Explosive and detonable substances must be subject to a risk assessment before purchase to ensure that appropriate facilities for use and storage are available.
Peroxide-forming materials are chemicals that react with oxygen (including air), heat and light to form peroxides. Peroxides are very unstable, and some chemicals that can form explosive peroxides are commonly used in laboratories. This makes peroxide-forming materials some of the most hazardous substances found in a lab. The tendency to form peroxides by most of these materials is greatly increased by evaporation or distillation. Organic peroxides are extremely sensitive to shock, sparks, heat, friction, impact, and light. Many peroxides formed from materials used in laboratories are more shock sensitive than TNT. Just the friction from unscrewing the cap of a container of an ether that has peroxides in it can provide enough energy to cause a severe explosion.
Peroxide-forming compounds can be divided into three hazard categories: Storage times are based on time after opening container.
- Compounds forming peroxides that can spontaneously decompose during storage. Maximum storage time = 3 months.
- Compounds forming peroxides that require the addition of a certain amount of energy (distillation, shock) to explosively decompose. Maximum storage time = 12 months.
- Compounds that have the potential to form peroxide polymers, a highly dangerous form of peroxide which precipitate from solution easily and are extremely heat and shock-sensitive. Maximum storage time = 12 months.
Precautions / Storage
All containers of peroxidizable compounds should have a warning label indicating the date received and the date opened. The label should indicate that the material is to be tested or discarded within either 1, 3, or 6 months after opening.
Do not open any container which has obvious crystal formation around the lid.
All peroxidizable substances should be stored away from heat and light and be protected from ignition sources.
When it is necessary to test for the presence of peroxides: do not test the solution if it has been stored longer than two years. Do not test the solution if crystals are visible in the container or crystals are on or in the container. Do not test the solution if the container has a metal screw cap. If it is safe to test the solution, the presence of peroxides can be detected by mixing 1-3 ml of the liquid to be tested with an equal volume of acetic acid and then adding a few drops of a 5% potassium iodide solution. A yellow to brown colour indicates the presence of peroxides. Commercial test strips are also available.
Other precautions are similar to those used for flammable materials.