The electric vacuum drying oven , as a basic tool for experimental research, is basically available in every laboratory, and there are certain differences in the use of each lab, summarized in the following ways. 1. The temperature is generally controlled at 50 ~ 60 degrees, phosphorus pentoxide placed in the oven, the oil pump vacuum, vacuum up the pump off, if the vacuum drops during use, open the oil pump and then pump, repeatedly. 2. Do not turn off the oil pump, day and night operation, until the end of drying 3. do not put phosphorus pentoxide in the oven, if the use of the process found in the oven wall attached to water droplets, open the door to wipe to remove until the end of the dry oven 4 Using circulating water vacuum pump, the vacuum degree of water ring pump is limited by the saturated vapor pressure of water, the vacuum degree can only reach 2000-3000Pa.(Oil pump can reach 130Pa). As to whether to use oil pump or water ring pump, it should depend on whether the material