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number of documents in this section: 1 section: | Mineral Soils conditioned by a wet (sub) Tropical Climate | Acrisols | Excursus: Cation exchange capacity (CEC)vorherigeprevious | nextvorherige   
Ferralsols
Alisols
Nitisols
Acrisols
Excursus: Cation exchange capacity (CEC)
Excursus: Clay eluviation
Excursus: Process of ferralitization
Excursus: Aluminium toxicity
Lixisols
glossarysearch :

Cation exchange capacity (CEC)

CEC:

  • Is defined as the sum total of the exchangeable cations that a soil can absorb at a specific pH.

Expression:

  • Is expressed as the number of moles of positive charge adsorbed per unit mass.
  • Mostly: centimoles of charge per kilogram of soil (cmolc/kg).

Example:

  • CEC of 15 cmolc/kg: 1 kg soil can hold 15 cmolc of H+ ions and can exchange this number of charges from H+ ions for the same number of charges from any other cation [emphasis: exchange reactions take place on a charge-for-charge basis and not an ion-for ion-basis].
Chemical expression
  • The CEC commonly varies from 0.03 and 0.5 mole of positive charge (molc) per kilogram of soil.
  • To express the CEC in whole numbers, the charge is usually indicated in centimoles per kilogram (cmolc/kg): (100 cmol make up 1 mole. The range of CEC of soils is 3 to 50 cmolc/kg)