1974 Volume 43 Issue 2 Pages 129-137
The relationship between the mineralogical composition and colloid-chemical properties of clay particles of reclaimed lands for mulberry field was studied on Nakamura soil, Osaka soil, Miyake soil, Akasaka soil, and Yokawa soil of Hyogo prefecture. The mineralogical composition was studied by the X-ray diffraction method and the zeta-potential was measured by the ultramicro-electrophoresis. The results obtained were as follows:
1) The clay mineral of Nakamura soil and Osaka soil were rich in the illite, while Miyake soil consisted mostly of chlorite (trioctahedral) with very small amounts of Al-inter layer mineral, primarily quartz. However, Yokawa soil clay showed clearly the variable expansion depending on the saturating cation K or Ca and glycerol, the soil clay are composed mostly of montmorillonite. These soil clay minerals were dominated by a single mineral respectively and were dependent upon the parent rock material.
2) These clay particles have the negative charge over the pH range from about pH 3 to 10. The negative zeta-potential decreased markedly with the decrease in pH in the case of the mulberry field soils tested. However, in the case of Yokawa soil clay (uncultivated soil rich in montmorillonite clay), the zeta-potential was almost independent on pH over the pH range from about 3 to 6. The zeta-potential at high pH increased markedly with the increase of additional negative charge on all clay particles.
3) The negative zeta-potential of clay particles decreased with the increase in the electrolyte concentration (thorium nitrate, lanthanum nitrate and calcium nitrate), but point of zero charge, i, e, the electrolyte concentration at which the particle charge become zero differed markedly from clay to clay (Akasaka soil<Miyake soil<Osaka soil<Nakamura soil<Yokawa soil). This sequence could be explained by the clay mineral compositions of the soils.
