Dry distillation
Dry distillation involves heating in the absence of oxygen and heat is
applied usually as a direct flame to the vessel. The high temperatures
release essential oils. And the steams of essential oil are condensed to
produce essential oil, this process may lead to pyrolysis in the solid.
In extraction dry distillation, many organic compounds may decompose.
This method is used to extract essential oils with a high boiling point
from wood or coal [20].