Abstract: Ozone generated for chemiluminescent reaction in an analyzer for the measurement of oxides of nitrogen, for example, is purified by passing the ozone through a bed of silica gel, thereby removing substances that interfere with the analysis.

Abstract: Hydrogen sulfide scrubber for use with sulfur compound analyzers effectively removes hydrogen sulfide from gas streams, such as ambient air, without removing substantial amounts of other sulfur compounds, particularly sulfur dioxide. The scrubber employs a bed of silver sulfate, silver nitrate, or silver iodide and operates effectively over wide temperature and humidity ranges without requiring temperature control, with minimal interference from ozone, and operates at flow rates employed by conventional sulfur analyzers without excessive pressure drops.

Abstract: A catalytic converter comprises a block having a bore receiving a tube coaxially, the tube being suspended in the bore by a fitting threaded into one end of the bore and being spaced from the wall of the bore so that a gas may flow along the exterior of the tube and then through the interior of the tube. For converting nitrogen dioxide to nitric oxide, the tube contains copper granules held in place by plugs of copper turnings. Temperature control and regulation are also provided.

Abstract: A copper catalyst maintained in the temperature range of 220.degree. to 240.degree.C. is employed to convert nitrogen dioxide to nitric oxide, as in the measurement of oxides of nitrogen by chemiluminescent techniques. The converter comprises a body having a bore receiving a copper tube coaxially, the tube being spaced from the wall of the bore so that a gas containing nitrogen dioxide may flow along the exterior of the tube and then through the interior of the tube, which contains copper granules held in place by plugs of copper turnings. The temperature of the body is maintained by heater tape wound about the body, and the body is enclosed within an insulated container.