Cellulose fibres isolated from wood by chemical treatments.
Note 1: The preparation of wood pulp involves the boiling of wood chips with alkaline liquors or solutions of acidic or neutral salts followed by bleaching with chlorine compounds, the object of these treatments being to remove more or less completely the hemicelluloses and lignin incrustants of the wood. The purified fibres are usually pressed into standard sheets about 1 mm thick, and commercial material retains 4-12% of carbohydrates soluble in 17.5% soda at 20°C, the actual content depending on the severity of the purification treatments.
Note 2: Mechanical wood pulp is obtained by wet-grinding bark-free wood in stone or other mills. The material is used largely in admixtures with bleached pulp for newsprint and is quite different from wood pulp as defined above in note 1.
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