Colorimetry, as the name suggests, means the measurement of colors. In terms of chemical analysis, it is, more specifically, the measurement of the concentration of a particular compound (solute) in a colored solution (solvent). During scientific work, we often need to measure quantities of a particular compound in a mixture or the concentration of the solution. The trick is to identify the difference in colors of various mixtures and ascertain their absolute values. This is more informative and scientifically useful than simply having subjective judgments such as solutions being light or dark in color.[1]
Our eyes are not good enough to distinguish finer differences in colored solutions!
Light in the form of electromagnetic radiation enables a human eye to visualize objects. Visible light is measured in terms of wavelengths in the range of 400-700nm.[1][2] Scientists have identified that the human eyes have 3 different types of cone cells which helps perceive color. This phenomenon is called Trichromacy.[3] In order to create different colors, a human eye needs three different wavelengths of light; blue (short range), green (medium range), and red (long range).[4] There is a threshold beyond which the human eyes are not sensitive enough to distinguish small changes in the colors of a solution. Therefore, there is a need for a more sensitive measuring instrument which could give reliable and consistent results. This instrument is known as a Colorimeter. In determining the concentration of a solute in a solution, the Beer-Lambert law is used.
The first criterion for measuring the amount of solute in a given solvent is that the solution must be homogeneous. When a rayd
