The HPVA II Series of adsorption analyzers from Particulate Systems uses the static volumetric method to obtain high-pressure adsorption and desorption isotherms utilizing gases such as hydrogen, methane, and carbon dioxide.
The volumetric technique consists of introducing (dosing) a known amount of gas (adsorptive) into the chamber containing the sample to be analyzed. When the sample reaches equilibrium with the adsorbate gas, the final equilibrium pressure is recorded. These data are then used to calculate the quantity of gas adsorbed by the sample.
This process is repeated at given pressure intervals until the maximum preselected pressure is reached. Then the pressure can be decreased to provide a desorption isotherm. Each of the resulting equilibrium points (volume adsorbed and equilibrium pressure) is plotted to provide an isotherm.
Excellent reproducibility and accuracy are obtained by using separate transducers for monitoring low and high pressures.