Extraction of caffeine from dry tea leaves скачать в хорошем качестве

Extraction of caffeine from dry tea leaves

Procedure: You will be provided with a large tea bag containing about 15 g dry tea leaves. Place the tea bag in a 600 mL beaker, add 10 g of sodium carbonate and 150 mL of water, and boil the mixture gently for 20 minutes. Cool the dark brown aqueous solution to room temperature and squeeze the tea bag to extract the liquid fully before discarding the bag. Transfer the dark solution to a separatory funnel and extract twice with 15 mL portions of dichloromethane. Avoid vigorous shaking of the funnel since emulsions may form readily; instead, swirl the funnel gently or turn it upside down several times. After each extraction drain the denser dichloromethane layer into a small flask. Dry the combined organic extracts with anhydrous sodium sulfate until the solution is clear. Decant the dichloromethane into a small beaker and evaporate to dryness over a water bath in the fume hood. Do not heat the residue any longer than necessary since caffeine decomposes readily. Weigh the crude caffeine and calculate its percentage in the tea leaves. Determine the melting point of your product.