A three-hour laboratory experiment, designed for an advanced undergraduate course in instrumental analysis that illustrates the application of the gradient chamber flow-injection titration (GCFIT) method with spectrophotometric detection to determine acidity constants is presented. The procedure involves the use of an acid-base indicator to obtain the relation between the pH and the absorbance of the solution throughout the titration which constitutes a new approach to the determination of p[K[subscript a]]'s by GCFIT.