ABSTRACT
Many reactions of soils occur at the surfaces of their particles, and, as a result, there are close relationships between measures of surface area and certain soil properties. In particular cation exchange capacities (CECs) have been found to correlate strongly with specific surface areas – or surface area per gram – particularly when these are measured by the retention of polar molecules, such as ethylene glycol and ethylene glycol monoethyl ether. Generally, the charge on soils is measured as CEC because most soil clays are net negatively charged, as is organic matter. Soil chemistry is largely surface chemistry and large surface areas are largely a consequence of fine particle sizes. The smaller the particles, the more extensive and hence adsorptive are their surfaces. Particle size distributions and determinations inevitably follow disaggregation and/or dispersion procedures that are unrealistic for natural soil associations.
