Gaseous compounds, monitoring

Electrochemical sensors are also used to monitor the emissions from combustion processes. Because the oxidizer for most combustion processes is air, which contains 78% nitrogen, NO. gases are common components of the exhaust and their concentrations must be minimized [398, 399]. In addition, incomplete combustion can result in CO or hydrocarbon gaseous compounds in the exhaust gas, which both represent unconverted chemical energy and are hazardous to the environment. The use of sulfur-containing fuels can lead to the formation of SO gases [400], which have a detrimental impact on the environment, such as promoting acid rain. 

Conductometric Sensors for Monitoring Gaseous Compounds. Introduction. Gaseous com-... 

Other applications of this technique, which can detect gaseous compounds down to the sub-ppm range can be found in the environmental monitoring of laboratories, workshops, storage areas of chemicals, refineries, service stations etc. (survey of the maximum tolerable working place... 

Hundreds of chemical species are present in urban atmospheres. The gaseous air pollutants most commonly monitored are CO, O3, NO2, SO2, and nonmethane volatile organic compounds (NMVOCs), Measurement of specific hydrocarbon compounds is becoming routine in the United States for two reasons (1) their potential role as air toxics and (2) the need for detailed hydrocarbon data for control of urban ozone concentrations. Hydrochloric acid (HCl), ammonia (NH3), and hydrogen fluoride (HF) are occasionally measured. Calibration standards and procedures are available for all of these analytic techniques, ensuring the quality of the analytical results... 

The dehydration, desolvation, or decomposition temperature of a compound can also be evaluated from an examination of discontinuities in the optical properties. These processes are most effectively monitored if the sample is immersed in an oil, since the evolution of gases normally accompanies these transformations. The evolution of gases is evident in the generation of gaseous bubbles from the solids under study. 

The above principles have been employed in the construction of a monitor of gaseous inorganic fluorine and chlorine compounds after absorption of the gases in a solution [13], a monitor of free cyanide [35] (fig. 5.9), and a monitor of sulphate using the reaction of the sulphate with a Pb standard solution and, following the decrease in the Pb concentration, with a Pb ISE [152] (fig. 

Once the inhalation exposure questions have been identified, the specifications for each personal monitor must be determined and the monitor must be validated for the contaminant being measured. Table I, updated from Samet et al. (14), identifies currently available personal monitors, and Table II, taken from an Environmental Protection Agency (EPA) report (15), shows the projected needs in the 1990s. There are a number of opportunities for research on personal monitors Table II indicates that relatively few commercial units are currently available for either particulate or gas-phase species. For compounds such as polycyclic aromatic hydrocarbons (PAHs), a two-stage sampler is required because some PAHs exist simultaneously in the gaseous and particulate phase (16). Consequently, research must be ranked with respect to the significance of the air pollution problem, and the technological developments required to provide reliable samplers must be defined. 

Ferreira, B.S., L. van Keulen, and M.M.M. da Lonseca. 2002. A microporous membrane interface for the monitoring of dissolved gaseous and volatile compounds by on-line mass spectrometry. J. Membr. Sci. 208 49-56. 

A standard method for determining solution kinetics of compounds that evolve gaseous products is to measure the amount of gas given off at constant pressure as a function of the amount of liquid displaced from a volumetric buret. Alternatively, it is possible to monitor the change in pressure at constant volume. Timberlake and Martin (125) have described an apparatus that... 

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