Infrared gas analysis

Bohnenkamp and Engell and Caplan et have also reported rapid carbon loss from the steel during the initial stage of oxidation at higher temperatures (circa 850°C) followed by a much lower, or zero, loss of carbon later. Caplan et at. measured the COj evolution by infrared gas analysis and reported that the percentage of carbon loss from 0.1 %C, 0.4%C, 0.8%C and 1.2%C steels was overall very small and may be redistributed in the metal. There was no carbon loss detected at 700°C. The overall oxidation rates were all found to be parabolic at 850°C and less than the oxidation rate of pure Fe. In the Fe-C alloys the individual phases of FeO, FejO and... 

Pongracic S., Kirschbaum M. U. F., and Raison R. J. (1997) Comparison of soda lime and infrared gas analysis techniques for in situ measurement of forest soil respiration. Can. J. Forest Res. 27(11), 1890-1895. 

There is not too much argument about analysis methods of the collected particulate material. While a few workers continue to use wet oxidation methods, it is acknowledged that these methods are neither as sensitive nor as accurate as the various dry combustion methods. Most of the more recent work has been done with one or another of the commercially available carbon analyzers (2). However, a few laboratories still use units assembled before the advent of suitable commercial xmits (3). All of these units, commercial or home-built, oxidize the organic carbon to carbon dioxide at high temperatures and measure this carbon dioxide usually by nondispersive infrared gas analysis (4) or by thermal conductivity. The results of the various methods seem completely comparable (5). 

Hill and Powell (1968) have recently written a comprehensive text on non-dispersive infrared gas analysis. They have discussed applications and sampling techniques in science, medicine, and industry instrumentation and detecting systems and methods for producing calibration gas and vapor mixtures. 

Using differential infrared gas analysis for measurements of carbon dioxide exchange (grams of C02/cm /sec), Troughton and Cowan (1968) have observed anomalous depressions in carbon dioxide exchange in cotton leaves that were exhibiting oscillations in transpiration under controlled conditions of environment. 

Gas Exchange. CO2 assimilation and transpiration were measured using an open, flow-through apparatus and infrared gas analysis. Distilled H2O was continuously provided to the entire cut edge of the leaf disc enclosed in a Leaf Section Chamber (Analytical Development Co., Hoddesdon, U.K.). The vapor pressure deficit was maintained at 8.9 1.0 or 18.4 1.0 mbars. This corresponds to relative humidity levels of 72% and 42%, respectively. 

Ethylene Release Ethylene release froM excised leaf discs during incubation in sealed flasks was quantified by gas chroMatography. The COx content of the flask headspace was Maintained by inclusion of a centrewell containing filter paper and sodiuM bicarbonate in phosphate buffer. The 00 level was varied by changing the buffer pH and the bicarbonate concentration (9). Headspace (X3 levels were Monitored by infrared gas analysis. 

Another important application of infrared gas analysis is for trace analysis, such as for the analysis of a dilute mixture (in the ppm range) or an environmental specimen. In such cases, individual analytes are measured from the high ppb levels to the lO s or lOO s of ppm. For such analyses, extended path lengths are required, and typically multipass gas cells from 1 to 20 m in path length are used. One very specific application is an open-path measurement for ambient air monitoring in manufacturing plants or in toxic waste sites in which no cell is used. Instead, a source and interferometer combination are focused on a remote detection system with the aid of special telescope optics. In such cases, several hundreds of meters of effective path length are used. 

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