Phenolphthalein indicator: Dissolve 1.0 g phenolphthalein powder in 70 mL of ethanol, add 30 mL of deionized water and mix well.
Add a few drops of phenolphthalein indicator to sample and titrate with 0.6476N NaOH with continuous stirring. Titrate to same light pink endpoint used to standardize solutions. Record mL of NaOH titrated.
Adapted from Method 955.01, 16th edition of the Official Methods of Analysis, Association of Official Agricultural Chemists.