Perchloric Acid and Perchlorates

Abstract

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

Perchlorate Exposure and Dose Estimates in Infants

“…Perchlorate is an inorganic anion used in solid rocket fuel, explosives, and pyrotechnics (1). It forms naturally in the atmosphere and accumulates in arid regions (2, 3).…”

Perinatal Exposure to Perchlorate, Thiocyanate, and Nitrate in New Jersey Mothers and Newborns

“…Perchlorate (ClO 4 − ) is an inorganic anion used as an oxidant in solid rocket propellant, road flares, explosives, and pyrotechnics (1). Perchlorate also can form naturally in the atmosphere (2), leading to perchlorate accumulation in arid climates (3).…”

Exposure to perchlorate, nitrate and thiocyanate, and prevalence of diabetes mellitus

“…[1][2][3][4][5] As an oxidizer extensively used in rocket fuels, fireworks and other products, perchlorate can be detected in contaminated drinking water, some fertilizers and certain foods. 1,2,6,7 In addition, perchlorate can also occur naturally as a result of atmospheric processes. 8 Nitrate is frequently found in polluted water, leafy vegetables and cured meats.…”