The solubility of potassium from soil illites. V. Interlayer hydrogen ions; heats of reaction; and synopsis

Abstract

When potassium is readsorbed at interlayer sites in soil illites after displacement in calcium chloride solution, hydrogen ions are released in proportions ranging from 1/6 to 1/10 of the potassium adsorbed. This supports the conclusions of earlier work that release of potassium by calcium ions from these sites requires the intervention of hydrogen ions in the approximate ratio of one hydrogen ion to three calcium ions. The release of potassium increased about 1.4 times for a temperature rise from 10 to 30°C. The heat of reaction was 3 or 4 kcal/mole potassium released. This is consistent with a reaction between ions and charged sites as the heats of many ionic reactions are of this magnitude; and it appears to be less than the heats of decomposition of the clay mineral lattice. A summary of the findings of Parts I-V of this series appears in the Synopsis