Perchloroethylene (Tetrachloroethylene, PERC)
Widely used all over the world for dry cleaning fabrics, PERC has a sweet odor that is detectable when concentration reaches about 1 part per million. Overall, the world produces just over a million metric tons per year for commercial and industrial use. This compound was first synthesized by Michael Faraday in 1821. PERC is an exceptionally useful solvent for most organic materials, with the added advantages of being volatile, highly stable, and nonflammable. Thanks to this unique composition, it is most commonly found in the dry-cleaning industry, as well as to degrease metal parts in both the metalworking and automotive industries, usually with the addition of other chlorocarbons. Paint strippers and spot removers also contain concentrations of PERC as well. One unusual use for PERC is in neutrino detectors where a neutrino interacts with a neutron in the chlorine atom and converts it to a proton to form argon.