![]() Together, the amount of ash and extractives in wood can vary from trace amounts to 30% and therefore affect the weight of wood differently according to species. Ash, which makes up 0.5% to 2.0% of most woods, has a specific gravity of 1.6 to 2.8 the specific gravity of extractives varies depending on the substance. These extractives and infiltrates impregnate the lignocellulosic matrix and fill parts of the cavities of the wood. In addition, inorganic compounds such as silicates, carbonates, and phosphates appear in the wood as "infiltrates" and result in ash as the wood substance is decomposed. ![]() Wood also contains measurable quantities of organic "extractives" such as such as terpenes, resins, and polyphenols such as tannins, sugars, and oils. ![]() With the specific gravity around 1.5, solid wood "substance", or lignocellulose as it is commonly called today, weighs around 1500 kg/m 3 (93.6 lb/ft 3), at theoretical most…no air, water, or other fluids in cell pores, which would decrease the weight of the wood per unit of volume. The nice thing about using water as the reference measure was that early scientists could easily classify materials by whether they float on water (specific gravity less than 1.0) or whether they sink (specific gravity greater than 1.0). Since water conveniently weighs about 1 g/cm 3, variable with temperature, specific gravity was derived as an index metric to state the weight of other substances relative to water.
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