Phenolic Hydroxyls in Lignin

Hydroxyl groups were measured using the spectroscopic method [14] and the conduc-timetric method [ 15] as described below. 

Conductimetric method - Between 0.2 and 0.3 g lignin were suspended in 10 mL ethanol and submitted to magnetic agitation. Then, 5 mL acetone and 15 mL distilled water were added, producing a fine lignin suspension. The suspension was bubbled 

Spectroscopic method - Approximately 0.2 g lignin of known moisture content was dissolved in 50 mL dioxane (96%) and the solution was diluted 1 10 in dioxane and then 1 1 in water and the pH was adjusted to 13 by addition of 1 mol. NaOH. A control was prepared with the same dilution but with the pH adjusted to 1 by addition of 1 mol. HCl. The average lignin value was used to calculate the percent phenolic OH. 

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