chlorine
A commonly occurring, nonmetallic, univalent and
polyvalent element (Cl), belonging to the
halogens, and used, generally in the form of
chlorine dioxide (ClO 2 ), or
hypochlorite (Ca(ClO) 2 ), as a bleach
to whiten paper pulp, usually in one or more of
the final stages in a multi-stage sequence. Its
use as a bleaching agent in paper manufacture
began in 1774 but its deleterious effects, while
noticed almost immediately, were largely
misunderstood or ignored. Chlorine residues are
extremely difficult and expensive to remove, and
many chlorine compounds break down slowly forming
highly destructive hydrochloric acid in the
process. Chlorine is also used as a disinfectant
in leather manufacture. (198 , 235 )
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