Signals and signal calibration

The area under the desorption peak and the area under the calibration peak A are used to calculate the volume desorbed from the sample according to equation (15.8) 

Equation (15.8) requires no correction for ideality since the volume desorbed is measured at ambient temperature and pressure. Because desorption occurs at room temperature it is complete and represents 

Sample cells are not completely filled with powder room is left above the surface for the unimpeded flow of gas. Although the gas flows over the powder bed and not through it, lower flow rates aid to ensure against elutriation. 

The areas under the adsorption and desorption peaks are usually not exactly the same. This is due to the changing slope of Fig. 15.6. Adsorption produces concentration changes to the right or in the direction of decreased sensitivity, while desorption produces signals in the direction of increased sensitivity. 

The signals must propagate through the system at identical flow rates. 

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