# colorimetry

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Related to Colourimetry: spectrophotometry, colorimetry

## colorimetry

[‚kəl·ə′rim·ə·trē]
(optics)
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.

## Colorimetry

(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.

## colorimetry

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 ?
Notwithstanding the increasing absolute difference between ICP and colourimetry as soil P increases, the relative difference between the 2 analytical methods was greatest in soils with lower amounts of available P.
With a specific focus on digitally replicating the dynamic range and colourimetry of film, ARRI developed the Alexa camera, which enables HDR delivery by undertaking an HDR colour grade of the original ARRIRAW or Log C material.
Phosphorus was determined following nitric perchloric acid digestion using colourimetry.
The acid extracts were analysed for Al and Fe by atomic absorption spectrometry (AAS), whereas Si was quantified in the alkaline extracts by colourimetry (EMBRAPA 1997).
Ammonium and nitrate concentrations in extract were measured by the indophenol-blue and phenol disulfonic acid colourimetry (Wang et al.
60]) in both the presence and absence of L-TRP was determined by colourimetry.
Inorganic P in each fraction was determined following neutralisation and automated molybdate colourimetry (Turner and Romero 2009).
Water-soluble sulfate was determined turbidimetrically using flow injection analysis colourimetry (Lachat QuickChem 8000).
Samples were filtered through Whatman 41 papers and subsamples taken for analysis of inorganic P, organic P, and total P by molybdate colourimetry (Tiessen and Moir 1993).

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