# Questions On The Quantification Of Light Absorption And Transmittance As A Function Of A Solution

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Quantification of 〖Cr〗^(3+) and 〖Co〗^(2+)in a Mixture
Natalia Nole
Last updated: September 12, 2016
Purpose
Let’s assume that we have two solutions, a clear and a colored one, whose concentrations and identities are unknown. If we shine some light of some intensity towards them; some of this light will go through and some of it will be absorbed. This is important because based on the amount of light absorbed by the solutions we can calculate their concentrations. This important and simple principle is known as Beer’s Lambert law; which states that the absorbance is proportional to the product of the path length, the molar absorptivity and the concentration of a solution. The product of molar absorptivity times path length gives the value of K, which is the slope. (Equation below)
A = Ɛ.Ɩ. C
K = Ɛ.Ɩ.
A=K×C
Spectrophotometry is the quantitative measurement of light absorption and transmittance as a function of a wavelength. The instrument used for spectrophotometry is called the spectrophotometer, and the way it works is as follows. Let’s say we have a source of light, which normally is a deuterium lamp. The beam of light projected by the bulb will hit the diffraction gradient, which looks like a prism. Diffraction gradient will adjust so that only a specific wavelength will make it through an exit slit that eventually hits the sample, whose identity and concentration is unknown. Light absorbed and/or transmitted by the sample will be sensed by the detector which will be