Derive an equation that relates the pH to the ratio of the acidic and basic indicator forms assuming that the absorption band of these forms overlaps partially and the total absorbance measured at...

Derive an equation that relates the pH to the ratio of the acidic and basic indicator forms assuming that the absorption band of these forms overlaps partially and the total absorbance measured at each wavelength is the sum of the absorbances of each form. What advantages brings about this transduction scheme? Hint: use Equation (19.3) as starting point