Gauges, effusion

Summary of literature data Spinning rotor fraction gauge Torsion mass loss effusion Static method ... 

Knudsen121 Effusion Gauge. To measure the vapor pressure of solids or liquids indirectly, a Knudsen cell is a cylindrical cell containing the sample. A small opening at the top of the cell allows molecules to evaporate at a fixed rate, proportional to the vapor pressure inside the cell. The mass loss of the cell is proportional to the pressure and is measured after a fixed time, for several temperatures. 

Figure 3.36. Apparatus used by Wiedemann (60) for Knudscn effusion vapor-pressure measurements. A, Knudsen cell B, cold trap C. ionization gauge D. balance and housing E, diffusion pumps F. thermostatically controlled reaction chamber.

In small effusions, the patient is asked to rotate the leg externally to increase filling of the lateral portion of the pouch so it can be easily punctured. For this purpose, a 21 gauge spinal needle is adequate. The knee being a large synovial joint, up to 50 ml can be aspirated from it and/or injected within it... 

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