Chemical Instability

Stability refers to the susceptibility of the chemical to dangerous decomposition. Ethers, liquid paraffins, and olefins from unstable peroxides on exposure to air and light. Since these chemicals are packaged in an air atmosphere, peroxides can form even though the containers have not been opened.

A number of deaths have occurred when researchers have attempted to open containers of old, outdated peroxide-forming chemicals. In these cases, peroxide sensitive crystals formed around the cap, the friction generated by turning the cap caused the shock-sensitive crystals to react, acting as a primer, and ignited the contents of the container, resulting in an explosion. Organic peroxides and peroxide-forming chemicals are considered among the most hazardous substances handled in labs because they are very unstable, flammable, and extremely sensitive to friction, impact, and heat.

The label and SDS will indicate if a chemical is unstable. Purchase only what will be used in a short time and in the smallest size of container that is practical.

Date containers upon receiving and again upon opening.

Unless an inhibitor was added by the manufacturer, closed containers of ethers should be discarded after one (1) year or the manufacturer’s expiration date (whichever comes first). Open containers of ethers should be discarded within six (6) months of opening. Do not open out-of-date containers, particularly if various liquids or crystalline solids are observed in liquid peroxide-forming chemicals. Write the date received on the container. Write the date container is opened on the label

Store flammable chemicals in a properly grounded flammable storage cabinet located in a cool dry place away from direct sunlight. Purchase peroxide forming chemicals in metal containers. Although less preferable, amber bottles are also acceptable. Cap containers tightly to minimize peroxide formation. KEEP BOTTLES AND CAPS FREE OF CHEMICAL RESIDUE. Do not store diethyl ether in refrigerators. Chill ether in ice bath if chilling is required.

Handle peroxide-forming compounds in a laboratory hood. The immediate area must be free of ignition sources such as Bunsen burners and electrical equipment. Wear protective eyewear, gloves and laboratory coat when handling shock-sensitive compounds.

Never distill ethers unless they are known to be free of peroxides. Do not distill to dryness. Leave at least 10 percent at the bottom as most accidents involve a nearly dry residue.

Be careful with potassium and sodium. Peroxides are often present in the crust (used to prevent contact with air) around a chunk of potassium and sodium. When cut with a knife, the peroxide rapidly oxidizes the residual kerosene and can result in a fire or explosion.

Carefully handle near-empty and empty containers as an air space above the liquid accelerates the formation of peroxides.



Maximum Storage Time Periods for Peroxide-Forming Compounds

Three Months:

Divinyl acetylene Sodium amide
Isopropyl ether Potassium metal
Vinylidene chloride

Twelve Months:

Acetal 2-Hexanol
Acetaldehyde Methyl Acetylene
Benzyl Alcohol 3-Methyl-1-butanol
2-Butanol Dioxanes Methyl-isobutylketone
Butadiene 3-Methy-2-pentanol
Chlorofluoroethylene 2-Pentanol
Chlorobutadiene (Chloroprene) 4-Penten-1-ol
Chlorotrifluoroethylene 1-Phenylethanol
Cumene (isopropylbenzene) sec. Alcohols
Cyclohexene Styrene
2-Cyclohexen-1-ol Tetrafluoroethylene
Cyclopentene Tetrahydrofuran
Decahydronapthalene (decalin) Tetrahydronnapthalene
Diacetylene (butadiyne) Vinyl acetate
Dicyclopentadiene Vinyl acetylene
Diethyl ether Vinyl chloride
Diglyme Vinyl ether
Dioxane Vinyl ethyl ether
Ethylene glycol dimethyl ether Vinyl isobutyl ether
Furan Vinyl methyl ether
4-Heptanol Vinyl pyridine