By Wendy Conner

It might surprise you that peroxide is a danger. Almost all of us have used hydrogen peroxide at home to clean wounds or as a household cleaning aid. It is for this reason that many don’t consider it a danger. 

Common household peroxide is a 3% solution of the simple peroxide H2O2 (H-O-O-H). Peroxides and peroxide formers used in the laboratory pose a greater safety risk than the brown bottle of hydrogen peroxide in your bathroom.  

Peroxides are widely used in research laboratories because of their exceptional reactivity and oxidative capacity. The oxygen-oxygen bond in the peroxide (R-O-O-R’) is relatively weak and tends to spontaneously change to form more stable molecules.  

As a class, peroxides are exceptionally prone to violent decomposition initiated by several mechanisms…. [1] They are among the most hazardous substances commonly handled in the laboratory because they are highly flammable; extremely sensitive to shock, heat, spark, friction, impact, and light; and react readily with strong oxidizing and reducing agents. (see videos in experiment links below) 

So, what are peroxide forming compounds?  

Peroxide formers are compounds that react with the oxygen in the air or form a compound with a peroxide group when concentrated.  

The slow reaction between organic chemicals and oxygen in the air under mild conditions can produce unstable and dangerous hydroperoxide and peroxide products. This means that a bottle sitting on a shelf can, over time, become a silent ticking time bomb without you even realizing it. 

Peroxide formers are grouped into three classes based on the method of formation. (peroxide former list)   

• Class A can form explosive peroxide levels just sitting on the shelf, can form in an unopened container, and some will separate from solution. 

• Class B can form peroxides when concentrated by evaporation, distillation, etc. They are often volatile solvents, and the repetitive opening of a container could allow enough evaporation to reach an explosive level of peroxide concentration. 

• Class C are formed when the compound polymerizes. 

Common misconceptions concerning peroxide formers and why they are potentially dangerous: 

My bottle of Tetrahydrofuran has an inhibitor so it’s safe to keep around for years. – Wrong! Just because the bottle of peroxide-former has an inhibitor, it has not been rendered safe to keep beyond safety guidelines. The antioxidant inhibitors are used up binding to the oxygen over time as it prevents peroxide formation. The inhibitor will eventually deplete to a point where peroxide formation will occur. It just delays the process.  

I use ethyl ether all the time and haven’t had any accidents. I know what I’m doing….  – Accidents in laboratories happen when attention drifts, staff become complacent, or proper procedures are not followed when working with peroxide-forming compounds (see Berkley and Princeton accident reports). 

Some key points when handling and working with peroxide-forming compounds are: 

1 . Do not open the container if: 

• crystals are visibly present;
  
• precipitate has formed;
  
• an oily viscous layer is present; or  
• the container was opened more than 12 months ago, or it is past the expiration.  

2. Material must be properly disposed of by/before: 

• 12 months of opening for Class B & C;
  
• 3 months of opening for Class A and distilled peroxide-forming solvents with no stabilizer; and/or  
• expiration date on the label.  

3. If beyond the above dates: 

• do not open because it could be shock-sensitive;
  
• call Environmental Health and Safety (EHS) for technical assistance; and  
• place a Danger Warning on the container. 

4. Do not use metal spatula with peroxides.  (Watch sodium with hydrogen peroxide video)  

5. Put a warning on any container that it is a peroxide-former. (See IU CHP 3.17 for all Procedures for Safe Handling and Management of peroxide forming chemicals  ) 

It is important to know what peroxide-forming compounds are in your lab, to order only what you will use within the disposal window, and to record the date received and opened so you know if they are safe to handle. We recommend using a label like the one below to make sure laboratory personnel are aware of the possible danger and to remind you to be sure these chemicals are disposed of before they become a safety issue. Sheets of printed labels can be requested from EHS or you can print your own with the templates below.  

Don’t be caught by the peroxide-former ticking time bomb.  

 

Reference:

[1] Clark, Donald E. Ph.D. “PEROXIDES AND PEROXIDE-FORMING COMPOUNDS.” Texas A&M University, 2000, https://www.bnl.gov/esh/cms/pdf/peroxides.pdf.  

Warning Label Templates:

Peroxide former labels AVERY 5161

Peroxide former labels AVERY 5162

Videos of experiments with H2O2:

Spontaneous Combustion With H202 (Hydrogen Peroxide) by Nick Uhas 

Slow Motion Peroxide Explosion posted by Mike Davis