Which extract is used for determination of CEC

1N NH₄ OAC (ammonium acetate) is the extract used for the determination of CEC, Cation exchange capacity.
In this method, the soil is leached with an excess of neutral, in 1 N ammonium acetate solution to remove the exchangeable cations and to saturate the exchange material with ammonium. Sodium is a saturated cation and is moved by an ammonium cation. The CEC is calculated based on the concentration of sodium ions in the extract.