Formation of Peroxides

Different organic compounds form peroxide by a free reaction of the hydrocarbon with molecular oxygen, and the catalyst by light and heat causes this process. Peroxides form when materials are exposed to oxygen, and a material’s potential for hazardous peroxide formation depends on its molecular structure. Based on use guidelines, peroxide forming chemical materials are classified into three categories, each with general handling and peroxide formation susceptibility.

Potential Peroxide-Forming Solvents

Group A: Chemicals stored for a long time after being exposed to air form explosive levels of peroxides without concentration. Test for peroxide material or dispose of the chemical after three months.

Group B: A chemical that forms explosive levels after concentration. Test it before discarding and test monthly for peroxide formation after opening and reduce it if present after 12 months.

Group C: The chemicals that auto polymerise result from peroxide formation. In order to prevent the polymerisation reaction, these chemicals are stored with polymerisation inhibitors. For such chemicals, test it for peroxide formation after opening and if found any peroxides are present after 12 months, reduce it. Before discarding the chemicals, tests for peroxide levels and inhibited chemicals are supposed to be disposed of after 24 hours. And do not store these chemicals under the inner atmosphere.

Group D: This group contains chemicals capable of forming peroxides but can not be placed under group A-C. You should test the peroxide levels quarterly.

Uses and Storage of Peroxide-Forming Solvent

Solvents like tetrahydrofuran, diethyl ether, glycol ether and cyclohexene are used in the laboratory and come under Group B. They produce organic peroxide that doesn’t evaporate easily compared to the solvent in which they form. As a result of this, the distillation can produce dangerous levels of peroxides. Most of the group B solvents evaporate easily, so the multiple opening of the container can cause dangerous peroxide concentrations.

Minimising the Hazards of Peroxidisable Compounds

People who handle or study the peroxidisable materials should know how to handle these compounds safely. This includes safe handling practices, effective purchasing decisions, a strong control program and proper disposal of hazardous containers.

Purchasing

The purchasing of peroxidisable compounds should be restricted to ensure that the chemicals are used up completely before the formation of peroxides. Researchers should not stock up on the materials but buy only the quantity needed to experiment. The testing should be done regularly to ensure the peroxides are not formed.

Storage and Shelf Life

Peroxide forms in material because of the exposure to oxygen and the function of age. Therefore, the researchers need to be aware of the handling and the age of peroxidizable materials. The researchers should have a proper dating system of the container when they were opened for the first time, and even the testing or experiment dates should also be noted on sheets. Peroxide materials should be stored away from light and also in airtight containers.

The following is a general guide for the handling of peroxidizable solvents:

• Keep a record of used substances and regular testing to detect peroxides.
• Unpacked materials should be checked regularly for peroxide formation and treated with care.
• Before conducting distillation or evaporation, check all solvents for peroxides.
• Keep such materials away from light and heat in airtight containers.

Peroxide Detection

Several methods are available to detect peroxide in a substance. The 100ppm controls the peroxide concentration in a solvent. The other one is by observing the solvent to see whether there are any crystals in it or any oily dense layers, which indicate the presence of dangerous high peroxide levels. You can also use test strips, immerse in the substance for one second, wait until the colour stabilises, and compare it with a colourimetric scale and the toolkit. The strips give a 1-100ppm range to determine if the substance is below the control point.

Management and Disposal of Old Containers

Older containers with no label or data should be handled with care and are restricted to be opened by researchers. If found in any container, then immediately contact EH&S. These peroxidizable chemicals with oil layers, crystallisation and wisp-like structures can potentially explode. If any of these conditions are seen in the container, do not try to open or move it. Instead, call the EH&S immediately for assistance.

Conclusion

Peroxidizable materials react with oxygen, resulting in the formation of peroxides capable of exploding from impact, friction or heat. Perchloric acid is a compound usually encountered as an aqueous solution, and it is a colourless compound and is a strong acid compared to sulfuric and nitric acids. Peroxide forming chemicals are a class of compounds that can form shock-sensitive explosive peroxide crystals. Many of these solvents are primarily used in laboratories and can form explosive peroxide crystals. The most common peroxide forming chemicals are diethyl ether and tetrahydrofuran.