Vapor Pressure Analyzer

The Vapor Pressure Analyzer, or VPA, measures the vapor pressures of solids, liquids and oils using the Knudsen effusion method.

The vapor pressure is an important material physical property that defines the amount of vapor phase material that exists in equilibrium with the original material. All materials enter the vapor phase by sublimation (solid – gas) or evaporation (liquid – gas). The vapor pressure of a material at thermodynamic equilibrium is a fundamental property of the material and is only a function of temperature.

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Knudsen Method
The Knudsen effusion method is a dynamic gravimetric technique based on the rate of escape of vapor molecules through an orifice of known dimensions in a Knudsen cell into a vacuum at a known temperature. The rate of mass loss through the orifice is measured by the Surface Measurement Systems’ UltraBalance within the VPA system. Sample masses from 1 to 100mg can be studied typically in the temperature range from 20 to 400 °C.

Temperature-controlled incubator
The incubator provides a controlled and stable temperature environment for experiments.
Range: 20 °C to 85 °C
Stability: ±0.2 °C (20 °C to 85 °C)High-temperature pre-heater
The local sample pre-heater heats the sample up to 400 °C.

Vacuum system
Rotary pump can produce minimum vacuum pressure of 1 x10-3 Torr.
Turbomolecular pump in combination with rotary pump provides lower vacuum pressure down to 1x 10-7 Torr.

Vacuum Gauge
Ultimate vacuum pressure is measured using vacuum transducer operating in the range from 900 to 1×10-8 Torr.

Vacuum manifold
Constructed primarily of 316 stainless steel for chemical inertness, KF flanges
and VCR sealed (Cu) fittings

Ultra microbalance
Measures the sample mass in real time at a given temperature and high vacuum.
Sample mass: up to 1.0g
Mass change: up to ±150mg
Resolution (precision): 0.01 μg
Peak to peak noise: ≤ 0.7 μg

Vapor Pressure Analyzer Schematic

Vapor Pressure Analyzer Schematic