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1986
Journal Article
Titel
Gravimetric calibration of standard gases
Abstract
Permeation rates of specific gases (e.g. SO2, NO2) in the range of 10 E-9g min E-1 were directly measured using a high performance microbalance. The gases were trapped in small permeation tubes with total weights of about 2.5 g. By controlling the microbalance's temperature the measurements were done at set temperatures between 25 degrees C and 60 degrees C to obtain a reference graph (permeation rate vs. temperature) for each gas. The microbalance was connected to a metered flow of a clean-air device. With adjustable flow rates up to 50l min E-1 the permeating gas could be diluted down to volume mixing ratios in the 10 E-9 and even the 10 E-12 range. (IFU)