Table 2.
Stability constants for equilibrium reactions utilized to calculate saturation indices for ZnS(s) (sphalerite), FeS(s) (mackinawite) and FeS2(s) (pyrite).
| 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) From MINEQL+ thermodynamic database [29].
(2) From Hayashi et al. [33] [31].
(3) From Rickard and Luther [35].