Lignin content

To determine ash-free lignin content, 1 g of sample is treated with 20 ml of 72% sulfuric acid in a 100 ml beaker, stirred, and left overnight at room temperature. The mixture is then diluted to 3% sulfuric acid in a 1-liter flask and boiled under reflux for 4 hours. The lignin is filtered, washed with hot distilled water until neutral, dried, and weighed. The sample is ignited at 850°C for 45 minutes, and the ash weight is subtracted to calculate the ash-free lignin percentage.

By Allschoolabs · August 2, 2025 · 50 views

About 1 g (exactly weighed) of the extracted sample is put in a 100 ml beaker and then treated with 20ml of 72% sulfuric acid, added to the sample drop by drop with constant stirring by a small glass rod. After complete disintegration, the reaction is allowed to stand and the beaker is covered with a watch glass and left over night at room temperature. It was then transferred quantitatively to a 1 liter round bottom flask, diluted to 3% sulfuric acid, and boiled for four hours under reflux. The lignin is filtered on an ashless filter paper and washed with hot distilled water till neutrality, then gravimetrically estimated and ignited at 850°C for 45 minutes. The weight of ash is subtracted to give the ash-free lignin per cent.