CHARACTERIZAT ION OF X-RAY AMORPHOUS MATERIAL IN A SCOTT ISH SOIL BY SELECT IVE CHEMICAL TECHNIQUES

They are usually associated with the surface of primary soil particles and consequently when present even in small amounts can have an effect on soil properties incommensurate with the proportion present. Currently, chemical dissolution methods provide the most satisfactory means of assessment. A range of chemical techniques, including dissolution by alkali, dithionite, acid oxalate and pyrophosphate, rimethylsilylation a d fluoride exchange, have been used to examine the inorganic gel in a Scottish brown forest soil developed on glacial till derived from epidiorite. The reactivity of the gel, as determined by fluoride exchange, is similar to that reported for Japanese and New Zealand allophanic soils. It has become increasingly evident that X-ray amorphous inorganic components are of common occurrence in Scottish soils (Mitchell et al., 1964). Many of the early miner-alogical studies of Scottish soils were largely concerned with crystalline inorganic com-ponents since it was generally thought hat poorly-ordered material was mainly restricted to soils in regions of recent volcanic activity (Fieldes, 1955). Although in soils the amount of inorganic gel material is seldom high, it would appear to be frequently associated with the surface of primary soil particles (Follett et al., 1965; Jones & Uehara, 1973; Farme