The densities of acid-chlorite delignified Asplund spruce fibres with degrees of delignification between 0 and 62.4 were determined. The density measurements were carried out at 23 C in mixtures of carbon tetrachloride and toluene, using a density gradient column. The density of the dry fibres increased linearly with decreasing lignin content and the density of lignin and holocellulose in situ were found to be 1397 and 1541 kg/m3respectively. Assuming a density of 1559 kg/m3for a-cellulose, the density of hemicellulose in situ was calculated to be 1520 kg/m . The physical implications of the measured values are discussed. It is concluded that there is no change in the density of holocellulose or lignin between 20 and 62.4 delignification. It is suggested that the densification of the fibre during the initial stage of delignification is due to increased order in the hemi-celluloses.
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