Application of thermogravimetry to the analysis of carbonates occurring in soils. II.—Analysis of carbonates in soils

The values for total carbonates in soils as measured by thermogravimetry were in good agreement with those obtained by chemical determinations. While the pyrolysis curves of some soils allowed a partitioning of the total carbonate, difficulties were encountered in this regard with others. For most of the soils where partitioning was possible, the results for dolomite were higher, and those for calcite lower, than values obtained by a chemical method. In order to determine the possible causes for this anomalous behaviour the interaction during pyrolysis between various inorganic salts and quartz with calcite was studied. Evidence is presented to show that the difficulty can be traced to an interaction between sodium and/or potassium and silica with calcite. Accordingly, caution should be exercised in interpreting thermogravimetric curves of soils for the purpose of partitioning the total carbonate content into dolomite and calcite.