1. Standardized sulfuric acid (0.1142 N H2SO4)
  2. Bromcresol green indicator solution - Dissolve 100 mg bromcresol green in 100 mL of about a 1:1 ethanol/deionized H2O solution.
  3. Phenolphthalein indicator solution - Dissolve 0.5 g phenolphthalein in 85 mL 95% ethanol and dilute to 100 mL with deionized water.


  1. Automatic titrator
  2. 150 mL beakers


  1. Pour 100 mL of the sample into a 150 mL beaker.
  2. If free residual chlorine is present, add 1 drop of 1 M Na2S2O3.
  3. Measure and record pH of solution.
  4. Place beaker under electrode, stirrer and titration probe.
  5. If the pH is greater than 8.3 go to step 6.
    1. If the pH is less than or equal to 8.3, go to step 9.
    2. (If the pH is 4.5 or less, the alkalinity equals zero.)
  6. Put 3 drops of the phenolphthalein indicator into the sample. Solution will turn pink.
  7. Titrate to almost clear. (For set-up of control unit see next page.)
  8. Control unit will calculate % phenolphthalein alkalinity. Record on record sheet with one decimal.
  9. Put 5 drops of the bromcresol-green indicator into another 100 mL sample.
    1. (Solution will turn blue.)
  10. Titrate to a clear green (no blue or yellow tints).
  11. Control unit will calculate % total alkalinity. Record on record sheet with one decimal.
  12. When finished cover electrode hole and turn control unit off.


  1. Alkalinity, meq/L = (mL acid)(N H2SO4)(1000)/mL sample
  2. Use the phenolphthalein number in the above equation to calculate the phenolphthalein alkalinity.
  3. Use the bromcresol-green number in the above equation to calculate the total alkalinity.

Control Unit Settings

  1. Sample mg = 1000
  2. pH = 4.5 for total alkalinity
  3. pH = 8.3 for phenolphthalein alkalinity
  4. titrant normality = 0.815

Set-Up of Control Unit

  1. Turn power on. Let unit set-up.
  2. When ENTER DATE APPEARS press next step. Continue pressing next step until modeappears.
  3. Enter 1 for mode. Then continue pressing next step until pH calibr.
  4. Enter Y. Then press next step until Buffer 1 appears.
  5. Uncover electrode hole. Place electrode in yellow pH 7 solution. Press next step.
    1. Wait until Buffer 2 appears.
  6. Rinse electrodes and place in pink pH 4 solution. Press next step.
  7. When calibrated, rinse electrodes and prepare to run samples.
  9. Press Y, then continue pressing next step until SAMPLE 1 MG appears.
  10. Type in 1000 - next step for each sample. When finished press BALANCE PROGRAM.
  11. Place sample 1 under electrode and press START.


  1. Jenkins, S.R., Moore, R. C. January, 1977. A Proposed Modification to the Classical Method of Calculating Alkalinity in Natural Waters. Journal AWWA.P 56.
  2. Larson, T. E., Henley, L. 1955. Determination of Low Alkalinity or Acidity in Water. Anal. Chem. 27:851.
  3. American Society for Testing and Materials. Manual of Water. 1969. 3rd Edition.P 210.