How to deal with the problem that the rotary evaporators cannot be vacuumed

Rotary evaporator is mainly used for continuous distillation of a large number of volatile solvents under reduced pressure Especially for the concentration of extraction liquid and the distillation of receiving liquid in chromatographic separation, the reaction products can be separated and purified The basic principle of rotary evaporator is vacuum distillation, that is, under the condition of vacuum, when solvent distillation, the distillation flask is rotating continuously Structure: the distillation flask is a pear shaped or round bottom flask with a standard grinding port It is connected with the pressure reducing pump through a high reflux serpentine condensate pipe, and another opening of the reflux condensate pipe is connected with the receiving flask with grinding port for receiving the evaporated organic solvent There is a three-way piston between the condensing pipe and the pressure reducing pump When the system is connected with the atmosphere, the distillation flask and the liquid receiving flask can be removed and the solvent can be transferred When the system is connected with the pressure reducing pump, the system should be in the pressure reducing state When using, reduce the pressure first, and then start the motor to rotate the distillation flask At the end, stop the machine first, and then open the atmosphere to prevent the distillation flask from falling off during the rotation As the heat source of distillation, it is often equipped with a corresponding constant temperature water tank (I) use method of rotary evaporimeter: 1 Height adjustment: manual lifting, turning the hand wheel on the column, turning clockwise into ascending, reversing into descending Electric lifting, touch the up key to raise the main engine, and touch the down key to lower the main engine 2 There are two external connectors on the condenser for cooling water, one for water inlet and the other for water outlet, generally for tap water The lower the temperature of the condensate, the better the effect The upper port is equipped with a vacuum connector, which is connected to the vacuum pump skin pipe for vacuum 3 Before starting the machine, first turn the speed control knob left to Zui, press the power switch indicator light, and then slowly turn right to the required speed Generally, medium and low speed solutions with high viscosity are used for large evaporation bottles The flask is No 24 standard interface, with two kinds of flasks of 500ml and 1000ml attached, and the amount of solution is generally not more than 50% (II) precautions for rotary evaporimeter: 1 The glass parts shall be handled with care, cleaned, dried or dried before installation 2 Each grinding port, sealing surface sealing ring and joint shall be coated with a layer of vacuum grease before installation 3 Before the heating tank is powered on, water must be added, and dry burning without water is not allowed 4 Screw in the safety hole to avoid damaging the flask 5 If the vacuum cannot be pumped up, it needs to be checked (1) whether all joints and interfaces are sealed (2) whether the sealing ring and sealing surface are effective (3) whether the vacuum grease between the main shaft and the sealing ring is well coated (4) check whether the vacuum pump and its skin tube leak (5) whether the glass parts are cracked, broken or damaged