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 )