Base exchange capacity determination of soils by means of a rapid colorimetric copper method
1941
Sieling, D.H.
A rapid colorimetric method for determining the base exchange capacity of soils based on the sorption of copper from a standard cupric acetate-acetic acid solution by a definite quantity of soil is presented. The exchange capacity is found by measuring the decrease in copper concentration produced in a measured volume of the cupric acetate-acetic acid reagent by a weighed quantity of soil. The acidity of the reagent is adjusted to 0.07 normal with respect to acetic acid and to 0.2 normal in cupric ions for best results. The soil is shaken with the reagent to insure a practically complete reaction and the resulting suspension is filtered. The quantity of copper remaining in a measured volume of the filtrate is determined colorimetrically by treating the filtrate with dilute ammonium hydroxide to produce the stable, highly colored cupra-ammonio complex ion and then comparing the intensity of the color produced with standards containing known quantities of copper. The values obtained by this quick method with 21 soils correlated reasonably well with those obtained by two different leaching methods and took only a fraction of the time required by the leaching methods. Visual comparison of the unknown solutions with the standards was made in a simple and convenient combination filter rack and color comparator.
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