Some compounds have very high boiling points. To bring such compounds to a boil, it is better to reduce the pressure at which they boil than to increase the temperature. As soon as the pressure is reduced to the vapor pressure of the compound (at a certain temperature), the compound begins to boil and distillation can proceed. The technique is called vacuum distillation and is commonly used in laboratories in the form of vacuum vaporizers. This technique is useful for compounds whose boiling point at atmospheric pressure exceeds their decomposition temperature, and any attempt to boil such compounds at atmospheric pressure causes them to decompose.
1. When installing the vacuum distillation instrument, it is necessary to choose the appropriate size of rubber plug, it is better to choose the grinding mouth vacuum distillation device.
2. The distillate contains a large number of low boiling point substances, need to be distilled under atmospheric pressure first, so that most of the anti evaporation, and then use the pump decompression distillation, so that the low boiling point in addition.
3. Stop heating, recover the low-boiling substance, check the connection of each part of the instrument, and make it close.
4. Start the oil pump, then slowly close the safety valve, and observe whether the pressure on the manometer reaches the requirements, if not, can be adjusted by the safety valve.
5. When the pressure reaches a constant in line with the requirements, then begin to heat the distillation bottle, distillation monomer, should be added in the distillation bottle a little zeolite (generally use oil bath, the temperature is higher than the distillation liquid boiling point of 20 ~ 30 DEG C, difficult to volatilize high boiling point in the later stage can be high 30 ~ 50 DEG C). 6. At the end of distillation, first remove the heat source, to be a little colder, and then gradually open the safety piston, such as pressure gauge mercury column balance drops, stop pumping, such as the system internal and external pressure balance, remove the instrument, rinse.