The acid is extremely corrosive and is very damaging to tissue. It will form explosive mixtures with anything combustible and these mixtures may ignite or detonate without warning. The usual strength of the acid is 72%wt where it forms a constant boiling point azetope. The 70% acid is fairly stable, the anhydrous acid (100%) will explode of its own accord if stored for a period of time. It can only be stored indefinitely at liquid air temperatures.
See THE PREPARATION OF PERCHLORIC ACID. by H. H. WILLARD in 'Further Reading' section.
============= A violent explosion took place in an exhaust duct from a laboratory hood in which perchloric acid solution was being fumed over a gas plate. It blew out windows, bulged the exterior walls, lifted the roof, and extensively damaged equipment and supplies. Some time prior to the explosion, the hood had been used for the analysis of miscellaneous materials. The explosion apparently originated in deposits of perchloric acid and organic material in the hood and duct. ------------------- An employee dropped a 7-lb bottle of perchloric acid solution on a concrete floor. The liquid was taken up with sawdust and placed in a covered, metal waste can. Four hours later, a light explosion blew open the hinged cover of the can. ------------------- A stone table of a fume hood was patched with a glycerin cement and several years latter, when the hood was being removed, the table exploded when a workman struck the stone with a chisel. ------------------- During routine maintenance involving partial dismantling of the exhaust blower on a perchloric acid ventilating system, a detonation followed a light blow with a hammer on a chisel held against the fan at or near the seal between the rear cover plate and the fan casing. The intensity of the explosion was such that is was heard four miles away and of the three employees in the vicinity, one sustained face laceration and slight eye injury; the second suffered loss of four fingers on one hand and possible loss of sight in one eye; the third was fatally injured with the 6 in. chisel entering below his left nostril and embedded in the brain. [K. Everett and F.A. Graf Jr. Handling Perchloric Acid and Perchlorates. In: N.V. Steere, ed. Handbook of Laboratory Safety. Second Edition - 1971.] --donald j haarmann - eminence grise
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