Combustion analysis is a technique used by chemists to determine the elemental composition of an unknown substance by burning it in a closed container. It is especially used for substances that contain carbon, hydrogen and oxygen in combination.
To perform combustion analysis, chemists must know the mass of the substance before burning it. This is so that the mass of the products of combustion can be compared to the original total mass. The mass of the combustion productions can then be used to calculate the number of moles of oxygen, hydrogen and carbon in the original mass. A Mole is an exact quantity of atoms, so knowing the number of moles makes it possible to know the chemical formula for the substance.