Abstract--Vermiculites and smectites in soils and sediments are frequently partially interlayered or "chloritized". Dioctahedral expansible layer silicates are those most frequently interlayered, and hydroxy-Al appears to be the principal component of the non-exchangeable interlayer material.

A study was made of a Red‐Yellow Podzolic soil with particular regard to the properties of dioctahedral vermiculite, one of its major clay minerals. The soil, Nason silt loam, which is derived from a muscovite schist residuum, was found to be nearly devoid of exchangeable calcium and low in other bases. Although the cation exchange capacity of the B3 horizon was 25 me. per 100 gm. soil, this horizon contained only 0.08 me. Ca per 100 gm. Clay minerals present were kaolinite, dioctahedral vermiculite, and regularly and randomly interstratified illite‐vermiculite. The 14.7A basal spacing of vermiculite from the C1 horizon moved to 10.5A when the clay was K saturated, but the effectiveness of K saturation decreased from the C1 horizon through the A horizon where there was only slight collapse. Boiling the clay from the B1 horizon for 102 hours in 1N KCl caused a change of the 14.7A basal spacing to only 14.2A. However, treatment of the clay in 1N KCl plus 0.1N HCl or treatment with 1N NH4F altered this spacing to near 10A. The difficultly collapsed mineral had a high internal surface, high base exchange capacity, and low divalent cation content. Easily collapsed dioctahedral vermiculite was made difficultly collapsed by repeated Al saturation and drying. Heat treatment at 800°C. collapsed the 14.7A spacing of the mineral in all horizons to 10.3A. Glycerol solvation caused no increase of the 14.7A spacing. These results together with D.T.A. data support the theory that non‐exchangeable Al in the interlayer position in vermiculite restricts collapse of the mineral on K saturation.

No abstract

Previous studies have indicated that Al is fixed by a synthetic cation exchanger as a positively-charged hydroxy-Al polymer with an OH/Al molar ratio of 2. The present study with montmorillonite showed that this mineral also can fix Al in nearly the same OH/AI ratio but at a lower pH.Graded amounts of NaOH were added to an AICl gmontmorillonite suspension and after 6 months the clay was separated. In the solution with the highest (1.35) OH/AI ratio, the apparent CEC of the clay had decreased from 98 to 20.5 me. per 100 g. and a 15.5 A. X-ray diffraction spacing was retained at 500 °C. This sample, however, expanded to 18 A. with ethylene glycol at 25°C. The increase in fixed Al with decrease in CEC was 24.6 mg. per me.Additional evidence is presented which indicates that the CEC was reduced by positively-charged hydroxy-Al groups occupying exchange sites rather than by A1(OH) 3 blocking pathways to these sites.

Abstract-Completeness of exchange of K from muscovite by Ba 2+ ions decreased with particle size below 20/~. Accompanying K exchange at 120~ using a repeated batch technique, was a marked loss of Si and the formation of boehmite in the finer fractions. Several possible explanations for the unexpected high K retention of fine mica fractions are discussed.