Appeal No. 1998-2349
Application 08/586,874
Claim 8
Takatomi discloses a method for removing iron and
chlorine from hydrochloric acid containing free chlorine and
iron (page 1). The chlorine is first removed by contacting
the hydrochloric acid with either a reductant alone or a
reductant followed by low-activated carbon, and then the iron
is removed by contacting the hydrochloric acid with a strong
basic anion exchange resin (pages 1 and 4-5). The reductant
preferably is at least one of hydrazine, hydroxylamine
chlorate, urea and hydrogen peroxide (pages 1 and 4).
Takatomi removes the free chlorine to prevent the
hydrochloric acid from being colored and to prevent the anion
exchange resin from partially losing its exchange capacity due
to being oxidized by free chlorine (page 2). Takatomi must
use low-activated carbon to remove the chlorine, because high-
activated carbon would reduce the iron such that it cannot be
thoroughly removed by the anion exchange resin (pages 2-3).
Thus, Takatomi would have fairly suggested two approaches
to one of ordinary skill in the art. One is Takatomi’s
approach, which is to carry out the chlorine removal upstream
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