Basic terms and concepts in vacuum technology

Absolute pressure is always specified in vacuum technology so that the abs index can normally be omitted. 

The total pressure in a vessel is the sum of the partial pressures for all the gases and vapors within the vessel. 

The partial pressure of a certain gas or vapor is the pressure w/hich that gas or vapor would exert if it alone were present in the vessel. 

Important note Particularly in rough vacuum technology, partial pressure in a mix of gas and vapor is often understood to be the sum of the partial pressures for all the non-condensable components present in the mix - in case of the partial ultimate pressure at a rotary vane pump, for example. 

The pressure of the saturated vapor is referred to as saturation vapor pressure Pg. Pg will be a function of temperature for any given substance. 

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