Hello, We are setting up the chloroform fumigation-extraction method following the protocol of Vance et al. (1987). According to the method, the chloroform should be boiled under vacuum for 2 minutes. In our case, boiling starts and continues for about 20–30 seconds, but then it stops even though the vacuum is maintained. Has anyone experienced a similar situation? Thank you!
Is boiling perhaps related to removal of some of the decomposition products?
Hello
This is a normal phenomenon. Creating a vacuum lowers the boiling point of the substance, but evaporation also removes heat energy, which lowers the temperature of the surroundings and the substance. This temperature drop stops boiling (the substance only slowly evaporates). To maintain boiling, you need to add some energy, most often through light from a quartz bulb (infrared radiation).
I think you should try gradually increasing the boiling point since you should see if the vapor released by the compound equals the pressure found outside the vacuum, then you should increase the temperature little by little in a constant manner.
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