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Calcium Carbonate Equivalency (CCE)

Standards:

  1. Potassium Biphthalate Solution (0.6476N): Prepare by dissolving 33.0648 g of pure, dry KHP in about 450 mL of deionized water in a 500 mL volumetric flask. Dilute to volume and mix well.
  2. Standard NaOH solution (0.6476N): Prepare 2.5 L quantity by diluting 113 mL of 40% NaOH w/w into 2387 mL deionized H2O. Standardize by titrating against KHP solution prepared above. Pipet 50 mL of KHP solution into a 150 mL beaker, add a few drops of phenolphthalein indicator and titrate the NaOH into the KHP solution to a permanent light pink endpoint. If exactly 25.00 mL of NaOH is not titrated, adjust NaOH solution and repeat. Protect from exposure to air by a soda-lime tube or other suitable means.
  3. Standard HCl solution (0.9714N): Dilute 200 mL conc. HCl into 2300 mL of deionized water. Standardize against 0.6476N NaOH by dispensing 25 mL of HCl from a buret into a 150 mL beaker. Add a few drops of phenolphthalein indicator and titrate HCl against NaOH to a permanent light pink endpoint. If exactly 37.50 mL of NaOH are not titrated, adjust HCl solution and repeat.

Reagents:

  1. Phenolphthalein indicator: Dissolve 1.0 g phenolphthalein powder in 70 mL of ethanol, add 30 mL of deionized water and mix well.

Sample Preparation:

  1. Weigh exactly 1.0 g of sample and transfer quantitatively into a 250 mL conical beaker.
  2. Add 25.00 mL of 0.9714N HCl, add about 50 mL of deionized water, cover with a watch glass and bring to boiling on a hot plate for 5 minutes. Remove from heat, cool and rinse condensate from watch glass back into beaker. Also, rinse walls of beaker with minimal amount of deionized water.

Procedure:

  1. 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.

Calculations:

  1. CaCO3 Equivalent = (75 - 2(mL NaOH titrated)) x 1.629

Reference:

  1. Adapted from Method 955.01, 16th edition of the Official Methods of Analysis, Association of Official Agricultural Chemists.