Encyclopedia of Environmental Science and Engineering, Volume I and II

0 1 2 3 4 5 678 91011 12 13137

0

–1

–2

–3

–4

–5

–6

–7

0

–1

–2

–3

–4

–5

–6

–7

H+ P 2 P 1

HC–

OH–

C2–

B–

HC–

HB

H 2 C

P 2 P 1

B–

C2–

HC–

HB

H 2 C

seawater

log CONC. (M)

pH

FIGURE 3 Logarithmic concentration—pH equilibrium diagram for seawater as a

closed system. For seawater log BT  3.37, log CT  2.62 and the following pK

values: 6.0 for H 2 CO 3 *, 9.4 for and pK  13.7. BT  total borate boron and CT  total

carbonate carbon. Arrows gives [H] for seawater (pH  8.0) and for two equivalence

points (points of minimum buffer intensity): P 1 , corresponding to a proton reference

level of HB  HC  H 2 O, and P 2 , corresponding to a proton reference level of HB 

H 2 C  H 2 O (From Dyrssen, D. and L.G. Sillén, Tellus, 19, 110, 1967).

TABLE 2B (continued)

Solid acidity constant: HCO 3  H  CO 32 

K 2 3

2

3







{}{ }

{}

HCO

HCO

K′ T

T

2 3

2

3



{}[]

[]

HCO

HCO

cK T

2 3

2

3







[][ ]

[]

HCO

HCO

Temp., °C

Medium

→ 0 Seawater 0.75 M NaCl 1 M KclO 4

— log K 2 log K 2     log K 2    log cK 2

5 10.625a 9.40b ——

5 10.557a 9.34b ——

10 10.490a 9.28b ——

15 10.430a 9.23b ——

20 10.377a 9.17b ——

22 — 9.12c 9.49c —

25 10.329a 9.10b — 9.57d

30 10.290a 9.02b ——

35 10.250a 8.95b ——

40 10.220a —— —

50 10.172a —— —

a H. S. Harned and S. R. Scholes, J. Amer. Chem. Soc. , 63, 1706 (1941).

b After Lyman, quoted in G. Skirrow, Chemical Oceanography, Vol. I, J. P. Riley and G. Skirrow,

Eds., Academic Press, New York, p. 651.

c A. Distèche and S. Distèche, J. Electrochem. Soc. , 114, 330 (1967).

d M. Frydman, G. N. Nilsson, T. Rengemo, and L. G. Sillén, Acta Chem. Scand. , 12, 878 (1958).

Ref.: Stumm, W. and J. Morgan, Aquatic Chemistry, Wiley-Interscience, New York, 1970, pp. 149

and 150.

WATER CHEMISTRY 1261

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