GB707914A - Method and apparatus for measuring the oxygen content in gaseous mixtures - Google Patents

Abstract

Apparatus for determining the quantity of oxygen in a gaseous mixture comprises means for exposing a known quantity of the gas to phosphorus and mixing the resulting gases with a measured volume of water, thereby producing phosphoric acid solution whose concentration, which is a measure of the original oxygen content, can be determined by measuring the conductivity of the solution. In an intermittently-operating system (Fig. 1) the water is supplied at a constant head from a tank 3 through a hydrogen-ion exchange unit 7 where the hardness is corrected and through a conductivity cell 13 into a tank 1 containing sticks of phosphorous. The gas mixture is drawn into the mixing tank 1 through branch pipe 17 via an asbestos filter 22, and bubble bottle 24 by a water aspirator 21. The <PICT:0707914/III/1> <PICT:0707914/III/2> phosphoric acid solution flows out of tank 1 through a syphonoperated overflow pipe 10, through a second conductivity cell 131, and the conductivity of the two cells 13, 131 is compared in a bridge circuit whose unbalance current is indicative of the oxygen content of the gas mixture. A combined mixing tank and conductivity cell for continuous measurement comprises a glass flask 38 (Fig. 4) in which a capillary tube 40 is centrally supported by two sintered glass discs 41, 42, the former acting as support for molten phosphorous. The flask 38 is enclosed in a water tank 44, fed from a constant head supply by inlet 45, the water reaching the inside of flask 38 by capillary inlet 46. The gas mixture enters through tube 40 from a pipe 60, bubbles through the molten phosphorus on disc 41, and escapes through outlet 54 while the acid solution passes through aperture 53 into a conducting chamber containing electrodes 57, 58, another set of electrodes 571, 581 measuring the conductivity of the original water.