In
chemistry
Chemistry is the scientific study of the properties and behavior of matter. It is a physical science within the natural sciences that studies the chemical elements that make up matter and chemical compound, compounds made of atoms, molecules a ...
, a sample's oxygen–argon ratio (or oxygen/argon ratio) is a comparison between the concentrations of
oxygen
Oxygen is a chemical element; it has chemical symbol, symbol O and atomic number 8. It is a member of the chalcogen group (periodic table), group in the periodic table, a highly reactivity (chemistry), reactive nonmetal (chemistry), non ...
(O
2) and the
noble gas
The noble gases (historically the inert gases, sometimes referred to as aerogens) are the members of Group (periodic table), group 18 of the periodic table: helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), radon (Rn) and, in some ...
argon
Argon is a chemical element; it has symbol Ar and atomic number 18. It is in group 18 of the periodic table and is a noble gas. Argon is the third most abundant gas in Earth's atmosphere, at 0.934% (9340 ppmv). It is more than twice as abu ...
(Ar), either in air or dissolved in a liquid such as seawater. The two gases have very similar physical properties such as
solubility
In chemistry, solubility is the ability of a chemical substance, substance, the solute, to form a solution (chemistry), solution with another substance, the solvent. Insolubility is the opposite property, the inability of the solute to form su ...
and
diffusivity
Diffusivity is a rate of diffusion, a measure of the rate at which particles or heat or fluids can spread.
It is measured differently for different mediums.
Diffusivity may refer to:
*Thermal diffusivity, diffusivity of heat
*Diffusivity of mass: ...
, as well as a similar temperature dependence, making them easy to compare.
Applications
Biological activity in seawater
Measurements of
primary productivity
Primary or primaries may refer to:
Arts, entertainment, and media Music Groups and labels
* Primary (band), from Australia
* Primary (musician), hip hop musician and record producer from South Korea
* Primary Music, Israeli record label
Works
* ...
in the ocean can be made using this ratio. The concentration of oxygen dissolved in seawater varies according to biological processes (
photosynthesis
Photosynthesis ( ) is a system of biological processes by which photosynthetic organisms, such as most plants, algae, and cyanobacteria, convert light energy, typically from sunlight, into the chemical energy necessary to fuel their metabo ...
and
respiration
Respiration may refer to:
Biology
* Cellular respiration, the process in which nutrients are converted into useful energy in a cell
** Anaerobic respiration, cellular respiration without oxygen
** Maintenance respiration, the amount of cellul ...
) 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.
This technique was first used by Craig and Hayward (1987) when they separated oxygen supersaturations into a biological and a physical component. This O
2/Ar supersaturation can be defined as
∆(O
2/Ar)=(c(O
2 )/c(Ar)) / (c
sat(O
2)/(c
sat(Ar))) -1
where (∆O
2)/Ar is the difference between O
2 production via photosynthesis and removal via respiration, c is the concentration of dissolved gas and c
sat is the saturated concentration of the gas in water at a specific temperature, salinity and pressure.
Oxygen and argon concentrations can be compared using samples from water systems aboard ships using either a membrane inlet mass spectrometer (MIMS)
or an equilibrator inlet mass spectrometer (EIMS).
The measurements can then be used in conjunction with air-sea gas exchange values to calculate biologically induced air-sea O
2 fluxes and net community production.
Determining leakage rates in sealed packaging
Because oxygen and argon leak through packaging material at different rates, comparing the ratios inside a package can determine if and how quickly air from outside has leaked in.
Manufacturing
The characteristics of steel, in particular the carbon and chromium content, can be controlled by adjusting the oxygen/argon ratio during the manufacturing process.
The oxygen/argon ratio is also important in the creation of thin films used in the manufacture of lithium-ion batteries.
References
{{DEFAULTSORT:Oxygen-argon ratio
Analytical chemistry