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 size
and shape -structural constitution (fig.
5-6)
;
-problems raised by the regular occurrence
of
amorphous compounds in soils
related to
their
formation
and
evolutoin;
-origin
of
their
physicochemical reactivity.
Ortlre
Cristal
idéal
Etat
cristallin
Cristal
réel
FERRIHYDRITE
Kaolinites
Muscovi
te
III
i
tes
Vermiculites
IMOGOLITE
Smecliles
Etat
paracristallin
Halloysi
le
ALLOPHANE
CONSTITUANTS
AMORPHES
Etat
amorphe
Phylol
ilhes
ou
désorganisé
GEL
Si02
Germe
Embryon
50A
O,l/-Lm 1/-Lm
Microcristal
1mm
~~~eO~/t~~
Macrocrista/
=igure 6 Position
of
the secondary
soil
constituents
as
function
of
their
crystallinity
and
particle
size.
Schematic
diagram.
1) Station de Science du Sol -CNRA .
78000
Versailles.
139
Association Française pour l'Etude du Sol - www.afes.fr - 2010
o
o
Intensité
diffractée
20
20
LES
CONSTITUANTS AMORPHES
DU
SOL
1
~I
40
60
80
angle
de
diffraction
C.amorphe
40
60
80
Figure 5 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).
140
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2
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