Use of an automatic CHN analyzer to determine organic and inorganic carbon in soils

Differential thermal analysis shows that in soils organic matter and carbonates react in very different temperature ranges. An automatic CHN Analyzer was therefore used to determine the organic and inorganic carbon content of soils. At 500°C complete oxidation of soil organic matter occurs without appreciable decomposition of carbonates. Because only elemental carbon is determined, interferences due to weight losses from structural water in clays are eliminated. Decomposition of carbonates begins above 500° and always is concluded before 1100°C. Total organic and inorganic carbon in soils thus may be determined by running replicates at 500° and 1100°C with the Analyzer.