C. E. MARSHALL AND WM.J. UPCHURCH
618
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