Free Energy in Cation Interchange as Illustrated by Plant Root

Free Energy in Cation Interchange as Illustrated by Plant Root–Substrate Relationships. C. E. Marshall, and Wm. J. Upchurch. J. Phys. Chem. , 1953, ...
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C. E. MARSHALL AND WM.J. UPCHURCH

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Vol. 57

FREE ENERGY I N CATION INTERCHANGE AS ILLUSTRATED BY PLANT ROOT-SUBSTRATE RELATIONSHIPS' BY C. E. MARSHALL AND WM. J. UPCHURCH Department of Soils, University of Missouri, Columbia, Mo. Received March 2 , l g 6 3

Three methods for the determination of free energy changes in ionic-exchange reactions between two colloidal systems are formulated, ( I ) potentiometric through activity determinations, (11) by small exchange taking two cations a t a time, (111) by equilibration, separation and analysis. The characteristics of a cation-exchanger Amberlite IR-120 with respect to potassium calcium and hydrogen ions are given. It is shown to be markedly multifunctional, the bonding energy for potassium showing a range from