AMORPHOUS SOll CONSTITUENTS • AN INTRODUCTION

SCIENCE DU SOL n° 1986/1 - pp. 139-140 - PLAISIR-FRANCE
AMORPHOUS SOll CONSTITUENTS • AN INTRODUCTION
G. PEDRO
(1)
(Science du Sol 1983/3-4)
This introduction is focused chiefly on the following three basic points :
-
general characteristics of amorphous soil constituents - chemical composition
and shape - structural constitution (fig. 5-6) ;
-
problems raised by the regular occurrence
related to their formation and evolutoin;
-
origin of their physicochemical reactivity.
of
amorphous
compounds
size
in soils
Ortlre
Cristal
idéal
Etat cristallin
Cristal réel
FERRIHYDRITE
Kaolinites
Muscovi te
III i tes
Vermiculites
Smecliles
IMOGOLITE
Halloysi le
Etat paracristallin
ALLOPHANE
CONSTITUANTS
AMORPHES
Etat amorphe
ou désorganisé
Phylol ilhes
GEL Si02
50A
O,l/-Lm
=igure 6
1) Station
1/-Lm
Microcristal
Germe
Embryon
1mm
~~~eO~/t~~
Macrocrista/
Position of the secondary soil constituents as function of their crystallinity
and particle size. Schematic diagram.
de
Science
du
Sol
- CNRA
. 78000
Versailles.
Association Française pour l'Etude du Sol - www.afes.fr - 2010
139
LES CONSTITUANTS AMORPHES DU SOL
Intensité
diffractée
1
o
20
40
60
~I
80
angle de diffraction
C.amorphe
o
Figure 5
140
20
40
60
80
Comparison between diffraction diagrams of crystallized compounds into
small crystals and amorphous solids. From top to bottoms : crystal size 1{.L,
then 50 A, finally the solid in amporhous state (A. Guinier, 1980 ,p. 212).
Association Française pour l'Etude du Sol - www.afes.fr - 2010