UNE-EN ISO 23470:2018

This International Standard specifies a method for the determination of cation exchange capacity (CEC) and the content of exchangeable cations (Al, Ca, Fe, K, Mg, Mn, Na) in soils using a hexamminecobalt trichloride solution as extractant. For soils containing calcium carbonate a calcite saturated hexamminecobalt trichloride solution is specified particularly for determination of exchangeable Ca. This method was introduced to avoid erroneous (inflated) Ca values. This International Standard is applicable to all types of air-dry soil samples which have been prepared in accordance with ISO 11464.

Hexamminecobalt trichloride is recommended as an extractant for non-calcareous soils with a pH value < 6.5. As the pH value of a soil suspension in the hexamminecobalt trichloride solution is close to the pH value of the suspension in water, this method is considered to give the effective CEC, i.e. the CEC at the soil pH value(e.g. according to ISO 11206).

A calcite saturated hexamminecobalt trichloride solution is recommended for calcareous soils with a pH value > 6,5. Here only the exchangeable cations Ca, Mg, K and Na plus the total CEC are determined. The pH value of the calcite saturated hexamminecobalt trichloride solution is approximately 9. Thus the results are comparable to the determination of potential CEC (e.g. according to ISO 13536).

Reference and results of the comparison with other methods (barium chloride, ammonium acetate) are given in Annex A.