Search results
Results from the WOW.Com Content Network
Argon is used to displace oxygen- and moisture-containing air in packaging material to extend the shelf-lives of the contents (argon has the European food additive code E938). Aerial oxidation, hydrolysis, and other chemical reactions that degrade the products are retarded or prevented entirely.
By mole fraction (i.e., by quantity of molecules), dry air contains 78.08% nitrogen, 20.95% oxygen, 0.93% argon, 0.04% carbon dioxide, and small amounts of other trace gases (see Composition below for more detail). Air also contains a variable amount of water vapor, on average around 1% at sea level, and 0.4% over the entire atmosphere.
Trace gases are gases that are present in small amounts within an environment such as a planet's atmosphere.Trace gases in Earth's atmosphere are gases other than nitrogen (78.1%), oxygen (20.9%), and argon (0.934%) which, in combination, make up 99.934% of its atmosphere (not including water vapor).
An air separation plant separates atmospheric air into its primary components, typically nitrogen and oxygen, and sometimes also argon and other rare inert gases. The most common method for air separation is fractional distillation. Cryogenic air separation units (ASUs) are built to provide nitrogen or oxygen and often co-produce argon.
The standards below are two examples of commonly used and cited publications that provide a composition for standard dry air: ISO TR 29922-2017 provides a definition for standard dry air which specifies an air molar mass of 28,965 46 ± 0,000 17 kg·kmol-1. [2] GPA 2145:2009 is published by the Gas Processors Association.
Purified argon gas is the most commonly used inert gas due to its high natural abundance (78.3% N 2, 1% Ar in air) [3] and low relative cost. Unlike noble gases , an inert gas is not necessarily elemental and is often a compound gas.
The concentration of oxygen dissolved in seawater varies according to biological processes (photosynthesis and respiration) as well as physical processes (air-sea gas exchange, temperature and pressure changes, lateral mixing and vertical diffusion). Argon concentrations, by contrast, vary only by physical processes.
Asphyxiant gases in the breathing air are normally not hazardous. Only where elevated concentrations of asphyxiant gases displace the normal oxygen concentration does a hazard exist. Asphyxiant gases are marked SA in the NFPA 704 standard. Examples of hazards are: Environmental gas displacement