Geology Reference
In-Depth Information
Weight of K in this solution
¼
410 mgcm
3
250 cm
3
¼
102,500 mg
or 102.5 mg
Atomic weight of K
¼
39
:
1
102
:
5
=
39
:
1
¼
2
:
62mmol K in 10 g soil
or 262mmol kg
1
¼
26
:
2 cmol kg
1
As K
1
is monovalent, this is 26.2 cmol of monovalent charge (cmol
c
)
kg
1
and equal to the CEC of the soil.
Concentrations of exchangeable cations in the above soil were: 3480
mg Ca kg
1
; 474 mg Mg kg
1
; 430 mg K kg
1
; and 161 mg Na kg
1
.
What is their concentration in cmol
c
kg
1
, and what is the % base
saturation of the soil?
Atomic weights: Ca, 40; Mg, 24.3; K, 39.1; and Na, 23.
Ca :3480
=
40
¼
87mmol Ca kg
1
¼
8
:
7 cmol Ca kg
1
¼
17
:
4 cmol
c
kg
1
Mg :474
=
24
:
3
¼
19
:
5mmolMg kg
1
¼
1
:
95 cmolMg kg
1
¼
3
:
9 cmol
c
kg
1
K :430
=
39
:
1
¼
11mmol Kkg
1
¼
1
:
1 cmol Kkg
1
¼
1
:
1 cmol
c
kg
1
Na :161
=
23
¼
7mmol Na kg
1
¼
0
:
7 cmol Na kg
1
¼
0
:
7 cmol
c
kg
1
% base saturation
¼½ð
17
:
4
þ
3
:
9
þ
1
:
1
þ
0
:
7
Þ=
26
:
2
100
¼
88%
:
5.5.3 Ligand Exchange (Chemisorption)
Ligand exchange is the process by which ions are held at a solid phase
surface by covalent bonding. The term chemisorption is often used to
describe this process in order to distinguish it from physisorption, where
coulombic bonds are involved and the process is ion exchange (see
previous section).
