Peroxide Forming Chemicals
Materials that are susceptible to peroxide formation (i.e.,
autooxidation) are ones that typically react with air, moisture or impurities
and produce a change in their chemical composition in normal storage.
The peroxides that form are less volatile than the solvent itself and
thus tend to concentrate. This is particularly dangerous if peroxides
are present during a distillation, where the applied heat to the concentrated
solution may trigger a violent explosion. Equally dangerous is to allow
a container of this material to evaporate to dryness, leaving the crystals
of peroxide at the bottom of the container.
Chemicals that are sensitive to peroxide formation can
be broken into three categories (Jackson, J. Chem. Ed., 1970)
as shown in the following table.

A. Peroxide hazard after prolonged storage. Form potentially explosive peroxides
without concentrating.
All have been responsible for fatalities.
Test for peroxide formation or discard after 3 months.
isopropyl ether divinyl acetylene
potassium metal potassium amide
sodium amide vinylidene chloride
B. Chemicals which become a peroxide hazard if concentrated, such as through
distillation or evaporation.
Test for peroxide formation or discard after 1 year.
dioxane diethyl ether
tetrahydrofuran acetal
cumene cyclohexane
cyclopentene diacetylene
dicyclopentadiene ethylene glycol dimethyl ether
furan methyl acetylene
methyl cyclopentane methyl-isobutyl ketone
tetrahydronaphthalene vinyl ethers
C. Chemicals which are a hazard due to peroxide initiation of polymerization.
The peroxide forming potential increases for liquids of this group.
Test for peroxide formation or discard after 1 year.
butadiene chlorobutadiene
chlorotrifluoroethylene styrene
tetrafluoroethylene vinyl acetate
vinyl acetylene vinyl chloride
vinyl pyridine acrylonitrile

The materials in group A are particularly hazardous and are capable of
forming peroxides that may explode even without undergoing distillation
or evaporation. One of the more dangerous is isopropyl ether, which decomposes
rapidly on storage so that crystals of peroxides accumulate in the threads
under the cap. This condition is extremely dangerous and the
container should not be opened - friction may initiate detonation. Materials
discovered in this condition may need to be removed by a bomb squad from
the local fire department. These chemicals should never be stored
for longer than 3 months; after this time they should be discarded without
opening or should be tested for peroxide formation. Any container that
has been stored for greater than 6 months should be approached with extreme
caution.
The chemicals in groups B and C should be discarded or tested for peroxide
formation after 12 months.
If the age of any of these compounds is unknown, or is suspected to be
greater than these recommended time frames, the container should not
be opened.
Detection of Peroxide Formation in Laboratory Chemicals
A simple qualitative test can be performed on peroxide forming compounds
to test for peroxide content. This test is based on the oxidation of iodide
ion to iodine and is accomplished by adding 1 mL of the substance to be
tested to a freshly prepared solution of 100 mg of sodium or potassium
iodide in 1 mL of glacial acetic acid. A yellow color indicates a low
concentration of peroxide in the sample; a brown color indicates a high
concentration. This test is sensitive to the formation of hydroperoxides
(ROOH), which is the principal hazard associated with peroxide-forming
solvents, but does not detect difficult to reduce peroxides such as dialkyl
peroxides (ROOR). This type of peroxide can be detected by a reagent consisting
of 3 g of sodium iodide dissolved in 50 mL of glacial acetic acid and
adding 2 mL of 37% hydrochloric acid.
More recently, test strips have been developed that will test for the
presence of peroxides in a much more straightforward fashion.
Precautions for Handling Peroxide Forming Materials
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