The subdivision of chemistry concerned with identification of materials (qualitative analysis) and with determination of the percentage composition of mixtures or the constituents of a pure compound (quantitative analysis). The gravimetric and volumetric (or “wet”) methods (precipitation, titration, and solvent extraction) are still used for routine work; indeed, new titration methods have been introduced, e.g., cryoscopic methods, pressure-metric methods (for reactions that produce a gaseous product), redox methods, and use of an F-sensitive electrode. However, faster and more accurate techniques (collectively called instrumental) have been developed in the last few decades. Among these are infrared, ultraviolet, and X-ray spectroscopy, where the presence and amount of a metallic element are indicated by lines in its emission or absorption spectrum; colorimetry, by which the percentage of a substance in solution is determined by the intensity of its color, chromatography of various types, by which the components of a liquid or gaseous mixture are determined by passing it through a column of porous material or on thin layers of finely divided solids, separation of mixtures in ion-exchange columns; and radioactive tracer analysis. Optical and electron microscopy, mass spectrometry, microanalysis, nuclear magnetic resonance (NMR), and nuclear quadrupole resonance (NQR) spectroscopy all fall within the area of analytical chemistry. New and highly sophisticated techniques have been introduced in recent years, in many cases replacing traditional methods.See Spectroscopy; Nuclear Magnetic Resonance; Nuclear Quadrupole Resonance; Chromatography; Fiber, Optical; Supercritical Fluid.
