Bookbinding and the Conservation of Books
A Dictionary of Descriptive Terminology

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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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