copper number
A number expressing the amount of copper reduced
from the cupric to the cuprous state by a given
amount of cellulosic material. It is useful as a
measure of purity, particularly in relation to the
strength and resistance to chemical degradation of
paper and board. The copper number gives the
degraded celluloses, and particularly those that
result from bleaching. Although the copper number
test is subject to reservations, it is generally
agreed that a lower copper number enhances the
chances of longevity of the paper. The test does
not, however, apply to lignified fibers, and must
be corrected for noncellulosic constituents. (72 , 143 )
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