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Re: mass imbalance problem


The mass-balance results look ok to me. I'm guessing that you are not
accounting for the stoichiometric coefficient of uranium in the species. In
the output, the molality applies to the molality of the species. You must
multiply by the stoichiometric coefficient of uranium in the species and
sum the results to obtain the total molality of uranium.

In the following example:

4.2e-4 = 5.078e-005*3 + 3.882e-005*3 + 3.467e-005*4 + 8.014e-006 +
3.630e-006 + 5.466e-007 + ...


David


U(6)            4.200e-004
      (UO2)3(OH)7-     5.078e-005  4.854e-005    -4.294    -4.314    -0.020
      (UO2)3(OH)5+     3.882e-005  3.711e-005    -4.411    -4.431    -0.020
      (UO2)4(OH)7+     3.467e-005  3.314e-005    -4.460    -4.480    -0.020
      UO2(OH)3-        8.014e-006  7.661e-006    -5.096    -5.116    -0.020
      UO2(CO3)2-2      3.630e-006  3.030e-006    -5.440    -5.519    -0.078
      UO2CO3           5.466e-007  5.468e-007    -6.262    -6.262     0.000
      UO2OH+           2.174e-007  2.078e-007    -6.663    -6.682    -0.020
      UO2(CO3)3-4      6.291e-008  3.055e-008    -7.201    -7.515    -0.314
      (UO2)3(OH)4+2    3.270e-009  2.730e-009    -8.485    -8.564    -0.078
      (UO2)2(OH)2+2    3.116e-009  2.601e-009    -8.506    -8.585    -0.078
      UO2+2            6.496e-010  5.423e-010    -9.187    -9.266    -0.078
      UO2SO4           9.341e-011  9.344e-011   -10.030   -10.029     0.000
      UO2(OH)4-2       8.831e-012  7.372e-012   -11.054   -11.132    -0.078
      UO2NO3+          9.089e-013  8.688e-013   -12.041   -12.061    -0.020
      (UO2)3(CO3)6-6   1.413e-013  2.781e-014   -12.850   -13.556    -0.706
      UO2(SO4)2-2      1.334e-013  1.114e-013   -12.875   -12.953    -0.078
      (UO2)2OH+3       5.349e-014  3.563e-014   -13.272   -13.448    -0.176
      UO2Cl+           4.302e-014  4.112e-014   -13.366   -13.386    -0.020
      UO2Cl2           1.132e-019  1.132e-019   -18.946   -18.946     0.000

David Parkhurst (dlpark@xxxxxxxx)
U.S. Geological Survey
Box 25046, MS 413
Denver Federal Center
Denver, CO 80225

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