> I`d like to introduce MnS-Species to the database, but cannot find log_k values and delta_h values for the complex MnS(HS)- and the preciptitation of MnS2. Well, I do find a log_K for MnS(HS)- of +37.25 in Landing, W.M. and Lewis, B.L., 1991. Thermodynamic modelling of trace metal speciation in the Black Sea. In: E. Izdar and J.W. Murray (Editors), Black Sea Oceanography. NATO ASI Series C. Kluwer Academic Publishers, Dordrecht, pp. 125-160. > But this value seems rather high to me. Putting this in the database, all the solute Mn is in this MnS(HS)- species, and all others are negligible, which seems not to be right to me. I've had that problem with sulfide and polysulfide species too. The literature values appear to apply to specific systems and are not generally usable. The polysulfides can cause some strange physical results (inability to reach mineral saturation because the complexes are so strong) or cause the numerical method to fail. As you probably know, none of the databases distributed with phreeqc have Mn-sulfide complexes. I think only wateq4f.dat even has iron bisulfide complexes. None have a phase MnS2. > Do you have any idea how to find the log_k and delta_h values? I would be greatful for any hint. I'm afraid I don't know of any thermodynamic data. Other than searching the literature for more, the only suggestion I could make is to use iron as an analog and include Mn-bisulfide complexes with the same K's as Fe-bisulfide. I don't know if there really is an MnS2 phase, but you could copy pyrite or marcasite for Mn. David David Parkhurst (dlpark@xxxxxxxx) U.S. Geological Survey Box 25046, MS 413 Denver Federal Center Denver, CO 80225 Project web page: https://wwwbrr.cr.usgs.gov/projects/GWC_coupled
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