The Acidity to Carbonate Component Correction

Titrating an acid solution to a p of 8.3 converts all the H2CC 3 species to HCOjT by reaction (3.72). In 3.9.4 we saw that for solutions having a / H less than 8.5 (which would include most natural solutions), the alkalinity titration is essentially a measure of mHCO-. Therefore for most natural solutions, in which other reactions such as (3.58)-(3.63) or (3.74M3.77) are not significant, the sum of the alkalinity and acidity titrations is a measure of the total carbonate content.8 

If the acidity titration is carried out to pH 11, it is twice the total carbonate. 

Correcting the titration acidity for the presence of competing acids in order to obtain a better estimate of mH2CO presents the same problems as discussed previously ( 3.9.3), and the same remedy is proposed, i.e., the solution analysis should be titrated using a program such as phreeqc, as discussed in Chapter 8. 

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