Gas Eudiometry
The realtionship amongst gases, when thay react with one another, is goverened by two laws, namely Gay-Lussac law and Avagadro's law.
Gaseous reactions for investigation purposes are studied in a closed graduated tube open at one end and the other closed end of which is provided with platinum terminals for the passage of electricity through the mixture of gases. Such a tube is known as Eudiometer tube and hence the name Eudiometry also used for Gas analysis.
During Gas Analysis, its Eudiometer tubed filled with mercury is inverted over a trough containing mercury. A known volume of the gas or gaseous mixture to be studied is next introduced, which displaces an equivalent amount of mercury.
The following reactions among gases can be drawn:

    
Volume-Volume relationship amongst gases or simple Gaseous reactions.


    
Composition of Gaseous mixtures.


    
Molecular formulae of gases


    
Molecular formulae of Gaseous Hydrocarbons

The various reagents used for absorbing different gases are
O3 → turpentine oil
O2 → alkaline pyrogallol
NO → FeSO4 Sol.


CO2, SO2 → alkali Sol. (NaOH, KOH, Ca(OH)2, HOCH2CH2NH2, etc.)


NH3 → acid Sol. or CuSO4 Sol.


Cl2 → water