During cryogenic vacuum extraction, a vessel containing soil is connected to an empty vessel. By creating a vacuum, the gas is extracted from the system. While the vessel with soil is heated, the empty vessel is strongly cooled with liquid nitrogen. The vapor pressure difference of both vessels creates a particle flow from the water vapor of the evaporating soil water to the empty vessel by condensation. The extracted water can then be measured by laser spectroscopy. With the remaining sample, the water content can be calculated.
Cryogenic vacuum extraction - Measurement procedure