ABSTRACT
Sulfur dioxide absorbs radiation over a broad range of wavelengths which include the infrared and ultraviolet regions of the spectrum. The oxides of sulfur are measured both in ambient air, where their concentration is usually a small fraction of one ppm, and in stack and other industrial emissions, where their concentrations are in hundreds of ppm. Stack effluents contain orders of magnitude higher concentrations of sulfur dioxide then does ambient air. Few of the principles used to detect the trace amounts of sulfur dioxide in ambient air are applicable to source monitoring except by massive dilution. The correlation spectrometer can be used at a location remote from the source to determine the sulfur dioxide content of stack gases. The measurement of sulfur dioxide in air has been performed for many years because of the simplicity of manual analysis based on the ability of sulfur dioxide to reduce a starch-iodine solution.
