Visual colorimetry defined

The L a b color space is a visually uniform color space and is quite useful for designing devices suitable for visual colorimetry. The angle originating from the positive direction of the a axis expresses the hues themselves and is defined as the hue angle, hab, expressed by Eq. 29 [13] ... 

Colorimetry/photometry exploits the fact that the color intensity of the complex correlates to the metal ion concentration, at least within a certain concentration range. Therefore, sufficient indicator is added to the sample that the indicator forms a colored complex with all ions of the metal of interest in solution. The color intensity of this complex is then either compared visually against the color of reference samples (colorimetry) or the color intensity is measured at a defined wavelength with an instrument and then compared with a calibration curve (photometry). 

Colorimetry—An analytical method by which the amount of a compound in solution can be determined by measuring the strength of its color by either visual or photometric methods. Combustible— Term used to classify certain liquids that will burn on the basis of flash point NEPA and DOT classify combustible liquids as having a flash point of 100°F (38°C) or higher. Combustible liquids—OSHA defines combustible liquids as any liquid having a flash point at or above 100°E (38°C) but below 200°E (93.3°C). 

Beside visual assessment, the color of an object can be characterized more precisely in terms of mathematical models, which are based on the remission and transmission spectra in the visible light area [6]. The most common CIELAB system, defines a color space and allows one to describe a specific color in terms of L (lightness) and the color coordinates a and b, and color differences or tolerances by related AL, A Ab and a combined AE value. L, a, b, values can be transformed into the probably more convenient terms of L (lightness), h (hue) and c (chroma). Today, colorimetry software is used for color matching and allows very precise calculations of pigment formulations. 

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