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Related to Colourimetry: spectrophotometry, colorimetry


Any technique by which an unknown color is evaluated in terms of standard colors; the technique may be visual, photoelectric, or indirect by means of spectrophotometry; used in chemistry and physics.



(1) In analytical chemistry, colorimetry is a group of photometric methods of quantitative analysis based on the determination of the concentration of substances in a colored solution by measuring the amount of light absorbed by the solution. The amount of light absorbed, the thickness of the layer of solution, and the concentration of the solution are related by a formula that obeys the Bouguer-Lambert-Beer law:

(1) I = Io · e-kcl

where I is the intensity of light after passing through the absorbing medium, Io is the intensity of the incident light, l is the thickness of the layer of solution (in cm), c is the concentration of the absorbing substance (in moles per liter), and K is a constant for light of a particular wavelength. After the logarithm is taken, equation (1) takes the form

(2) In (Io/I) = Kcl = D

where D is the optical density of the solution. It follows from equation (2) that D is directly proportional to the concentration of the substance in the solution.

A distinction is made between subjective (visual) and objective (photocolorimetric) methods of colorimetry. In visual methods, the optical density is determined by comparing the color of the solution being studied with the colors of a series of standard solutions, as well as by using visual colorimeters. In objective methods, photoelectric colorimeters are used.

(2) In physics, colorimetry is the methodology of measuring and expressing color in quantitative terms, and also the set of such methods.


The science of measuring color. The International Commission on Illumination (Commission Internationale de l'Eclairage) governs this subject along with all aspects of lighting and illumination. See CIE Lab and colorimeter.
References in periodicals archive ?
Phosphorus functional groups were expressed as a percentage of total signal area and concentrations in the NaOH EDTA extracts were calculated on the basis of the total P in the extracts measured by molybdate colourimetry (see above).
4]-N) was determined by indophenol blue colourimetry via flow injection analysis on a Lachat Instruments autoanalyser (NWASCO 1982).
The unfiltered and filtered samples were analysed for total P (TP) and total dissolved P (TDP), respectively, using an acidic persulfate digest (APHA 1995) and subsequent determination of P by colourimetry (Murphy and Riley 1962).
The determination of inorganic P in the NaOH-EDTA soil extracts was based on colourimetry using the molybdenum blue method of Murphy and Riley (1962).
The amount of mineral N measured by colourimetry was close to the measurements performed after distillation of the KCl solution ([R.
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In these studies, samples were analyzed using X-ray fluorescence spectrometry or a combination of a fusion or sintering digestion followed by measurement by colourimetry (e.
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I have a keen interest in the use of colourimetry, having struggled through education myself.