Relibility of methylene blue excgange methods for estimation of cation-exchange capacity of different Egyptian soils and pure clay minerals M. H. A. Ghali, M. E. Abdel-Rahman.

الملخص EN

This study was carried out to certify methylene blue (MB) exchange method as a rapid one for determination of cation-exchange capacity CEC of different Egyptian soil locations having a wide range of variation in soil physical and chemical properties as soil texture, structure, CaCO3, pH, O.M, and CEC as well as three pure clay minerals, namely: Namontmorillonite و(Wyoming, U.S.A) ; Palygorskite (Georgia U.S.A) and Kaolinite (Scalby, England).

Four methods were tested to estimate CEC of such soils and these 3 pure clay minerals.

These methods were conventional Na-NH4 exchange ; MB-acid, MB-tetra sodium pyrophosphate (TSPP) and MB water filter paper spot test titration methods.

Soil samples were analyzed under suitable conditions of concentration, equilibration period and flocculation of MB solutions.

The squared regression coefficient (R2) of MB-TSPP vs.

Na-NH4 exchange methods for soil samples was 0.98.

The R2 of MB-water vs.

Na-NH4 exchange methods for pure clay mineral samples was 1.0.

The MB test is a simple, rapid and economical method to determine CEC.

The CEC values measured by MB-TSPP were closed to the calculated values for different Egyptian soils.

But the values determined by MB-water were closed to the calculated values for pure clay minerals.

The MB-TSPP and MB-water exchange methods may be suitable for the field-testing of soils and pure clay minerals, respectively.