Quantitatively transfer the dissolved calcium carbonate solution to a 25 mL volumetric flask. Using a water bottle, add DI water to the volumetric flask until the volume reaches 25.00 mL. Safety First The pH 10 buffer is 10 M ammonia. Keep it under the fume hood as much as possible and avoid breathing its vapors. Wear your goggles! Hint Calculate the mass of disodium dihydrate (CAS 6381- 92-6) needed for the preparation of your stock EDTA solution. The molar mass of EDTA is 372.24 g/mol. EDTA Titrations 28 3. Transfer one 5.00 mL aliquot of the CaCO3 solution to a 125 mL or 250 mL Erlenmeyer flask.