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Table 2 Stability constants for equilibrium reactions utilized to calculate saturation indices for ZnS(s) (sphalerite), FeS(s) (mackinawite) and FeS2(s) (pyrite).

From: Formation of Zn- and Fe-sulfides near hydrothermal vents at the Eastern Lau Spreading Center: implications for sulfide bioavailability to chemoautotrophs

 

log K (I = 0)

 

25°C(1)

100°C(2)

150°C(2)

240°C(2)

H2O(l) ⇔ H+ + OH-

-14.0

-12.22

-11.59

-11.08

H2S(aq) ⇔ HS- + H+

-7.0

-6.38

-7.62

-7.57

HS- ⇔ S2- + H+

-17.0

-16.01

-15.51

-14.83

Zn2+ + Cl- ⇔ ZnCl+

0.4

1.22

2.05

4.13

Zn2+ + 2Cl- ⇔ ZnCl20

0.6

1.87

3.08

5.29

Zn2+ + 3Cl- ⇔ ZnCl3-

0.5

2.32

3.74

6.42

Zn2+ + 4Cl- ⇔ ZnCl42-

0.19

1.45

2.61

5.8

Zn2+ + 2HS- ⇔ Zn(HS)20

12.82

11.94

12.05

13.26

Zn2+ + 3HS- ⇔ Zn(HS)3-

16.1

13.21

13.4

15.43

Zn2+ + 2HS- ⇔ ZnS(HS)- + H+

6.81

6.14

5.89

5.99

Zn2+ + 3HS- ⇔ ZnS(HS)22- + H+

6.12

5.56

5.22

N/A

Zn2+ + 2HS- + Cl- ⇔ Zn(HS)2Cl-

N/A

13.16

13.42

14.33

Zn2+ + HS- ⇔ ZnS(s) + H+

11.45

10.59

10.4

10.79

Fe2+ + 2HS- ⇔ Fe(HS)20

8.95

   

Fe2+ + 3HS- ⇔ Zn(HS)3-

10.99

   

Fe2+ + HS- ⇔ FeS(s), mackinawite + H+

3.6

   

Fe2+ + HS- + S0(s) ⇔ FeS2(s), pyrite + H+

14.2(3)

   
  1. (1) From MINEQL+ thermodynamic database [29].
  2. (2) From Hayashi et al. [33] [31].
  3. (3) From Rickard and Luther [35].