Composition of atmospheric air

Note In the composition of atmospheric air the relative humidity (RH) is indicated separately along with the temperature. ... 

Gay-Lussac and Humboldt used Volta s method (see Vol. Ill, p. 327) of explosion with hydrogen in a eudiometer to determine the composition of atmospheric air. In a number of experiments they found as a mean that 100 vols. of oxygen combined with 199-89 vols. of hydrogen, or in round munbers, that 100 of oxygen require for saturation 200 of hydrogen . The whole-... 

His most Important work was on the composition of atmospheric air and the preparation of oxygen, which he achieved before Priestley. Scheele prepared a number of highly toxic compounds, and his early death may have been due to his experiments with substances such as hydrogen cyanide. 

In processes involving the combustion of fuels, either pure oxygen or air is supplied in amounts greater than the stoichiometric requirements for complete combustion. The terms "theoretical air or theoretical oxygen are thus frequently encountered in combustion problems. The molar composition of dry air at atmospheric conditions [from International Critical Tables, Volume 1, p. 393 (1926)] ... 

The density of the atmosphere varies greatly from place to place, as does its composition and temperature. The average composition of dry air (air from which water vapor has been removed) is shown in Table 4.4. One reason for the nonuniformity of air is the effect of solar radiation, which causes different chemical reactions at different altitudes. The density of air also varies with altitude. For example, the air outside an airplane cruising at 10 km is only 25% as dense as air at sea level. 

It is remarkable that, except for local hot-spots such as around industrial sites, mining areas and volcanoes, the elemental compositions of atmospheric dust in similar locations, such as remote or rural or urban are relatively constant over the world. This suggests either common sources, or a dominant source, or good mixing and transport of the dust around the globe. In fact all three factors have a role in determining the uniformity. Because of the consistent composition it is possible to estimate the median concentrations of the elements in atmospheric dusts in similar, but widely separated, locations. These estimates are given in columns 2 to 7 in Table n. The concentrations of the elements in the atmospheric dust are expressed as mass per volume of air. For remote locations (columns 2 to 5) the concentrations are in ng m 3, whereas for rural and urban areas (columns 6 and 7) the elemental concentrations are in xg m-3. 

The conclusions regarding the composition of nitric acid drawn by Lavoisier from these experiments was, that "nitric acid is nothing else than nitrous air, combined with almost its own volume of the purest part of atmospheric air, and a considerable quantity of water."... 

The atmosphere is made up of a number of gases and, near the earth s surface, water vapor as well. The pressure exerted by atmospheric air is referenced to sea level. Average atmospheric pressure is 1013 mbar (equivalent to the atmosphere , a unit of measure used earlier). Table VIII in Chapter 9 shows the composition of the standard atmosphere at relative humidity of 50 % and temperature of 20 °C. In terms of vacuum technology the following points should be noted in regard to the composition of the air ... 

The pressure of atmospheric air falls with rising altitude above the earth s surface (see Fig. 9.3 in Chapter 9). High vacuum prevails at an altitude of about 100 km and ultrahigh vacuum above 400 km. The composition of the air also changes with the distance to the surface of the earth (see Fig. 9.4 in Chapter 9). 

The Beijing area in north China is well situated for investigating relationships between the elemental composition of atmospheric particulate matter and air mass movements. The municipality of Beijing (Beijing shi) has a population of 7 million, half of whom live in the city proper, and pollution sources of trace gases... 

The papers in this volume were presented at the ACS symposium Chemical Composition of Atmospheric Aerosol Source/Air Quality Relationships sponsored by the Divisions of Nuclear Chemistry and Technology and Environmental Chemistry. This combination reflects the interdisciplinary nature of much of this work which draws from such diverse fields as nuclear chemistry, chemical and mechanical engineering, environmental science and engineering, and applied math. 

This study demonstrates high efficacy and expediency of the TCNQ derivative-based point-contact multistracture as a prospective asset for development of new sensors. The complex character of the sensors response curve and correlation of some response characteristics with different pathological manifestations in human breath, may be further used as a noninvasive diagnostic method alternative to some invasive approaches currently routinely used in clinic. The need for reliable and feasible gas analysis methods functional in presence of atmospheric air, opens opportunities for application of the proposed sensor technique in other spheres of human activity. High sensitivity of the point-contact multistructure enabling analysis of composite gas mixtures, opens up wide possibilities to apply the demonstrated approach for environment and health protection, such as detection of trace amounts... 

Now they see things very differently. The chemical composition of the air is not a precondition for life but the result of it. Around two billion years ago, primitive living organisms transformed the atmosphere from one largely devoid of oxygen to one with plenty... 

POLLUTION (Air). Prior to the Industrial Revolution (circa 1840s). the composition of pure air making up Earth s surrounding atmospheres essentially remained constant for several thousand years. True, certain natural phenomena, such as volcanic eruptions, may have altered the atmospheric composition over relatively short lime spans. 

Troposphere A layer of the atmosphere closest to the Earth which contains about 75% of the mass of the atmosphere. The composition of dry air is relatively constant in this layer of the atmosphere. 

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