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Halogenated
solvents
Halogenated refers to a chemical compound or mixture that contains
halogen atoms, i.e. fluorine, chlorine, bromine, or iodine.
Bonding to carbon the halogens form a class of compounds called
covalent halides, i.e. they are not electroylytic in nature.
Some other terms for these compounds are halocarbons (halogenated
hydrocarbons), chlorocarbons and chlorofluorocarbons (CFC's,
a class of molecules containing chlorine, fluorine, and carbon).
Chlorinated solvents include the following: chloroform, chlorobenzene
, trichloroethylene, carbon tetrachloride, chlorinated fluorocarbons,
methylene chloride (dichloromethane), tetrachloroethylene (perchloroethylene),
1,1,1-trichloroethane (methyl chloroform, chlorothene). There
used to be many industrial and commercial applications for the
halogenated solvents due to their excellent ability to dissolve
oils, their fast evaporation rates and their chemical stability
(they are not flammable). Major uses in cleaning were e.g. as
dry cleaning fluids, degreasing solvents, electrical cleaning
solvents, inks and paint strippers. Solvent wastes are often
segregated into halogenated and non-halogenated waste because
it costs more to dispose of halogenated materials and because
halogenated wastes are sometimes incompatible with other wastes.
Because halogenated organic solvents are often environmental
and health hazards and even human carcinogens, the use in open
applications has been banned worldwide. However in the view
of several cleaning experts the application of perchloroethylene
(PER, PERC) in modern sophisticated air tight plants is still
useful for especially difficult cleaning problems, because high
quality results can be achieved for very complex geometries
with minimum energy input at short process times.
KK, 22.12.07
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