SE372100

1,265,348. Electro-chemical analysis. PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd. Nov. 14, 1969 [Nov. 19, 1968], No. 55848/69. Heading G1N. In a system for electro-chemical monitoring of constituents in a flowing fluid, (e.g. SO 2 in air), provision is made for frequent ZERO SETTING with the CARRIER ONLY flowing, and CALIBRATION with the addition of a KNOWN QUANTITY of the constituent. As shown, a motor driven 3-way cock 7, diverts air through a SO 2 -absorbing filter 6 to set the zero of test cell 9 with only the carrier flowing via passage 1, 3. Then the carrier is directed through passage 1, 4 to pick up a known quantity of SO 2 from absorption cell 8, before reaching the measuring cell 9, and finally air flows directly through passage 2, 3 for measurements. Air is sucked through the monitor at a constant rate by vacuum-pump 25 with capillary constrictions 23, 24 in the suction lines. Inlet filters such as a gauze particle strainer 17, and dust filter 18 may be provided together with an absorber 21 for ozone, hydrogen sulphide, and chlorine, which would interfere with the measurements. An absorption cell with a semi-permeable membrane connection to the SO 2 calibration source is described, Fig. 5 (not shown). Modifications. A multiposition cock may be used, Figs. 2, 4 (not shown) providing a plurality of passages 1-4, selectively connecting to a plurality of series arranged absorption cells, to provide several levels of concentration of SO 2 for calibration.