The determination of carbonates in soils and aggregates through the measurement of the “loss on ignition” by calcination at 1000°C does not make it possible to discriminate between calcium carbonate, magnesium carbonate, and the double carbonate of calcium and magnesium (“dolomite”).
The measured value may also include the crystallization water and constitutional water of certain compounds as well as any organic matter contained in the samples.
The operation procedure described in the paper is based on the hot acid attack of a test portion of the sample to disengage the carbon dioxide, which is caught in a titrated mixed solution of barium hydroxide and potassium hydroxide. In the acid attack solution, the calcium and magnesium ions are determined by complexometry (possibly by atomic emission or absorption).
The advantage of the method lies in the interpretation of the results. A comparison of these with the theoretical contents calculated for calcium carbonate, magnesium carbonate, and the double carbonate of calcium and magnesium generally makes it possible to discriminate between the various probable carbonates of the analyzed sample. In some cases, the presence of other calcium and magnesium salts can be demonstrated. A number of concrete and experienced examples are presented.