For a simple peroxide test soak filter paper stripes in KI / starch solution. Peroxides should give a purple-blueish spot due to the I2 / starch inclusion complex. But only ethers (especially diethylether) form explosive peroxides on storage under light and oxygen.
Is this KI/starch solution turning purple the same as the iodometric titration they use to determine the concentration of peracids in a solution? I have read about "iodometric titrations" in a couple of peracid-related articles, but they never explain how exactly they performed the titration.