A simple method for measuring the carbonate content of soils

The traditional measurement of the carbonate content of soils with the Scheibler apparatus is slow and labor intensive. Our objective was to develop a relatively simple and accurate method. The pressure calcimeter principle was used; the pressure change caused by the reaction between HCl and a weighed soil sample was measured with a digital plunge-in manometer through a silicone-rubber septum placed on a screw-capped tube. The method was calibrated with pure CaCO3. The correlation between the measured and weighed amounts was excellent (r(2) = 0.999). The carbonate content of a natural soil sample was measured 10 times; the coefficient of variation was 1.9%. Ten ISE (International Soil-Analytical Exchange) samples were analyzed with this method which contained a carbonate content of 3 to 170 g kg(-1). Satisfactory results were obtained, indicating the suitability of the proposed method for practical purposes.