Bookbinding and the Conservation of Books
A Dictionary of Descriptive Terminology

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chemical wood pulp

A paper pulp prepared from both coniferous and deciduous trees, in which the LIGNIN and other undesirable materials are removed by cooking the wood with an alkaline sodium sulfide solution, or a sodium sulfite solution, leaving the cellulose fibers in an aqueous suspension of the dissolved lignins, etc. The fibers are washed and are then used "as is' to produce unbleached paper or are bleached to produce white paper.

The fibers from coniferous trees are ribbonlike and have thin walls. Generally, two distinct types of fibers can be distinguished: 1) a broad fiber of a width of about 0.05 mm and a length of about 2.5 to 4 mm, and 2) a narrower fiber about 0.02 mm wide and 1.5 to 5 mm long. The fibers of deciduous trees are shorter than those of the conifers, being between 1and 1.5 mm long, but they are usually thicker.

In chemical tests to determine the presence of chemical wood pulp in paper, an iodine-zinc chloride solution gives a pale violet, pale blue, or reddish blue, depending upon the type of chemical pulp. (93 , 98 , 143 )

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