  • 0.5 units of 1N sulfuric acid (H2SO4)
  • 0.5 units of 0.1 molar ammonium thiocyanate (NH4SCN); to make a 0.1M solution, dissolve 7.16 grams in 1L of distilled water
  • Decolorize with a trace of zinc dust if necessary

Shake an equal quantity (six units) of the solvent to test with the above reagent. Appendix 13-A, Table III shows the relation between color change and peroxide content.