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This chapter discusses the procedures for the determination of quantity, reactivity and equilibrium relations of the carbonate minerals and gypsum. Inorganic carbonate in soil occurs predominantly as the sparingly soluble alkaline-earth carbonates, calcite and dolomite. Calcite is usually the dominant form in active pedogenic environments. A modification of the pressure-calcimeter procedure based on the relative rates of reaction of calcite and dolomite has been used to quantitatively determine calcite and dolomite in mixed-phase systems. In the volumetric calcimeter method, the carbonates are treated with excess acid and the CO2 is determined volumetrically. Acetic acid dissolution procedure provides a means of obtaining quantitative determinations of soil carbonate with readily available equipment, but it is subject to errors to which the CO2 evolution procedures are not subject. The pH-stat procedure for carbonate reactivity provides an excellent means of comparing soils with respect to relative carbonate reactivity.