338
Chemical Oceanography, 4th Edition
ln K 2 = 172.1033 – 8814.71/T – 27.927 ln T + (1.3566 – 160.340/T) S 0.5
+ (–0.05778 + 0.37335/T) S
(8.18)
ln K 3 = –18.126 – 3070.75/T + (2.81197 + 17.27039/T) S 0.5
+ (–0.09984 – 44.99486/T) S
(8.19)
The calculated percentage of the various forms of phosphate in H 2 O, NaCl, and seawater
as a function of pH are shown in Figure 8.1. At pH 8.1, the percentage of each species is
given in Table 8.4.
Water
pH
6.0
6.5
7.0
7.5
8.0
8.5
9.0
pH
6.0
6.5
7.0
7.5
8.0
8.5
9.0
Fraction
0.0
0.2
0.4
0.6
0.8
1.0
HPO 4
2–
HPO 4
2–
HPO 4
2–
PO 4
3–
H 2 PO 4
–
H 2 PO 4
–
H 2 PO 4
–
Fraction
0.0
0.2
0.4
0.6
0.8
1.0
NaCl (0.7 M)
Seawater (S = 35)
pH
6.0
6.5
7.0
7.5
8.0
8.5
9.0
Fraction
0.0
0.2
0.4
0.6
0.8
1.0
Figure 8.1
The various forms of phosphoric acid in water, NaCl (0.7 M), and seawater (S = 35).