A paramagnetic method for measuring the carbon dioxide concentration of a gas

A paramagnetic method of carbon dioxide analysis enables the simultaneous analysis of carbon dioxide and oxygen to be made at 2-min intervals. The method depends upon observing the change of oxygen concentration in a gas mixture before and after absorbing the carbon dioxide component. The carrier-gas in the experiments reported was nitrogen. The output of the paramagnetic meter was measured both by a digital voltmeter and by a chart recorded and the carbon dioxide concentrations calculated from these observations (Y1% and Y2% respectively) were compared with those obtained by Lloyd-Haldane (x%) gas analysis, for carbon dioxide concentration of 2-20% in a range of oxygen concentrations of about 9-90%. The agreement between paramagnetic and Lloyd-Haldane carbon dioxide analysis is shown in the following linear regression equations: Y1=0.996x-0.001 (r=0.9999+/-0.04 SEM of estimate; P less than 0.001); Y2=0.997x-0.006 (r=0.9999+/-0.06 SEM of estimate; P less than 0.001). Carbon dioxide in nitrogen was measured by the prior addition of an arbitrary concentration of oxygen, to a gas sample. The method is applicable to the measurement of carbon dioxide and oxygen, when the carrier-gas may have characteristics which preclude the use of katharometer, infra-red or Haldane analysis.