Perchloric acid use has long been associated with some violent explosions. From a safety viewpoint, one main feature of the accidents has been the severity of the accident and the fact that the persons involved are often experienced workers. The basic cause of accidents involving perchloric acid is due to contact with organic material, or a reducing material. For any use of the acid, a review of the MSDS from each manufacturer is strongly recommended.
Perchloric acid is a water white liquid, it has no odor, the boiling point at atmospheric pressure is 203C, and under high vacuum, a 73.6% composition can be produced. The acid can be dangerously reactive. At ordinary temperatures, 72% perchloric acid reacts as a strong nonoxidizing acid. At elevated temperatures (approximately 160C, it is an exceedingly strong and active oxidizing agent as well as a strong dehydrating agent. Contact with combustible material at elevated temperatures may cause fire or explosion.
When considering the hazards involved in the use of perchloric acid it should be clearly recognized that many of the reported serious laboratory accidents involved only small quantities (<1g) of reactant. The CRC Handbook of Laboratory Safety cites the Perchloric acid-Acetic Anhydride-Acetic Acid system, which if used improperly can lead to explosions. The example shows that 1 g of the mixture instantaneously produces about 7 liters of gas at the explosion temperature of 2400C. There are many other illustrations and examples, but several things should be very clear to the reader. Specifically, no one should attempt to use perchloric acid who is not fully conversant with the chemistry of the material, who has not made a careful appraisal of the operating conditions and techniques, and who exhibits any unsafe attitude about their work. Each user of the material should also recognize that any acid digestion type usage must occur in a designated perchloric acid fume cupboard, and that such usage should be reported to HSEO. Finally, each user should recognize that dangerous secondary reactions can occur with reactive perchlorate compounds formed from the acid liquid or vapors in fume cupboards, storage cabinets, and laboratory benches or floor areas.