Perchloric acid [7601-90-3], HClO 4 , is one of the strongest of the mineral acids. The perchlorates are more stable than the other chlorine oxyanions, ie, chlorates, ClO À 3 ; chlorites, ClO À 2 ; or hypochlorites, OCl À (3) (see DICHLORINE MONOXIDE, HYPOCHLOROUS ACID, AND HYPOCHLORITES). Essentially, all of the commercial perchlorate compounds are prepared either directly or indirectly by electrochemical oxidation of chlorine compounds (4-8) (see CHLORINE; ELECTROCHEMICAL PROCESSING, INTRODUCTION). The perchlorates of practically all the electropositive metals are known, except for a few cations having low charges.The most outstanding property of the perchlorates is their oxidizing ability. On heating, these compounds decompose into chlorine, chlorides, and oxygen gas. Aqueous perchlorate solutions exhibit little or no oxidizing power when dilute or cold. However, hot concentrated perchloric acid is a powerful oxidizer and whenever it contacts oxidizable matter extreme caution is required. The acidified concentrated solutions of perchlorate salts must also be handled with caution. Ammonium perchlorate [7790-98-9] (AP) is one of the most important perchlorates owing to its high (54.5%) O 2 content and the absence of residue on decomposition. These properties, along with a long shelf life, make it a useful rocket propellant (see EXPLOSIVES AND PROPELLANTS) (9). AP is a true explosive as demonstrated by the explosion at the PEPCON plant at Henderson, Nevada, in 1988 (10).Following early (1890s) work ( 11), France, Germany, Switzerland, and the United States began to produce perchlorates for use as propellants and explosives. Whereas total world production of perchlorates did not exceed 1800 t/yr until 1940, it increased dramatically during World War II to about 18,000 t/yr in order to supply the rocket and missile industries. Actual perchlorate production is difficult to determine in any given year, because AP is classified as a strategic material. Future production is expected to depend mostly on space programs. Properties2.1. Chlorine Heptoxide. The anhydride of perchloric acid is chlorine heptoxide [10294-48-1], Cl 2 O 7 , also known as dichlorine heptoxide. It is obtained as a colorless oily liquid by dehydration of perchloric acid using a strong dehydrating agent such as phosphorus pentoxide, P 2 O 5 (12,13):The Cl 2 O 7 decomposes spontaneously on standing for a few days. The acid dehydration reaction requires a day for completion at À108C and explosions can occur. Upon ozonation of chlorine or gaseous ClO 2 at 308C, Cl 2 O 7 is formed (13). Chlorine heptoxide is more stable than either chlorine monoxide or chlorine dioxide; however, the Cl 2 O 7 detonates when heated or subjected to shock. It

Perchlorates are chlorine oxyanions in which the chlorine is present in its highest oxidation state (+7). The most outstanding property of the perchlorates, which are more stable than other chlorine oxyanions, is their oxidizing ability. Most cations form perchlorate compounds. Commercially, one of the most important compounds of this class is ammonium perchlorate, used as an oxidizer in propellant formulations for solid rocket fuel. Perchlorates are also used in explosives and pyrotechnics, in dry batteries, and in oxygen‐generation systems. Commercial perchlorates are prepared by electrochemical oxidation. Perchloric acid, commercially available as a 72% aqueous solution, is one of the strongest of the mineral acids. Properties, manufacturing, and uses of these compounds are described.

Perchlorates are chlorine oxyanions in which the chlorine is present in its highest oxidation state ( \documentclass{article}\pagestyle{empty}\begin{document}${{\rm{+}}7}$\end{document} ). The most outstanding property of the perchlorates, which are more stable than other chlorine oxyanions, is their oxidizing ability. Most cations form perchlorate compounds. Commercially, one of the most important compounds of this class is ammonium perchlorate, used as an oxidizer in propellant formulations for solid rocket fuel. Perchlorates are also used in explosives and pyrotechnics, in dry batteries, and in oxygen‐generation systems. Commercial perchlorates are prepared by electrochemical oxidation. Perchloric acid, commercially available as a 72% aqueous solution, is one of the strongest of the mineral acids. Properties, manufacturing, and uses of these compounds are described.