Combination volumes law . Many of the elements and compounds are gaseous, and since it is easier to measure a volume than a weight of natural gas, the volume relationships in which the gases combine are studied.
By obtaining water vapor from the elements it had been found that one volume of oxygen joins two volumes of hydrogen to form two volumes of water vapor; all gaseous volumes measured under the same conditions of pressure and temperature.
This simple relationship between the volumes of these reactive gaseous bodies was not a fortuitous case, since Gay-Lussac showed that it was true in all reactions involving gases.
Lussac formulated in 1808 the Law of the volumes of combination that bears his name, which can be stated as follows: in any chemical reaction the volumes of all the gaseous substances that intervene in it are in a relation of simple integers.
The law does not apply to the relationship between the volumes of reacting solid and liquid bodies such as the volume of sulfur that binds with oxygen to form sulfur dioxide.
Lussac observed that the volume of the resulting gaseous combination was less than or equal to the sum of the volumes of the gaseous substances being combined.