Gas burette
The gas burette is used to measure gases and, in gas analysis, for the quantitative analysis of gas mixtures . Today, however, this method is meaningless, since gas mixtures can be examined more precisely and elegantly with the help of gas chromatography . In addition, the glass burette has been replaced by the piston syringe in many areas .
functionality
The gas burette consists of a scaled glass tube (e.g. 100 ml) which is provided with a stopcock at the top and bottom. At the bottom the burette is connected to a compensation vessel or level tube. This arrangement is filled with a sealing liquid (e.g. NaCl solution). A measured volume of gas (e.g. 100 ml) is poured into the burette via the upper stopcock, whereby the sealing liquid is pressed into the equalization vessel. Then the gas mixture is also pressed via the upper tap into an absorber vessel with an absorber liquid which absorbs a certain gas from the gas mixture. After absorption , the remaining gas is drawn back into the burette and the volume read off. The volume fraction of the absorbed gas results from the difference to the original volume.
The arrangement, consisting of a gas burette, equalizing vessel and absorption vessel, was developed by W. Hempel . In practice, several gas burettes and absorber vessels were combined to form a gas analysis apparatus (according to H. Orsat ) ( Orsat apparatus ).
Applications
This method was used to investigate blast furnace top gas, generator gas, coke oven gas and various exhaust gases. The following absorber liquids were used:
- Oxygen determination : alkaline pyrogallol solution or sodium dithionite or sodium hydrogen sulfite solution
- Determination of carbon dioxide : potassium hydroxide
- Determination of carbon monoxide : ammoniacal or hydrochloric acid copper (I) chloride solution
Hydrogen and the light hydrocarbons (e.g. methane ) were determined via fractional oxidation with cupric oxide at different temperatures, with the respective decrease in gas volume (in the case of hydrocarbons after absorption of the carbon dioxide formed with potassium hydroxide) was measured in the gas burette . The nitrogen always remains as a gas residue after removing the other components.
Today the method could still have didactic significance for chemistry lessons or for chemist training, e.g. B. for oxygen determination in air.
literature
- KA Hofmann & UR Hofmann: Inorganische Chemie, Friedrich Vieweg Verlag Braunschweig, 9th edition 1941
- Association of German Ironworkers: Manual for the Ironworks Laboratory Volume 1 , Verlag Stahleisen Düsseldorf 1939, p. 240 ff.
- G. Meyendorf: laboratory equipment and chemicals, Aulis Verlag Cologne 1975, ISBN 3-7614-0285-6