Abstract

A number of softwoods and hardwoods (beech, rubberwood, Corsican pine, Korean pine) were reacted with acetic anhydride to a variety of weight percentage gain (WPG) values and the volume change due to reaction was determined both by measurement of the external dimensions and by helium pycnometry. The volume change due to modification determined by helium pycnometry was found to be equal to that calculated, except for Corsican pine. The volume change as determined by the external dimensions was not a reliable method for determining cell-wall volume changes. The molar volume of the acetyl group in the cell wall was calculated over a range of WPG values, with volumes ranging from approximately 32 to 42 cm³ mol^-1, depending on the wood species studied. The differences in acetyl molar volume observed between most wood species were significant.