The tables at the end of this chapter summarize these data. Chemical … by intermol ecular hydrogen bonds … 2. PETTRSON The Chemical Composition of Wood 123 hydrate …58 THE CHEMISTRY OF SOLID WOOD ysis of extractives (chemotaxonomy). Chemotaxonomy is discussed fully elsewhere in the literature (1, 2). There are two major chemical components in wood: lignin (18- 35%) and carbohydrate (65- 75%). Both are complex, polymeric materials. Minor amounts of extraneous materials, mostly in the form of organic …

There are two major chemical components in wood: lignin (18- 35%) and carbohydrate (65- 75%). Both are complex, polymeric materials. Minor amounts of extraneous materials, mostly in the form of organic extractives and inorganic minerals (ash), are also present in wood (usually 4- 10%). Overall, wood has an elemental composition of about 50% carbon, 6% hydrogen, 44% oxygen, and trace amounts of several metal ions. A complete chemical analysis accounts for all the components of the original wood sample. Thus, if wood is defined as part lignin, part carbohydrate, and part extraneous material, analyses for each of these components should sum to 100%. The procedure becomes more complex as the component parts are defined with greater detail. Summative data are frequently adjusted to 100% by introducing correction factors in the analytical calculations. Wise and coworkers (3) presented an interesting study on the summative analysis of wood and analyses of the carbohydrate fractions. The complete analytical report also includes details of the sample, such as species, age, and location of the tree, how the sample was obtained from the tree, and horn what part of the tree. The type of wood analyzed is also important; i.e., compression, tension, or normal wood. Vast amounts of data are available on the chemical composition of wood. Fengel and Grosser (4) made a compilation for temperate- zone woods. This chapter is a compilation of data for many different species from all parts of the world, and includes much of the data in Reference 4. The tables at the end of this chapter summarize these data. Chemical Components Carbohydrates. The carbohydrate portion of wood comprises cellulose and the hemicelluloses. Cellulose content ranges from 40 to 50% of the dry wood weight, and hemicelluloses range from 25 to 35%. CELLULOSE . Cellulose is a glucan polymer consisting of linear chains of 1,4- ? ? -bonded anhydroglucose units. (The notation 1,4- ?? describes the bond linkage and the configuration of the oxygen atom between adjacent glucose units.) Figure 1 shows a structural diagram of a portion of a glucan chain. The number of sugar units in one molecular chain is referred to as the degree of polymerization (DP). Even the most uniform sample has molecular chains with slightly different DP values. The average DP for the molecular chains in a given sample is designated by ~…

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