is a method used in both organic chemistry
and analytical chemistry
to determine the elemental
composition (more precisely empirical formula
) of a pure organic compound by combusting the sample under conditions where the resulting combustion products can be quantitatively analyzed. Once the number of moles
of each combustion product has been determined the empirical formula or a partial empirical formula of
the original compound can be calculated.
The method was invented by Joseph Louis Gay-Lussac
. Justus von Liebig
studied the method while working with
Gay-Lussac between 1822 and 1824 and improved the method in the following years to a level that it could used as standard procedure for organic analysis.
A combustion train
is an analytical tool for the determination of elemental composition
of a chemical compound
. With knowledge of elemental composition a chemical formula
can be derived. The combustion train allows the determination of carbon
in a succession of steps:
Analytical determination of the amounts of water and carbon dioxide produced from a known amount of sample gives the empirical formula. For every hydrogen atom in the compound 1/2 equivalent of water is produced, and for every carbon atom in the compound 1 equivalent of carbon dioxide is produced.
Nowadays, modern instruments are sufficiently automated to be able to do these analyses routinely. Samples required are also extremely small — 3 mg of sample is sufficient to give satisfactory CHN analysis.