Perchloric acid is one of the strongest acids known. At room temperature, aqueous solutions up to 72% do not have significant oxidizing power, and the corrosive properties are very similar to other mineral acids. However, the oxidizing power increases with concentration and temperature. Concentrated perchloric acid (72%) heated above 150⁰C is a strong oxidizer, and reacts violently with organic material, which has resulted in devastating explosions in the past.
The monohydrate of perchloric acid (85%) is a good oxidizer at room temperature.
Anhydrous perchloric acid is highly unstable, explodes upon contact with organic material, and explodes spontaneously at room temperature after storage for a few days. Its preparation should be avoided.
Perchloric acid forms an azeotrope with water at a concentration of 72.5% perchloric acid. Therefore, aqueous solutions do not form anhydrous perchloric acid by evaporation. However, dangerous anhydrous perchloric acid can form when an aqueous solution is subjected to strong dehydrating conditions such as exposure to concentrated sulfuric acid, acetic anhydride, or phosphorous pentoxide.
At elevated temperatures, vapors from perchloric acid can condense on surfaces in the ductwork of the hood, where they form perchlorate salts that are often highly shock-sensitive and that pose a serious explosion hazard.
Perchloric acid reacts with alcohols and certain other organic compounds to form highly unstable and explosive perchlorate esters.
If you know of or suspect that perchloric acid digestions have been performed in a fume hood not specifically designed for perchloric acid, inform Facilities and Services about the location of the hood.
Rinse off affected skin immediately with copious amounts of water for about 15 min; if necessary, use the safety shower. Remove contaminated clothing.
Use the eye wash to rinse the eye thoroughly for at least 15 min, occasionally lifting upper and lower eyelids and rolling the eyeballs.
Move into fresh air immediately.
Do not induce vomiting. Rinse mouth with water.
If any symptoms persist after following first aid procedures, seek medical attention immediately. Provide the medical team with the Safety Data Sheet (SDS) for perchloric acid.
Spills of perchloric acid must be cleaned up thoroughly; dried acid residues can cause unexpected explosions in the future. The spill should be neutralized immediately with sodium bicarbonate or other inorganic acid neutralizer. Sweep up the neutralized spill with a non-flammable material and then clean the spill area thoroughly with water.
Do NOT use rags, paper towels, or sawdust to soak up perchloric acid spills. Such materials may spontaneously ignite once dried out. Likewise, spills on wood may present a fire hazard after the liquid dries.
In the event of a fire, the best extinguishing agent is water.
Store perchloric acid with other inorganic acids and away from organic chemicals and reducers, especially alcohols, glycerol, and hypophosphites. The containers should be stored in secondary containment preferably made from glass, porcelain, ceramic, or other non-absorbing, non-combustible material.
Limit stored quantities to what is needed for the next 6-12 months; do not store perchloric acid over extended periods of time.
Dispose of bottles with discolored perchloric acid solutions immediately.
Inform DRS if crystals have formed around the neck and cap of the bottle.
Collect all perchloric acid and contaminated waste and dispose of it through DRS. The UI codes are 587 for perchloric acid and 50043 for debris contaminated with perchloric acid.
Schilt, A. A. Perchloric acid and perchlorates, G. F. Smith Chemical Company: Columbus, OH, 1979.
Muse, L. A. Safe Handling of Perchloric acid in the Laboratory, J. Chem Educ. 1972, 49, A463-A464.
Furr, A. K., CRC Handbook of Laboratory Safety, 4th ed.; CRC Press LLC: Boca Raton, Florida, 1995.
NRC (National Research Council). Prudent Practices in the Laboratory. Handling and Management of Chemical Hazards. National Academy Press: Washington, DC, 2011.
Pitt, M. J. In Bretherick’s Handbook of Reactive Chemical Hazards, 6th ed.; Urben, P. G. Ed.; Butterworth-Heinemann Ltd: Oxford, 1999; Vol. 1, pp 1352-1364.