SOLUTION SPECIES problem

[EMH121]

When I modified the LLNL DB by adding the following, and running for 25oC

SOLUTION_SPREAD
    -pH       6.0
  Number       pe     S
      1        2    28
      2        1    28
      3        0    28
      4       -1    28
      5       -2    28
      6       -3    28
      7    -3.66    28
      8       -4    28
      9       -5    28
     10       -6    28
     11       -8    28
     
   
 SOLUTION_SPECIES

SO4-2 + H+ = HS- + 2O2
   -log_k   -132.56

output was reasonable and different from an identical LLNL DB (log_k = -138.32) run that did not have the SOLUTION_SPECIES keyword block.

When I added the T-informing "analytical" line as well, as below, the output warned "max iterations exceeded 100" and the output did not include any real sulfate data. The analytical expression constants are of the prescribed form a + b*x + c/x +d*log10(x) + e/(x^2) + f*(x^2)

SO4-2 + H+ = HS- + 2O2
   -log_k   -132.56
   -analytical   1.71E+04   4.83E+00   -7.86E+05   -1.24E+03   3.53E+07   -1.49E-03

The analytical expression returns log_K = -132.54 when calculated in Excel. Can someone help please? Thanks in advance for your help!

[dlparkhurst]

The following produces the output:

HS- Log K:    1.3100e+04

So, I think your analytical expression is not correct.

SOLUTION_SPECIES
SO4-2 + H+ = HS- + 2O2
   -log_k   -132.56
   -analytical   1.71E+04   4.83E+00   -7.86E+05   -1.24E+03   3.53E+07   -1.49E-03
USER_PRINT
-start
10 PRINT "HS- Log K: ", LK_SPECIES("HS-")
-end
SOLUTION
END

[EMH121]

Thank you Dr Parkhurst! My error was in the d*log10(T) term. The correct d constant in this case is -6583.929939. The keyword block below worked without error.

 SOLUTION_SPECIES

SO4-2 + H+ = HS- + 2O2
   -log_k   -132.56
   -analytical   1.71E+04   4.83E+00   -7.86E+05   -6583.929939   3.53E+07   -1.49E-03

[MichaelZ20]

Calculated log_k equals -123.04