8.9.1 Hydrofluoric Acid

Hydrofluoric Acid (HF) is one of the most hazardous chemicals at used Cornell. Small exposures to HF can be fatal if not treated properly. The critical minutes immediately after an exposure can have a great effect on the chances of a victim’s survival.

HF is a gas that is dissolved in water to form Hydrofluoric acid. The concentration can vary from very low such as in store bought products up to the most concentrated 70% form (anhydrous), with the most common lab use around 48%. The liquid is colorless, non-flammable and has a pungent odor. The OSHA permissible exposure limit is 3 ppm, but concentrations should be kept as low as possible. HF is actually a weak acid by definition and not as corrosive as strong acids such as Hydrochloric (HCl), however, corrosivity is the least hazardous aspect of HF. The toxicity of HF is the main concern.

HF is absorbed through the skin quickly and is a severe systemic toxin. The fluoride ion binds calcium in the blood, bones and other organs and causes damage to tissues that is very painful and can be lethal. At the emergency room, the victim is often given calcium injections, but pain medication is not generally given since the pain subsiding is the only indication that the calcium injections are working.

Due to the serious hazard of working with HF, the following requirements and guidelines are provided:

• All users of HF must receive EHS Hydrofluoric Acid Safety training as well as training by their supervisor. The EHS Hydrofluoric Acid Safety training is available online.
• A Standard Operating Procedure (SOP) must be written for the process in which HF is used. This SOP should be posted or readily available near the designated area where HF use will occur.
• HF should only be used in a designated fume hood and the fume hood should be identified by posting a HF Designated Area Sign (docx).
• First Aid - A HF first aid kit must be available that includes 2.5% calcium gluconate gel. The Calcium gluconate gel can be obtained at the Cornell Health dispensary with a department charge number and should be replaced with new stock annually. The Hydrofluoric Acid First Aid Sign (docx) should be posted in a prominent place where the Calcium gluconate gel is located.
• Spill Kits - An HF spill kit must be available with calcium compounds such as Calcium carbonate, Calcium sulfate or Calcium hydroxide. Sodium bicarbonate should never be used since it does not bind the fluoride ion and can generate toxic aerosols.

Prior approval - Before anyone uses HF they must have prior approval from the Principal investigator. The names of lab personnel should be added to an HF Prior Approval form showing that they have are familiar with the following:

• Has read the SDS for HF
• Has read the HF Use SOP developed by the lab
• Has read the Hydrofluoric acid section in this Lab Safety Manual
• Is aware of the designated area for HF use
• Knows the first aid procedure in case of an HF exposure
• Knows what to do incase of an HF spill

Personal Protective Equipment (PPE) – The following PPE is required for HF use:

• Rubber or plastic apron
• Plastic arm coverings
• Gloves
  • Incidental use - double glove with heavy nitrile exam gloves and re-glove if any exposure to the gloves
  • Extended use – heavy neoprene or butyl over nitrile or silver shield gloves
• Splash goggles in conjunction with a fume hood sash
• Closed toed shoes
• Long pants and a long sleeve shirt with a reasonably high neck (no low cut)

The following are safe practice guidelines when working with HF:

• Never work alone with HF but have a buddy system.
• Use a plastic tray while working with HF for containment in case of a spill.
• Keep containers of HF closed. HF can etch the glass sash and make it hard to see through (if the hood sash becomes fogged and hard to see though due to etching, then please contact EHS at 607-255-8200 about installing a polycarbonate sash)
• Safety Data Sheet (SDS) – A SDS for HF must be available.
• All containers of HF must be clearly labeled. Secondary labels for all non-original containers can be printed from Chemwatch.
• The stock HF should be stored in plastic secondary containment and the cabinet should be labeled. HF should be stored in lower cabinets near the floor.
• Wash gloves off with water before removing them. 

Additional information on the safe use and handling of Hydrofluoric acid (HF) can be found on the Honeywell website - the world's largest producer of Hydrofluoric Acid. This website contains useful information on HF such as:

• Safety Data Sheets
• Technical Data Sheets
• Recommended Medical Treatment for HF exposure
• HF Properties charts
• Online Training

8.9.2 Perchloric Acid

Perchloric acid is a strong oxidizing acid that can react violently with organic materials. Perchloric acid can also explode if concentrated above 72%. For any work involving heated Perchloric acid (such as in Perchloric acid digestions), the work must be conducted in a special Perchloric acid fume hood with a wash down function. If heated Perchloric acid is used in a standard fume hood, the hot Perchloric acid vapors can react with the metal in the hood ductwork to form shock sensitive metallic perchlorates. When working with Perchloric acid, be sure to remove all organic materials, such as solvents, from the immediate work area. Due to the potential danger of Perchloric acid, if possible, try to use alternate techniques that do not involve the use of Perchloric acid. If you must use Perchloric acid in your experiments, only purchase the smallest size container necessary.

Because Perchloric acid is so reactive, it is important to keep it stored separate from other chemicals, particularly organic solvents, organic acids, and reducing agents. All containers of Perchloric acid should be inspected regularly for container integrity and the acid should be checked for discoloration. Discolored Perchloric acid should be discarded as hazardous waste. Perchloric acid should be used and stored away from combustible materials, and away from wooden furniture. Like all acids, but particularly with Perchloric acid, secondary containment should be used for storage.