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Handling Perchloric Acid

See requirements for UC San Diego researchers working with perchloric acid.

Perchloric acid (HClO4) is a colorless, odorless, fuming liquid that is miscible with water and extremely corrosive. If your lab inventory includes perchloric acid, follow these guidelines to protect yourself from injury.

Requirement for researchers

UC San Diego researchers working with perchloric acid must follow an approved hazard control plan (HCP) obtained through the HCP application.

This HCP must be preapproved by the principal investigator prior to beginning any work with this material. Information on this Blink page is supplementary and is not intended to replace the approved HCP.

Never work alone when working with hazardous chemicals.

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Obtain approval before beginning work.

Get approval from your principal investigator before beginning a project involving perchloric acid.

  • If concentrations greater than 85% will be used, special precautions are required. Contact the EH&S Chemical Hygiene Officer, (858) 822-1579, before beginning work.

Evaluate the hazards before beginning work.

Evaluate the hazards before beginning work:

  • Consult safety resources:
  • Consider these hazards specific to perchloric acid:
    • Health hazards:
      • Irritatation of the skin, eyes, and respiratory tract
      • Painful burns and even death when exposed body parts come in contact with perchloric acid
    • Explosion hazards:
      • Anhydrous (dehydrated) perchloric acid: Perchloric acid is noncombustible. However, anhydrous perchloric acid and certain perchlorate salts of organic, organometallic, and inorganic cations present a serious explosion hazard due to their unstable nature and ability to react violently with many organic materials (e.g., wood, paper, cotton, etc.).
      • Aqueous perchloric acid can cause violent explosions if operations cause concentration or evaporation, or if it's in concentrations greater than normal commercial grade strength (72%). At concentrations less than 72%, aqueous perchloric acid will not decompose spontaneously.
    • Hot, concentrated solutions are extremely dangerous.
      • When used cold, 70% perchloric acid acts as a strong acid and is not considered to be a strong oxidizing agent.
      • When heated, perchloric acid acts as a strong oxidizing agent.
        • Important: NEVER heat perchloric acid in a regular fume hood. Use a wash-down type fume hood. Contact the EH&S Chemical Hygiene Officer, (858) 822-1579, for more information.
      • More concentrated solutions are strong oxidizers, and increases in temperature increase the oxidizing power of perchloric acid.
    • Do not use perchlorates as drying agents if there is any possibility of contact with organic compounds or of proximity to a dehydrating acid strong enough to concentrate the perchloric acid (e.g., a drying train that has a bubble counter containing sulfuric acid). Use a safer drying agent.

Control the hazards.

Perform a dry run of your process to work out any potential pitfalls.

  • Use less dangerous, more stable products when you can.
  • Restrict access to the work area.
  • Keep container sizes and quantities in the work area as small as possible.
  • Line work surfaces with removable plastic-backed absorbant paper.
  • Isolate perchloric acid from organic materials.
    • Do not store in wooden cabinets or on paper-lined shelves.
  • Required for evaporations:
    • Contact the EH&S Chemical Hygiene Officer, (858) 822-1579, before attempting to perform any perchloric acid evaporations.
    • Conduct evaporations of perchloric acid only in a wash down hood.
      • Specifically designed for perchloric acid use, these special fume hoods allow systematic washdowns with water after evaporations, putting the perchlorates back into solution and avoiding inadvertent explosions due to shock or heat.

    Important: If perchloric acid is inappropriately heated in a standard fume hood, accumulation of perchlorates in the fume hood or the associated duct work can make servicing the hood dangerous.

    If you suspect equipment has been contaminated with perchloric acid, contact the EH&S Chemical Hygiene Officer, (858) 822-1579. The following actions are required before the fume hood can be serviced or placed in operation:

    • Have the hood tested for perchlorates by a qualified outside vendor.
    • If test results are positive for perchlorate contamination, remediation of the fume hood and associated duct work must be performed by a qualified vendor before the room and fume hood can be cleared.
      • Contact the EH&S Chemical Hygiene Officer, (858) 822-1579, for qualified vendors.
      • The PI or the department responsible for the equipment is responsible for testing and remediation.

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