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Gas analyzers

instruments for determining the qualities, and quantities, the composition of the mixtures of gases. Distinguish g. manual action and automatic. Among the first are most common absorptive g., in which the components of gas mixture are consecutively by different reagents (see gas analysis). For the complete analysis of multicomponent gas mixture widely they use G. vsesoyuznogo heat-technical institute. Avtoma-tich. G. continuously measure some physics or phys.-chem. characteristic of gas mixture or its section of components. According to the operating principle of avtomatich. G. can be divided into 3 groups: 1) the instruments, based on the physical methods of analysis, which include vspomogat. of chem. reaction. With the aid of such g., NAZ volumetrically mi or by chemical, determines a change in volume or pressure of gas mixture as a result of chem. reactions its section of components.

2) the instruments, based on the physical methods of analysis, which include vspomogat. phys.-chem. processes (thermo-chem., electro-chem., fotokolorimetrich., khromatografich. and other). Thermochemical, based on the measurement of the thermal effect of the reaction of catalytic oxidation (combustion) of gas, use mainly for determining the concentrations of combustible gases (for example, the dangerous concentrations of carbon monoxide in air). Electrochemical make it possible to determine gas concentration in the mixture in terms of the value of the elec. conductivity of the solution, which absorbed this gas. The photocolorimetric, based on the change colors of the specific substances with their reaction with the analyzed component of gas mixture, use mainly for measuring the microconcentrations of toxic admixtures in the gas mixture - hydrogen sulfide, nitrogen oxides and other chromatographic most widely are used for the composite analysis of the gaseous hydrocarbons (see also chromatography, chromatographs).

3) the instruments, based on the purely physical methods of analysis (termokonduktometrich., densimetrich., magnetic, optich. and other). Termokonduktometri of cheski e, based on thermal conductivity measurement of gases, make it possible to analyze the two-component mixtures (or multicomponent with the condition changes in the concentration only of one component). With the aid of densimetrich e -skix g., based on density measurement of gas mixture, is determined mainly the carbon-dioxide content, whose the density 1,5 times exceeds the density of pure air. Magnetic g. use mainly for determining the concentration of oxygen, which possesses large magnetic susceptibility. Optich. G. are based on the measurement of optical density, spectra of absorption or emission spectra gas mixture. The content in the gas mixture of halogens is determined with the aid of ultraviolet g., it is mercury vapor, some organic connections. On the field of applications of g. see in st. Gas analysis.

Lit.: Sokolov V. A., the methods of the analysis of gases, M., 1958; Pavlenko V. A., Gas analyzers, M. - L., 1965.

In. V. krasnoshchekoye.