Characteristics of Absorbed Water of Allophane Clay Viewed from the Standpoint of Local Magnetic Field

Nuclear magnetic study on absorbed water of soils (III)

Abstract

Using a broad line N. M. R., the strengths of local magnetic fields were determined which the hydrogen atoms of allophane clay's structural hydroxyle (OH) and its absorbed water receive due to the effects of nuclear spins of such surrounding materials as other hydrogen atoms, aluminum atom nucleus, etc.The followings are the summary of findings from these determinations.
(1) Local magnetic field of dry allophane clay at the room temperature.
The local magnetic field which the hydrogen atom of hydroxyle (OH) of dry allophane clay (treated at 110°C for 24 hours) receives at the room temperature, is small with 1.75 gauss, compared to 5.0 gauss of kaolinite clay and 4.8 gauss of montmorillonite clay under the same condition.
The value of index X which indicates the activity of the hydrogen atom, is very high with 3.3 in case of allophane clay, compared to 1.26 of kaolinite clay and 1.12 of montmorillonite clay.This implies that in allophane clay active hydrogen atom exists under the tested condition.
(2) Relationship between local magnetic field and absorbed water of allohane clay at the room temperature.
As seen in above (1), the dry allophane clay (treated at 110°C for 24 hours) having pF value of 7.30 gives the local magnetic field of 1.75 gauss.It gradually decreases as the pF value drops (absorbed water increases), and finally reaches the bottom point of 0.7 gauss with the pF 4.46 sample where the absorbed water gets saturated.
In allophane clay, there is no stepwise change of the local magnetic field due to the thickness of the molecule layer of absorbed water, as seen in cases of kaolinite clay and montmorillonite clay.
(3) Relationship between local magnetic field and temperature of dry allophane clay.
The local magnetic field which the hydrogen atom of hydroxyle (OH) of dry allopharie clay (treated at 110°C for 24 hours) receives, begins to increase from around minus 5°C foward lower temperatures and reaches 5.0 to 5.2 gauss at around minus 100°C.It remains almost flat down to minus 175°C. This indicates that the activity of the hydrogen atom of the hydroxyle (OH) becomes constant at around minus 100°C.
(4) Relationship between local magnetic field and temperature of allophane clay having 1 to 2 molecule layers of absorbed water.
The local magnetic field which the hydrogen atom of allophane clay having 1 to 2 molecule layers of absorbed water receives, begins to show a sudden increase at minus 55°C foward lower temperatures and becomes constant at around minus 150°C.In case of kaolinite clay having the same molecule layers of absorbed water, it becomes flat at minus 130°C.