2 Background introduction Caffeine is a derivative of purine, which is weakly alkaline and has the effects of stimulating the heart, exciting the brain and diuresis Pure caffeine is white needle crystal, tastes bitter, and it is soluble in water ethanol. dichloromethane The melting point of caffeine is 238C When the caffeine containing crystal water is heated to 100 C, the crystal water is going to lose and sublimation will begin. The sublimation will be more remarkable at 120C, and if the temperature is 178C or higher, the sublimation process will be very fast CH C N O”N CH Caffeine purine (3,7-Dihydro-1, 3, 7-trimethyl-1-H-purine-2, 6-dione.• Caffeine is a derivative of purine，which is weakly alkaline and has the effects of stimulating the heart, exciting the brain and diuresis. • Pure caffeine is white needle crystal , tastes bitter, and it is soluble in water, ethanol, dichloromethane. • The melting point of caffeine is 238℃: When the caffeine containing crystal water is heated to 100 ℃, the crystal water is going to lose and sublimation will begin. The sublimation will be more remarkable at 120 ℃, and if the temperature is 178 ℃ or higher, the sublimation process will be very fast. purine Caffeine (3,7-Dihydro-1,3,7-trimethyl-1-H-purine-2,6-dione) Background introduction