The Concurrent Determination of Sulfur Dioxide and Nitrogen Dioxide in the Atmosphere

Concurrent determinations of low concentrations of sulfur dioxide by the conductimetric and fuchsin methods; and of nitrogen dioxide by the Saltzman method, by means of 3 suitably adapted Automatic Impingers at a common atmospheric sampling point in Windsor, Ontario. Conductimetric determinations yielded consistently higher values for sulfur dioxide than the colorimetric method based on the chromogenic reaction of fuchsin, formaldehyde and sulfite. The nitrogen dioxide levels fluctuate similarly to sulfur dioxide and are somewhat lower than the conductimetric sulfur dioxide levels. When the fuchsin values are corrected for the effect of nitrogen dioxide, the colorimetric sulfur dioxide levels are in fairly close agreement with those estimated by the conductimetric method. Data show the hourly variation in Windsor are lower than in Los Angeles.