Gas collecting pipe

The terms gas collection tube , double tap tube and gas mouse describe an elongated gas-tight container with a valve at each end. Usually such a container has a calibrated volume , a cylindrical shape and is made of glass . Gas collection tubes are commonly used for scientific purposes to collect gas samples.

Executions

• Gas collecting tubes made of glass, cylindrical, with two olives
• As before, but with two glass taps, without a partition
• as before, with partition
• as above, but with PTFE taps, without partition
• as before, with partition

Gas collection tubes are available with a capacity of 150, 250, 350, 500 and 1000 ml.

Application: A method for measuring the mass density of a gas

The mass density of a gas can be determined with the following devices: a gas collecting pipe, a laboratory balance and a water jet pump .

The mass and volume of a extracted amount of gas are determined: The gas to be examined is filled into the gas collecting tube at atmospheric pressure and the total mass is then determined. The water jet pump then sucks a large part of the gas out of the gas collecting pipe, and the resulting total mass is also measured. The difference between the two measured values ​​gives the mass of the extracted gas. Finally, the almost evacuated gas collecting pipe is enabled to suck up an outgassed liquid (usually water that has been heated beforehand). This is done again under atmospheric pressure . The last time the now completely filled with liquid gas collection pipe is weighed: . The mass difference of the almost evacuated pipe and the liquid-filled gas collecting pipe gives the mass of the sucked in liquid, which has taken the place of the sucked off gas. The given mass density of the liquid makes it possible to calculate the displaced volume . ${\displaystyle p}$ ${\displaystyle m_{voll}}$ ${\displaystyle m_{gesaugt}}$ ${\displaystyle m=m_{voll}-m_{gesaugt}}$ ${\displaystyle p}$ ${\displaystyle m_{mitProbe}}$ ${\displaystyle m_{Probe}=m_{mitProbe}-m_{gesaugt}}$ ${\displaystyle \rho _{Probe}}$ ${\displaystyle \textstyle V={\frac {m_{Probe}}{\rho _{Probe}}}}$

As a result, the mass and the volume of the extracted gas quantity are available, which makes the mass density calculable under atmospheric pressure. If the gas is a pure substance , then the equation of state allows to determine the molar mass of the gaseous chemical substance: ( represents the universal gas constant ; the absolute temperature at which the measurements were carried out). ${\displaystyle m}$ ${\displaystyle V}$ ${\displaystyle \textstyle \rho ={\frac {m}{V}}}$ ${\displaystyle M}$ ${\displaystyle \textstyle M={\frac {m\cdot R\cdot T}{p\cdot V}}\,}$ ${\displaystyle R}$ ${\displaystyle T}$

See also

• Laboratory equipment

Individual evidence

1. ↑ Physical chemistry, Kaiser, Hennig, Verlag Dr. Max Gehlen, Bad Homburg, 1983, page 140