These are effective until the container is first opened. After a container is opened, the chemical comes in contact with air and may begin to form peroxides. Therefore, there are two steps to prevent the hazards of peroxide formation. The first step in preventing the formation of peroxides is to date all containers of peroxide forming chemicals with the date the container was first opened. The second step is to dispose of the peroxide forming chemicals within six months of the date the container was first opened.
Manufacturers often state warnings on their peroxide forming chemicals.
Ethers Vinyl Pyridine Vinylidene Chloride Vinylidene Dichloride 2. Picric Acid and other Polynitroaromatic Compounds Picric Acid is commonly used in labs and is relatively safe in the form which it is sold. However, picric acid can become explosive when it is allowed to dry out or when it forms certain metal salts. Check Picric Acid frequently to ensure it remains damp. Add water if needed.