224
C. De Stefano· C. Foti . A. Gianguzza . D. Piazzese . S. Sammartano
Indeed, only three species [BA, HA and B( OH)] have to be considered. Moreover, only
the self association of BA plays a significant role in marine chemistry studies (at S = 35,
-15% of the sea water salt is associated), since the protonation of anion A and the hydrolysis of cation B are outside the pH range under investigation. Table 9.4 shows equilibrium constants for the self association of the BA salt, 10gKBA' as well as protonation
constants for the anion A Z -, 10gKHA> at different temperatures and salinities. The hydrolysis constant [species B(OH)] can be obtained by the simple equation:
10gK BoH = -12.75 + 0.234[1/2(2 + 3[1/2rl- 0.205[
(9.1)
The thermodynamic parameters in Table 9.4 allow us to complete the definition of
the salt BA, and therefore, to calculate formation parameters for complexes formed
by the minor and trace components of sea water (ligands and lor metal ions) with BZ+
and lor A z-, giving a general picture of the cumulative binding ability of the inorganic
components of sea water.
Table 9.4. Thermodynamic parameters for the self association of BA, for the protonation of A z- and
the hydrolysis of BZ+, at different temperatures and ionic strengths
Reaction
logT K"
DoH (kJ mor')"
~Cp(J K-' mor')"
BZ+ + A Z -= ABO
-0.03
0
0
H+ + AZ-= HA(l-Z)
0.24
14.6
100
Bz+ = B(OH)(Z-l) + H+
-12.75
65.5
-102
T
5
logKsA
logKHA
T
5
logKsA
logKHA
5
5
-0.27
-0.11
5
35
-0.34
-0.24
15
5
-0.27
-0.03
15
35
-0.36
-0.15
25
5
-0.27
0.06
25
35
-0.39
-0.07
35
5
-0.28
0.14
35
35
-0.41
0.02
45
5
-0.28
0.23
45
35
-0.43
0.10
5
15
-0.34
-0.18
5
45
-0.32
-0.25
15
15
-0.35
-0.10
15
45
-0.34
-0.16
25
15
-0.36
-0.01
25
45
-0.37
-0.08
35
15
-0.37
0.07
35
45
-0.40
0.01
45
15
-0.38
0.16
45
45
-0.43
0.09
5
25
-0.35
-0.22
15
25
-0.37
-0.13
25
25
-0.39
-0.05
35
25
-0.40
0.04
45
25
-0.42
0.12
a Att=25"Candl=Omoll-1.