The ground sample (sifter no. 4) is about 0.5 g, put into a tapered bottle, add 50 mL 70% methanol, and then measure the weight, heat and reflux for 30 minutes, let it cool, then weigh the weight, use 70% methanol to make up for the lost weight, shake well, stand still, take the supernatant, filter, and take the filtrate.