TITRATION OF POLYPROTIC ACIDS Procedure: 1. Measure out a 10.0mL sample. Place the sample in a beaker, and add a few drops of methyl red and phenolphthalein. 2. Begin titrating, by adding NaOH in 0.5mL increments. After adding each 0.5mL allow the solution to mix thoroughly and record the pH. 3. Continue the titration until obtaining a constant pH. 4. Plot pH vs. volume of NaOH