Gypsum solubility in sulfuric acid

[IliasBouchkira]

Dear all

Can anyone tells me how to plot the solubility of gypsum in sulfuric acid like in the figure (exemple),

Thank you very much in advance,

[dlparkhurst]

The following script makes a similar graph. The pitzer.dat database is most appropriate for the calculation.

If you want to overlay additional experimental data, see the -plot_tsv_file option of USER_GRAPH.

Code: [Select]

SOLUTION 1
temp 42
END
EQUILIBRIUM_PHASES 1
Gypsum 0 10
END
USE solution 1
USE equilibrium_phases 1
INCREMENTAL_REACTIONS
REACTION 1
H2SO4 1
4 mole in 40 steps
USER_GRAPH 1
    -headings               Pitzer.dat
    -axis_titles            "H2SO4 concentration, moles per kilogram water" "Gypsum solubility, moles per kilogram water" ""
    -chart_title            "Gypsum Solubility at 42 C"
    -initial_solutions      false
    -connect_simulations    true
    -plot_concentration_vs  x
  -start
10 acid = GET(1) + RXN
20 PUT(acid, 1)
30 PLOT_XY acid, TOT("Ca"), SYMBOL = None,            COLOR = Black, LINE_WIDTH = 1
  -end
    -active                 true
END


[IliasBouchkira]

Thank you very much dear professor,

I wonder also if there is a database to compute the solubility of the hemihydrate (CaSO4:0.5H2O) ? i looked for the bassanite in all the databases and i can't find it.

i wanted also to add it as shown below but i don't have the needed data:


Hemihydrate
   CaSO4:0.5H2O = Ca+2 + SO4-2 + 0.5 H2O
   -log_k   ...
       -delta_h ...
   -analytical_expression  ...
   -Vm ...

[dlparkhurst]

There are definitions of Bassanite in ColdChem.dat, core10.dat, llnl.dat, and sit.dat.

I might use ColdChem.dat or at least the analytical expression from ColdChem.dat; you can use the notes in the database to find the original reference.