月 Experimental section Use a piece of filter paper with many small holes to cover and seal the evaporating dish, and cover a suitable funnel on it to set up the sublimation device Heat to sublimate. Until white smoke appears in the funnel and there is white needle crystal on the filter paper, stop heating, naturally cool to 100 C. Remove the funnel, gently peel off the filter paper, and use a spatula to gently scrape the crystal on the filter paper Next mix the residue, use a higher temperature to Sublimation device sublimations should be combined and weighed.two sublimate again. The collected caffeine ofUse a piece of filter paper with many small holes to cover and seal the evaporating dish , and cover a suitable funnel on it to set up the sublimation device. Heat to sublimate. Until white smoke appears in the funnel and there is white needle crystal on the filter paper, stop heating, naturally cool to 100 °C. Remove the funnel, gently peel off the filter paper, and use a spatula to gently scrape the crystal on the filter paper. Next mix the residue, use a higher temperature to sublimate again. The collected caffeine of two sublimations should be combined and weighed. Experimental section Sublimation device