Routine Procedure for Rapid Determination of Soil Carbonates

A procedure is presented for the routine determination of soil carbonates based on the following reaction: CaCO₃ + 2 HC₂H₃O₂ → Ca²⁺ + 2 C₂H₃O₂^‐ + H₂O + CO₂ (g) A known quantity of acetic acid is added to a known quantity of soil. The pH of the reaction mixture is then determined following complete dissolution of CaCO₃. Calcium carbonate content is determined empirically from a standard curve relating pH to known CaCO₃ content according to the equation: pH = K + n log [CaCO₃/(T − CaCO₃)], in which T equals the total amount of calcium carbonate which could be completely dissolved by the acetic acid added to the system, and K and n are constants. Several possible sources of error exist in the procedure; however, potential errors may be minimized by the maintenance of optimum working conditions. Results obtained by the acetic acid procedure compared favorably with results obtained by the Chittick procedure. The proposed procedure has the advantage of simplicity and offers a rapid alternative for routine determination of soil carbonates.