The Use of Thermometric Titrations in Soil Chemistry Studies
1962
Ragland, John L.
It was determined that a thermometric titration procedure could be used to obtain the cation-exchange capacities and heats of neutralization of acid-saturated clays. The endpoints of these titration curves were much sharper than those commonly obtained by potentiometric or conductometric methods. Cation-exchange capacities calculated from thermometric titration curves of H-exchanges agreed fairly well with those determined by the BaCl₂-TEA method. Heats of neutralization for Arizona, Mississippi, Southern and Utah bentonites were found to be: −13.3 ±2, −15.9 ±3, −16.1 ±1 and −15.5 ±2 kcal. per eq., respectively. The heat of neutralization of humic acid was −13.2 ±1 kcal. per eq. and that of Al-saturated Mississippi bentonite was −5.5 kcal. per eq. The large difference in the heat of neutralization of the H- and Al-saturated exchangers causes titration curves for the two to have widely differing slopes. This allows determination of the proportions of H and Al saturations of mixed H-Al clays from the titration curves. The possible use of thermometric titrations in determining the course, mechanism and rate of a number of chemical reactions in soils is discussed and concluded to be excellent.
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