Peroxide-Forming Chemicals

Overview

Peroxide-forming chemicals are a class of compounds that have the ability to form shock-sensitive explosive peroxide crystals. Many of the organic solvents commonly used in Connecticut College’s laboratories have the potential to form explosive peroxide crystals, diethyl ether and tetrahydrofuran being two of the more common. Therefore, it is extremely important that this procedure be followed regarding the identification, handling, storage, and disposal of peroxide-forming chemicals. A peroxide forming chemical is one that contains a peroxo (O-O) unit, one that has the chemical formula of O2²¯.

Under normal storage conditions the materials listed in this document have the potential to generate and accumulate peroxide crystal formations, which may violently detonate when subjected to thermal or mechanical shock. Peroxide-forming chemicals react with oxygen – even at low concentrations – to form peroxy compounds. The risk associated with peroxide formation increases if the peroxide crystallizes or becomes concentrated by evaporation or distillation. Factors that affect rate of peroxide formation include exposure to air, light and heat, moisture, and contamination from metals.

Peroxide crystals may form on the container plug or the threads of the lid and detonate when the lid is twisted. Do not open a liquid organic peroxide or peroxide-forming chemical if crystals or a precipitate are present.

Responsibilities

The Director of Environmental Health & Safety (EH&S) provides technical assistance to lab personnel about the safe handling, storage and disposal of peroxide-forming chemicals, and training as needed.

Lab personnel ensure that peroxide-forming chemicals are properly managed and disposed in accordance with this policy document.

Procedures

Purchasing Considerations

• Whenever possible, purchase only peroxide-forming chemicals which contain a peroxide formation inhibitor (e.g., tetrahydrofuran or diethyl ether inhibited with butylated hydroxytoluene (BHT)).
• Purchase only those quantities of peroxide-forming chemicals that you expect to use within expiration and disposal timeframes.

Labeling Requirements

• All bottles of peroxide-forming chemicals must have the date received marked on the container.
• When the bottle is first opened, the container must be marked with the date opened.

Sample Label

Storage and Use Requirements

Do not store peroxide-forming chemicals in direct sunlight as light can accelerate the chemical reactions that form peroxides.

• If the peroxide-forming chemical is flammable and requires refrigeration, then an explosion-proof refrigerator must be used.
• Do not distill, evaporate or concentrate a peroxide-forming chemical until you have first tested it for the presence of peroxides. (Peroxides are usually less volatile than their parent material and will tend to concentrate in the hot distillation pot).
• NEVER, UNDER ANY CIRCUMSTANCES touch or attempt to open a container of a peroxide-forming chemical if there are whitish crystals around the cap and/or in the container. The friction of screwing the cap may cause the crystals to detonate. If you encounter such a container, contact the Director of Environmental Health & Safety immediately. The Director of EH&S has contractors available to test and, if necessary, stabilize peroxide-forming chemicals.

Disposal Requirements

There are four classes of peroxide-forming chemicals, based upon the peroxide formation hazard:

• Class A – Severe Peroxide Hazard
• Class B – Concentration Hazard
• Class C – Shock and Heat Sensitive
• Class D – Potential Peroxide-Forming Chemicals

Peroxide-forming chemicals must be disposed of within 12 months of the date of purchase (receipt). Once opened, they must be disposed of as follows:

Peroxide Forming Chemicals

Class A – Severe Peroxide Hazard (Spontaneously decomposes and become explosive with exposure to air without concentration.)

Class B – Concentration Hazard (Requires external energy for spontaneous decomposition. Forms explosive peroxides when distilled, evaporated or otherwise concentrated.)

Class C – Shock and Heat Sensitive (Highly reactive and can auto-polymerize as a result of internal peroxide accumulation. The peroxides formed in these reactions are extremely shock and heat sensitive.)

Class D – Potential Peroxide Forming Chemicals (May form peroxides but cannot be clearly categorized in Class A, B, or C.)

References

National Safety Council: Data Sheet I-655 Rev. 87
NFPA: NFPA 432, Code for the Storage of Organic Peroxide Formulations
Reactive Hazards Reduction, Inc.http://www.rhr-inc.com/