Perchlorates are the salts derived from perchloric acid. They are used as oxidizers for fireworks, airbags and in solid rocket fuel. The solid rocket boosters of the space shuttle contain 350 metric tons of ammonium perchlorate each.
Perchlorate compounds are derived from perchloric acid (HClO4), a strong mineral acid that is an explosion hazard. When perchloric acid vapors combine with organic or metallic ions they form perchlorate compounds. Common organic and metallic perchlorates include ammonium perchlorate (NH4ClO4), potassium perchlorate (KClO4) and sodium perchlorate (NaClO4). Dry crystals of perchlorate pose an explosion hazard if disturbed. Perchlorates are strong oxidizers that are widely used because they are generally stable, however if heated or shocked they may ignite or detonate.
Perchlorate residues can be encountered within fume hoods and exhaust ductwork of laboratories in which perchlorate or perchloric acid is used. Perchlorate residues can be identified in the field using methylene blue solution, which forms a violet precipitate after reacting with the perchlorate ion. In addition to field testing, perchlorate residues can be detected by laboratory analysis of wipe samples. Best management practices for laboratory cleaning include drenching with water following use to remove potential residues, and the disposal of solutions by dilution in copious amounts of water.
Perchlorates have also been identified as a contaminant in soil and groundwater in Massachusetts, and as an Emerging Contaminant by the US EPA. Perchlorates are also naturally occurring compounds that have been detected at low concentrations in arid areas and on Mars. Perchlorates are extremely soluble in water, making them relatively easy to remove in laboratory conditions; however the solubility makes cleanup of perchlorates in the environment difficult because they do not readily degrade.
MA DEP Perchlorate Q&A: http://www.mass.gov/dep/toxics/pchlorqa.htm
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