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Section 7K: Pyrophorics

Dangerous
Combustible

Certain stock reagents and in-situ products are pyrophoric, reacting violently when exposed to water and humid or dry air. These chemicals are useful to research and many are essential to catalyze certain reactions or are incorporated into final products. To handle these materials safely, review the Aldrich technical bulletins "Handling Air-Sensitive Reagents" and "Handling Pyrophoric Reagents". Some examples of pyrophoric materials include:

  • organo-metallic reagents (i.e. Grignard reagents)
  • alkali earth elements (sodium, potassium, cesium)
  • finely divided metals (Raney nickel, aluminum powder, zinc dust)
  • metal hydrides (sodium hydride, germane, lithium aluminum hydride)
  • alkyl metal hydrides (butyllithium, trimethylaluminum, triethylboron)
  • metal carbonyls (nickel carbonyl, iron pentacarbonyl)
  • gases (arsine, diborane, phosphine, silane)
  • silicon halides (dichloromethylsilane)

Exposure to air or moisture can cause these materials to evolve heat, fire, flammable or corrosive byproducts by violent decomposition. Since they are typically packaged and stored under an inert atmosphere, under oil, or within a solvent, appropriate methods must be utilized to preserve the material during storage and while dispensing. See Section 7E Highly Toxic Gases for work with pyrophoric gases.


Required Work Practices

Detailed information about transferring pyrophorics can be found in Aldrich technical bulletins "Handling Air-Sensitive Reagents" and "Handling Pyrophoric Reagents".

The following general guidelines must be followed while working with pyrophoric materials.

  • Know the properties and hazards of all chemicals you are using through adequate research and study, including reading the label and MSDS.
  • Select and obtain all necessary materials to dispense and use the reagent(s) safely.

    • Dryboxes are used to supply an inert atmosphere to prevent pyrophoric reactions with air.
    • Fumehoods do not supply an inert atmosphere; however, they can be used for ventilation and staging the reaction apparatus. The sash should be kept lowered to assist with containment in event of a violent reaction and to provide a barrier between the lab worker and the reaction.
    • Flex syringes (double-tipped needles) can be used for transferring materials.

      • Flex Syringes are constructed of tubing with needles attached to both ends for materials transfer through septa. A supply of low-pressure inert gas can be used to introduce the material to a reaction vessel, graduated addition funnel or graduated syringe. Tubing with a single needle may be needed to introduce the inert gas.
      • Flex Syringe

      • Appropriate glassware and reaction equipment

        • Ensure your glassware is DRY before assembly and introducing pyrophorics
        • Thoroughly purge all air from the apparatus with the proper inert gas
        • Use secure fittings, keep air-tight with a light coat of vacuum grease
        • Secure septa to all addition/withdrawal orifices
        • Incorporate bubblers filled with mineral oil to prevent air backflow
        • Use pressure rated glassware and fittings for pressurized reactions

      • Inert gas for purging air and material transfer

        • Nitrogen is not suitable for all materials, consult the MSDS

    • Syringes may also be used to withdraw small quantities of liquid reagent (<50 mL) from containers when a supply of inert gas is provided to displace the quantity withdrawn.

      • Ensure the syringe is completely DRY and purged with appropriate inert gas
      • Insert a line inot the septum, connected to a mineral oil-filled bubbler to prevent overpressure (not shown in picture below)
      • Insert a low-pressure inert gas source line into the septum
      • Insert an extraction syringe into the septum and slowly withdraw reagent
      • Extraction Syringe

    • Select and use the appropriate personal protective equipment, see below.
    • Never work alone with pyrophorics. Ensure someone can see or hear you.
    • Purchase quantities that will ensure use of the entire product within one year.
    • Use containers with transfer septa (i.e. Aldrich Sure/Seal) for liquid reagents.

      • septa prevent exposure to air and moisture and allow you to safely transfer the pyrophoric material when an inert working atmosphere is not available.

    • Visually check the container and reaction vessel septa for degradation before use.
    • A MetL-X fire extinguisher or powdered lime should be available in the lab.

      • ABC and CO2 extinguishers can cause some pyrophorics to react more vigorously.
      • Powdered lime can be used to cover spills and slow the reaction with air/humidity.

        • Lime is hydroscopic; keep storage containers closed to prevent absorption of atmospheric moisture.

    • Do not clean up spills. Contain the spill and/or extinguish the fire only if you can do so safely. Evacuate the lab and contact Baylor PD (2222 from a campus or 254-710-2222 from a cell phone) immediately.


Recommended Personal Protective Equipment

  • Wear closed toed shoes made of a nonporous material, leather is preferred.
  • Use a face shield and chemical splash goggles to protect your face.
  • Wear a cloth labcoat or apron that can be quickly removed if needed.

    • Do not use plastic that can melt and adhere to your clothing/skin in event of a fire.

  • Use gloves made of a material resistant to the solvent/reagent.
  • Fire-resistant outer gloves with good dexterity are recommended.
  • Know where the nearest safety shower is from the reaction area.


In The Event Of An Emergency

  • If there is fire on your clothing or skin, stop-drop-and roll, unless you are within a few feet of a safety shower.
  • Keep in mind that unreacted materials may reignite until they are washed off.
  • If you are contaminated with a pyrophoric, remove your contaminated clothing while using the safety shower. The copious amounts of water will flush away the heat of reaction. If you have significant amounts of dry reactive compound on your body, you may brush off the bulk of it before you enter the shower, however only if it is not reacting.
  • Do not clean up spills. Contain the spill and/or extinguish the fire only if you can do so safely. Evacuate the lab and contact Baylor PD (2222 from a campus or 254-710-2222 from a cell phone) immediately.
  • A MetL-X fire extinguisher or powdered lime should be available in the lab.

    • ABC and CO2 extinguishers can cause some pyrophorics to react more vigorously.
    • Powdered lime can be used to cover spills and slow the reaction with air/humidity.


Additional Related Resources

Detailed information about transferring pyrophorics can be found in Aldrich technical bulletins "Handling Air-Sensitive Reagents" and "Handling Pyrophoric Reagents".

The following articles account a fatal incident involving a UCLA researcher working with t-butyllithium. "Deadly UCLA lab fire leaves haunting questions", "Researcher Dies After Lab Fire - UCLA research assistant burned in incident with tert-butyl lithium"

A peer-reviewed publication "Safe handling of organolithium compounds in the laboratory" made available by the Division of Chemical Health and Safety of the American Chemical Society.


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