Last Update: September 25, 2007
Standardization of Strong Bases
Dry primary-standard potassium hydrogen phthalate (KHP) for 2 hr at 110 °C and cool to room temperature in a desiccator. Weigh out samples of 0.7 to 0.8 g measured to the nearest 0.1 mg. To each individual sample in an Erlenmeyer flask add 50 to 75 mL of distilled water to dissolve the KHP and 2 drops of phenolphthalein. Titrate with the strong base until a faint pink color persists for 30 sec.
Standardization of Strong Acids
Dry primary-standard grade anhydrous Na2CO3 for 2 hr at 110 °C and cool to room temperature in a desiccator. Weigh out individual samples of 0.20 to 0.25 g measured to the nearest 0.1 mg. Place a sample in an Erlenmeyer flask and dissolve the Na2CO3 in about 50 mL of distilled water. Add 3 drops of bromocresol green and titrate with the strong acid until the solution just begins to turn from blue to green. Boil the solution for about 3 min and cool to room temperature (the color should change back to blue as the CO2 is removed from the solution; if it does not one can either back titrate with a standard strong base solution, or one must discard the sample). Complete the titration.
1. Skoog, D. A.; West, D. M. and Holler, F. J. Fundamentals of Analytical Chemistry, 5th Ed.; Saunders College Publishing: New York, 1988; p. 767-769.