UCL Department of Geography


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UCL Home  /  Geography  /  Resources  /  Laboratory  /  Laboratory Methods  /  Lake Sediment Analysis  /  Percentage Carbonate Content

Percentage Carbonate Content

The carbonate content of the sediment can be roughly determined by heating the sediment to 950°C. The amount of carbon dioxide lost in the process, as carbonates are converted to oxides, can be used to determine the original carbonate content of the sediment.


Clean, dry porcelain crucibles, spatula, balance weighing to 4 decimal places, furnace set to 950°C, desiccator.


The weighed ash samples (see method for loss on ignition) are placed in the furnace and heated to 950°C for 4 hours. The furnace door is then opened to allow the heat to disperse (or left closed to cool overnight) and the crucibles removed and placed in a desiccator as described above. When cool the samples are re-weighed and the difference between the ash weight and the weight lost at 950°C is multiplied by 1.36 (the difference between the molecular weights of CO2 and CO3) to derive the carbonate content which can then be expressed as a percentage of the dry weight.

Calculation of the above can be carried out using COREDAT.