Continuous analysis of auto exhaust by infrared spectrophotometer

Studies on the Auto Exhaust Analysis. I

Abstract

Infrared spectrophotometric method of analysis of auto exhaust has been studied in order to perform a continuous determinations of carbon monoxide, carbon dioxide, and hydrocarbons in accordance with the changes of the driving modes of automobiles. A small volume cell of 10 cm light path and a continuous recording-scale expansion attachment were used so that the continuous, high response, and sensitive measurement at a given wavelength might be possible. Sample gas was introduced into the cell after drying by passing through the condenser, the filter, and the desiccant. The pressure in the cell was always maintained at an atmospheric pressure by using an automatic pressure control valve at the inlet of the cell. Absorption peaks at 4.6 and 2.7 μ were used for the determinations of carbon monoxide and carbon dioxide, respectively. Although the exhaust gas contains more than several tens of hydrocarbons, most of them give an absorption peak at 3.4 μ. Hydrocarbons were, therefore, determined at 3.4 μ by calibrating with n-hexane for convenience. The ranges of measurement are 0.115% for carbon monoxide, 0.316% for carbon dioxide, and 504000 ppm as n-hexane for hydrocarbons. The recorder indication up to 95% of equilibrium takes about 2 sec. Methane and ethylene could also be determined by the present method.