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The characterization gas collecting tube describes an oblong gas-tight container with one valve at either end. Usually such a container has a gauged volume, has a cylindrical shape and is made of glass. Gas collecting tubes are used for science-related purposes; for taking samples of gases.
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Capacity of gas collecting tubes 150, 250, 350, 500 and 1.000 ml
The mass density of a gas can be measured by using a gas collecting tube, an analytical balance and an aspirator. The mass and volume of a displaced amount of gas are determined: At atmospheric pressure , the gas collecting tube is filled with the gas to be investigated and the overall mass is measured. Then the aspirator sucks out much of the gas yielding a second overall mass measurement. (The difference of masses represents the mass () of the extracted amount of gas.) Finally, the nearly evacuated gas collecting tube is allowed to suck in an outgassed liquid, usually previously heated water, which is offered under atmospheric pressure . The gas collecting tube is weighed for a third and last time containing the liquid yielding the value . (The difference of masses of the nearly evacuated tube and the liquid-containing tube gives the mass () of the sucked-in liquid, that took the place of the extracted amount of gas.) The given mass-density of the liquid permits to calculate the displaced volume (). Thus giving mass and volume of the extracted amount of gas, consequently accessing its mass density () under atmospheric pressure. [1]
The mass density of a fluid can be measured by using a gas collecting tube, an analytical balance and two other fluids of known mass densities, preferably a gas and a liquid (with mass densities , ). Overview: First, mass measurements get the volume and the evacuated mass of the gas collecting tube; secondly, these two are used to measure and calculate the mass-density of the investigated fluid.
Fill the gas collecting tube with one of those fluids of given mass density and measure the overall mass, do the same with the second one giving the two mass values , . Consequently, for those two fluids, the definition of mass density can be rewritten:
These two equations with two unknowns and can be solved by using elementary algebra:
(The relative error of the result significantly depends on the relative proportions of the given mass densities and the measured masses.)
Now fill the gas collecting tube with the fluid to be investigated. Measure the overall mass to calculate the mass of the fluid inside the tube yielding the desired mass density .
If the gas is a pure gaseous chemical substance (and not a mixture), with the mass density , then using the ideal gas law permits to calculate the molar mass of the gaseous chemical substance:[ citation needed ]
Where represents the universal gas constant, the absolute temperature at which the measurements took place.
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The shear viscosity of a fluid is a material property that describes the friction between internal neighboring fluid surfaces flowing with different fluid velocities. This friction is the effect of (linear) momentum exchange caused by molecules with sufficient energy to move between these fluid sheets due to fluctuations in their motion. The viscosity is not a material constant, but a material property that depends on temperature, pressure, fluid mixture composition, local velocity variations. This functional relationship is described by a mathematical viscosity model called a constitutive equation which is usually far more complex than the defining equation of shear viscosity. One such complicating feature is the relation between the viscosity model for a pure fluid and the model for a fluid mixture which is called mixing rules. When scientists and engineers use new arguments or theories to develop a new viscosity model, instead of improving the reigning model, it may lead to the first model in a new class of models. This article will display one or two representative models for different classes of viscosity models, and these classes are:
