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TAPPI T 204 Extractives soxhlet






Solvent extractives of wood and pulp


TAPPI T 204 describes a procedure for determining the amount of solvent-soluble, non-volatile material in wood and pulp. Three different solvent systems may be employed, the selection depending on the safety and reproducibility requirements of each particular laboratory. In general, dichloromethane extraction gives lower amounts of extractives than either acetone or ethanol/benzene. Extraction with 1/3 ethanol and 2/3 benzene typically gives the highest level of extractives due to the additional dissolution of low molecular weight carbohydrates and polyphenols. These generalizations do not apply to all wood species, including some tropical hardwoods containing high molecular weight polyterpene resins. Because of health, safety and regulatory concerns associated with the use of benzene and dichloromethane, acetone has been added as an alternative solvent for the determination of extractives in wood and pulp.


Soluble materials or extractives in wood consist of those components that are soluble in neutral organic solvents. The amount of solvent extractable matter is markedly influenced by seasoning or drying of the wood. The dichloromethane-extractable content of wood is a measure of such substances as waxes, fats, resins, sterols and non-volatile hydrocarbons. The ethanol-benzene extractable content of wood consists of certain other dichloromethane-insoluble components, such as low-molecular-weight carbohydrates, salts, polyphenols and other water-soluble compounds in addition to those substances previously mentioned. Since the pulping process usually removes most water-soluble and volatile compounds that are also soluble in organic solvents, the solvent extractable material in pulp may be considered to consist primarily of resin and fatty acids and their esters, waxes, and unsaponifiable substances. No single organic solvent is capable of removing all these substances and different solvents remove different combinations of components. The ethanol-benzene mixture appears to provide the most complete removal of residual solvent-extractable substances in pulp.


This test is performed in duplicate. For pulps, submit at least 25 grams of air-dried material for each solvent used. For wood samples, submit at least 5 grams of air-dried sawdust for each solvent used.


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