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Gas mixtures are compressed and homogenised gases that consist of more types of molecules. A main component is referred to a rest gas. The concentration and analytical uncertainty of individual component is specified on the relevant analytical certificate. After filling, the gas mixture is homogenized; after having been homogenized, the gas mixture will no more separate into components, if it is stored by temperature that is higher than the component condensation temperatures.
Calibration gases represent a subgroup of gases with specific demands related to production tolerance, analytical precision, and raw material purity. These gases are mainly applied for calibration of measurement equipment; they also fulfil important tasks in technologies and experimental tests where gas mixtures with a precisely determined composition are required.
Some gas mixtures are produced in the Linde production plant in the Czech Republic; other mixtures are supplied from specialty gas production plants of Linde from other European countries. Gas mixtures production takes between 2 and 14 weeks according to their type and complexity. For users’ convenience, some amount of standard mixtures is always available at Linde Gas plants. Other mixtures are prepared on request.
Calibration gas: mixture of gases, usually compressed, that consists of basic gas and one or more component(s).
Basic gas: pure gas that represents the basic component of the mixture.
Ingredient: calibration gas component in gaseous or steam phase with the specified concentration; it is directly used for testing or calibration.
For the unambiguous gas mixture or calibration gas description, not only the basic gas type and component type have to be specified, but also their concentrations.
Concentration: ratio of the component amount to the total volume of the calibration gas mixture.
For clear concentration definition, the following measuring units are used:
1. Molar fraction = mol/mol
2. Molar concentration in % = molar fraction x 100
3. Volume fraction v/v
4. Volume concentration in % = volume fraction x 100
5. Mass concentration, e.g. kg/m3, g/m3, mg/m3
6. Molar concentration, e.g. mol/m3, mol/l, mmol/l
All this data specification relates to normal conditions (1.013 bar; 273.15 K).
Molar fraction = ideal volume fraction.