When monochromatic light passes through a solution of the same thickness and a small concentration, according to Lambert-Beer's law, the extent to which light is absorbed by the solution is called absorbance, which is proportional to the concentration of the solution and proportional to the thickness of the solution, ie A = εCL, where A is the absorbance, C is the concentration of the solution, L is the thickness of the solution, and ε is the extinction coefficient.
According to Lambert-Beer's law, when a bundle of monochromatic light passes through a solution, the intensity of the light is attenuated because the solution absorbs a portion of the light energy. If the concentration (or thickness) of the solution is constant, then the larger the thickness (concentration) of the solution, the more obvious the weakening of the light intensity.
There are two commonly used colorimetric methods: visual colorimetry and photoelectric colorimetry. The former is observed with the eye and the latter is measured with a photoelectric colorimeter
. Both methods are based on Lambert-Beer law (see UV-visible spectrophotometry
Principle of Colorimeter
Being widely used in plastics and printing industries, it is mainly based on the Lab, Lch principle of CIE color space, measuring the color difference △E and △Lab of the sample and the sample to be tested
Correlated analysis method
△E total color difference
△L+ means partial white, △L- means partial black
△a+ means reddish, △a- means greenish
△b+ means yellowish, △b- means bluish
The Lovibond colorimeter is often mistakenly called a colorimeter. Although these two test instruments do have a lot in common, that is, in terms of basic functions. But in fact, the two have different working principles. The Lovibond colorimeter is used to perform colorimetric analysis to determine the amount of known material from color, in a specific reagent yield.