Potentiophotometry.

The present derivation relates, in terms of analytical chemical photometry, the theory of operation of an extremely simple instrument which embodies both the electrical analog solution to Beer's Law of Spectrophotometry and the multiplication of this solution by a constant, such that the voltage reading of the instrument is identical to the concentration of the light absorbing substance being measured. Because the raw output of the instrument is both linear and proportionable, calibration of the instrument is accomplished by appropriately setting and positioning the potential difference between two known standard solutions. The determination of the concentration of an unknown solution is then the direct reading of the voltage it generates in the system. This approach to measurement is called Potentiophotometry, because it is based on potentials generated from light.