Time-Sensitive Chemicals

• Introduction
• Peroxide Forming Solvents
  • Chemicals that form explosive levels of peroxides without concentration
  • Chemicals that form explosive levels of peroxides on concentration
  • Monomers which form peroxides that can initiate explosive polymerization
  • General Guidelines
  • Testing
• Time-Sensitive Compressed Gas Cylinders
  • General Guidelines
• References

---

Introduction

Many chemicals have a shelf-life and can become more hazardous as time goes on. This webpage discusses two classes of time-sensitive hazardous chemicals: peroxide forming solvents and certain compressed gas cylinders. It is Extremely important that these chemicals are identified and managed properly. If any time-sensitive chemicals are found to be past the manufacturer’s expiration date, they must be submitted to EHS for hazardous waste disposal immediately.

It is important to note that the time-sensitive chemicals listed on this webpage are not comprehensive. Researchers should always review the material safety data sheets for information regarding time-sensitive chemicals and expiration dates.

---

Peroxide Forming Solvents

Autoxidation in common laboratory solvents can lead to unstable and potentially explosive peroxide formation. The reaction can be initiated by exposure to air, heat, light, or contaminants. Most of these solvents are available with inhibitors to slow the peroxide formation. Examples of inhibitors include BHT (2,6-di-tert-butyl-4-methyl phenol) and Hydroquinone. There are three categories of peroxide formers:

1. Group A chemicals are those which form explosive levels of peroxides after prolonged storage, especially after exposure to air without concentration. Test these for peroxide formation before using and discard 3 months after opening. 

Butadiene	Divinylacetylene	Tetrafluoroethylene
Chloroprene	Isopropyl ether	Vinylidene chloride

2. Group B chemicals form peroxides that are hazardous only on concentration by distillation or evaporation. Test these before distillation and discard after 12 months. 

Acetal	Dicyclopentadiene	Methyl isobutyl ketone
Acetaldehyde	Diethyl ether	4-Methyl-2-pentanol
Benzyl alcohol	Diethylene glycol dimethyl ether	2-Pentanol
2-Butanol	Dioxane	4-Penten-1-ol
Cumene	Ethylene glycol dimethyl ether	1-Phenylethanol
Cyclohexanol	4-Heptanol	2-Phenylethanol
2-cyclohexen-1-ol	2-Hexanol	2-Propanol
Cyclohexene	Methylacetylene	Tetrahydrofuran
Decahydronaphthalene	3-Methyl-1-butanol	Tetrahydronaphthalene
Diacetylene	Methylcyclopentane	Vinyl ether

3. Group C chemicals consists of monomers which form peroxides that can initiate explosive polymerization. Inhibited monomers should be tested before use and discarded after 12 months. Uninhibited monomers should be discarded 24 hours after opening.

Acrylic acid	Methyl methacrylate	Vinyl chloride
Acrylonitrile	Styrene	Vinyl pyridine
Butadiene	Tetrafluoroethylene	Vinyladiene chloride
Chloroprene	Vinyl acetate
Chlorotrifluoroethylene	Vinyl acetylene

General Guidelines

• Solvents containing inhibitors should be used whenever possible.
• All peroxide forming solvents should be tested prior to distillation.
• Peroxide forming solvents should be purchased in limited quantities.
• Peroxide forming solvents should be marked with the purchase date and the date opened.
• Peroxide forming solvents should be sealed tightly and stored away from light and heat.
• Periodic testing should be done on opened containers and the results marked on the containers.

Testing

• Obtain test strips for the range of 0-100 ppm peroxide
• Record the test results on the bottle
• If the test results are 100 ppm or greater, arrange for EHS disposal

---

Time-Sensitive Compressed Gas Cylinders

• Hydrogen Fluoride, Anhydrous
• Hydrogen Bromide, Anhydrous
• Hydrogen Sulfide, Anhydrous
• Hydrogen Cyanide, Anhydrous
• Hydrogen Chloride, Anhydrous

The compressed gases listed above have a shelf-life provided by the manufacturer that must be strictly followed. There have been numerous incidents involving these compounds related to storage past the expiration date. For example, Hydrogen fluoride (HF) and Hydrogen bromide (HBr) cylinders have a shelf-life of one to two years, depending on the vendor. Over time, moisture can slowly enter the cylinder, which initiates corrosion. As the corrosion continues, HF and/or HBr slowly react with the internal metal walls of the cylinder to produce Hydrogen. The walls of the cylinder weaken due to the corrosion, while at the same time the internal pressure increases due to the Hydrogen generation. Ultimately, these cylinders fail and create Extremely dangerous projectiles and a toxic gas release (Figure 1).

General Guidelines

• Acquire gases in the smallest quantity and concentration necessary.
• Record the date the compressed gas was received. The shelf-life vendor recommendation must be strictly followed. Once a compressed gas cylinder has exceeded its expiration date, arrange disposal through EHS.
• Routinely inspect gas cylinders for evidence of deterioration or elevated pressure.

Figure 1: 30-year old HF cylinder that exploded at Purdue in 2011

---

References

• Chemical Health and Safety, Vol. No. 3, No. 5, “Review of Safety Guidelines for Peroxidizable Organic Chemicals", September/October 1996, pp. 28-36