Distribution of Hot-Water Soluble Material in Cell Walls and Cavities of Redwood

Redwood is noted for its relatively good dimensional stability. This property is ascribed to the presence of certain extractives in the redwood. Generally, extractives may be present within the cell cavities or within the cell walls. The location of a given amount of extractives can influence the density and the swelling and shrinking characteristics of the wood. A simple procedure is described for determining the fraction of the total hot-water extractives content, present in either the wood substance or the cell cavities. Cross sections serially cut from a green bolt were slowly dried by stepwise dehumidification to equilibrium with 30 percent R. H. They were trimmed to 1 by 1 by 0.12 inches with the annual rings parallel to one edge. The specimens were ovendried at 100?C for 3 hours, weighed and measured. After being slowly raised to 97 percent R.H., they were immersed in water and extracted for 16 hours (hot water, soxhlet). Again they were slowly dried, ovendried, weighed, and measured. The aqueous extractive-containing solution was evaporated to a reddish-brown material. The weight of this material represents that of extractives removed. The density of the extract was determined. About three-fourths of the total amount of extractives is present in the cell walls, the remaining one-fourth is in the cell lumen. Since the total hot-water extractives content is high (about 18 percent), and a large fraction of this is located in the cell walls, the relatively high dimensional stability of redwood may be explained.

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