Perchloric Acid

Perchloric acid is a corrosive superacid. When heated or highly concentrated, it has powerful oxidizing properties and forms potentially explosive mixtures with organic compounds. Available in various reagent grades, it is used to prepare perchlorate salts.

Its oxidizing power increases with concentration and temperature. Heated above 150°C it reacts violently with organic material and can cause explosions. The monohydrate of perchloric acid (85%) is a good room temperature oxidizer.

Perchloric acid is volatile and corrosive to metals and tissue, and closed containers holding the acid can rupture violently with prolonged exposure to heat. In its anhydrous form, perchloric acid can explode spontaneously, and concentrated forms are unstable. Other dangers include:

• The acid is very hygroscopic and produces heat when combined with water
• It causes severe skin burns and eye damage
• Inhaling its vapors or mist causes a burning sensation in the nose and throat along with lung irritation and coughing
• Prolonged or excessive exposure can cause severe coughing and vomiting
• Skin or eye contact or ingestion can produce blistering and burns

Although perchloric acid is not explosive in solution, it is still corrosive and harmful to your breathing. It should always be handled inside a chemical fume hood. At elevated temperatures, vapors from perchloric acid can condense on surfaces in chemical hood ductwork and form perchlorate salts that can be shock-sensitive and pose a serious explosion hazard.

Perchlorate crystals are explosive, and detonation can occur by heat, flame, friction, percussion, or another chemical reaction. Something as small as the vibration of the blower motor can cause a violent reaction. Fortunately, perchlorate salts dissolve in water and water neutralizes perchloric acid. Therefore, special hoods that offer complete washdown are required for work with perchlorate crystals.