Calculation of Lignin Concentration from Refractive Index

33 Calculation of Lignin Concentration from Refractive Index 

To calculate lignin concentration from refractive index of the specimen, calibration values are required. For measurements in the secondary wall, value Na in Eq. (3) is the refractive index of the S2 region in a matched specimen of holocellulose. This value varies from specimen to specimen and must be measured each time a new specimen is examined (Donaldson 1985a). The only exception is for earlywood and latewood from the same growth ring. For measurements in the middle lamella, Na has a constant value of 1.516 which 

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S.3.3 Calculation of Lignin Concentration from Refractive Index... 

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