volumetric analysis

volumetric analysis, any method of quantitative chemical analysis in which the amount of a substance is determined by measuring the volume that it occupies or, in broader usage, the volume of a second substance that combines with the first in known proportions, more correctly called titrimetric analysis (see titration).

The first method is exemplified in a procedure devised by a French chemist, Jean-Baptiste-André Dumas, for determining the proportion of nitrogen combined with other elements in organic compounds. A weighed sample of the compound is burned in a furnace under conditions that ensure the conversion of all the nitrogen to elemental nitrogen gas, N₂. The nitrogen is carried from the furnace in a stream of carbon dioxide that is passed into a strong alkali solution, which absorbs the carbon dioxide and allows the nitrogen to accumulate in a graduated tube. The mass of the nitrogen can be calculated from the volume it occupies under known conditions of temperature and pressure, and therefore the proportion of nitrogen in the sample can be determined.

A volumetric method is also applied in the analysis of nitrates, which can be converted into nitric oxide, NO, a gas. Production or consumption of carbon dioxide during biological processes often is measured volumetrically. The composition of fuel gases and combustion products can be determined by measuring the changes in volume that occur when the sample is treated successively with reagents that specifically absorb such components as carbon dioxide, carbon monoxide, oxygen, and others.