Accurate approach for determining fresh-water carbonate (H 2CO3*) alkalinity, using a single H 3PO4 titration point

Liat Birnhack, Sara Sabach, Ori Lahav*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

6 Scopus citations


A new, simple and accurate method is introduced for determining H 2CO3* alkalinity in fresh waters dominated by the carbonate weak-acid system. The method relies on a single H3PO4 dosage and two pH readings (acidic pH value target: pH∼4.0). The computation algorithm is based on the concept that the overall alkalinity mass of a solution does not change upon the addition of a non-proton-accepting species. The accuracy of the new method was assessed batch-wise with both synthetic and actual tap waters and the results were compared to those obtained from two widely used alkalinity analysis methods (titration to pH∼4.5 and the Gran titration method). The experimental results, which were deliberately obtained with simple laboratory equipment (glass buret, general-purpose pH electrode, magnetic stirrer) proved the method to be as accurate as the conventional methods at a wide range of alkalinity values (20-400 mg L-1 as CaCO3). Analysis of the relative error attained in the proposed method as a function of the target (acidic) pH showed that at the range 4.0<pH<4.5 the error was minimal. A suggested experimental setup for continuous alkalinity measurement is also described.

Original languageEnglish
Pages (from-to)12-20
Number of pages9
StatePublished - 15 Oct 2012
Externally publishedYes


  • Alkalinity analysis
  • Carbonate alkalinity
  • Fresh water
  • Single titration


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