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ThommyW

Thermo data coefficients CO2 H2O ... URGENT !!!!

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Hello Tom,

What are the values tabulated in the thermo file,

and given below ? For which species exactly and which

reaction or/equation these values below are valid ????????

* c co2 1

0.1224 0.1127 0.0934 0.0802

0.0843 0.0989 0.1371 0.1967

* c co2 2

-0.0047 -0.0105 -0.0036 -0.0015

-0.0118 -0.0104 -0.0071 -0.0181

* c co2 3

-0.0004 0.0015 0.0001 0.0005

0.0031 0.0014 -0.0029 -0.0025

* c co2 4

0.0000 0.0000 0.0000 0.0000

0.0000 0.0000 0.0000 0.0000

* c h2o 1

0.500000E+03 0.145397E+01 0.500000E+03 0.155510E+01

0.162250E+01 0.500000E+03 0.500000E+03 0.500000E+03

* c h2o 2

0.500000E+03 0.223570E-01 0.500000E+03 0.364780E-01

0.458910E-01 0.500000E+03 0.500000E+03 0.500000E+03

* c h2o 3

0.500000E+03 0.938040E-02 0.500000E+03 0.643660E-02

0.452210E-02 0.500000E+03 0.500000E+03 0.500000E+03

* c h2o 4

0.500000E+03 -0.536200E-03 0.500000E+03 -0.713200E-03

-0.831200E-03 0.500000E+03 0.500000E+03 0.500000E+03

In looked in the archive but I found only one item of 2004 what was not sufficiently exact.

I also looked in the reference but only a general description is given. (see below )

-------------------------------------------------------------------------------------

......

Following the temperature table are tables giving pressure, coefficients for calculating

parameters in activity coefficient correlations, and so on, at each of the principal temperatures.

The tables look like:

Thermo Datasets

..................

...

----Coefficients for calculating the activity coefficients for CO2 and some other electrically neutral species,---

WHICH SPECIES /REACTION /equations / type of VALUES FOR ALL OF THE 4 GRIDS ????????????????????

Coefficients for calculating the activity of water,

WHICH SPECIES/ REACTION /equations / type of VALUES FOR ALL OF THE 4 GRIDS ????????????????????

--------------------------------------------------------------------------------------------------------------------------------

I need to know all this exactly because I need perhaps to recalculate these values by our own thermodynamic data, depends....

Thanks very much

ThommyW

PS: What about log(K) for H2O(liq) --> H2O(g)

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Hi Thomas:

The equations used to calculate the activities of electrically neutral species and water are given in chapter 8 of Geochemical and Biogeochemical Reaction Modeling (or chapter 7 if you have the older Geochemical Reaction Modeling).

Be sure you also understand the importance of the ion size parameter which is described in the Thermo Datasets Appendix of the GWB Reference manual as follows:

neutral_species.gif

Hope that helps,

Tom Meuzelaar

RockWare, Inc.

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Hi Thomas:

The equations used to calculate the activities of electrically neutral species and water are given in chapter 8 of Geochemical and Biogeochemical Reaction Modeling (or chapter 7 if you have the older Geochemical Reaction Modeling).

Be sure you also understand the importance of the ion size parameter which is described in the Thermo Datasets Appendix of the GWB Reference manual as follows:

neutral_species.gif

Hope that helps,

Tom Meuzelaar

RockWare, Inc.

Hello Tom,

For CO2 the given data correspond to the equation for neutral species log gamma = a* I + b * I^2 + c* I^3

and the given data to those given in the book, discussing this equation for the b-dot model.

But it is not clear to me why there is a fourth grid with only zero's.

This does not make sense if these parameters refer to an equation with 3 parameters.

Furthermore, if I understood you right, the H2O data refere to the B-Dot equation (8.6) with 4 parameters:

phi = 1 - 2,303 A/(a^3 * I) (b - 2 ln(b ) - 1/b ) + B* I/2 + 2 C* I^2/3 + 3D* I^3/4

because 4 data sets are given. What is striking is, that all data given in the book are higher

by a factor of 10. What value is used ? Why is there a factor of ten ?

Thanks for your help

Sincerely

ThommyW

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Furthermore, if I understood you right, the H2O data refere to the B-Dot equation (8.6) with 4 parameters:

phi = 1 - 2,303 A/(a^3 * I) (b - 2 ln(b ) - 1/b ) + B* I/2 + 2 C* I^2/3 + 3D* I^3/4

because 4 data sets are given. What is striking is, that all data given in the book are higher

by a factor of 10. What value is used ? Why is there a factor of ten ?

Thanks for your help

Sincerely

ThommyW

Hi ThommyW:

I'm not sure what the meaning is of the 4th set of CO2 parameters in the dataset- I'll see what I can find out. However, given that the values are all 0 in every GWB thermo data, I think you're safe to leave this as is.

As far as the coefficients for calculating the activity of water, the equation you list is correct (although it's equation 8.8 in the newer text, not 8.6). The parameters are given in figure 8.5 (p. 122), and I see exact agreement between this table and thermo.dat. Make sure you read the data correctly - parameters are only given for 25, 100 and 200C.

I hope that helps,

Tom

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Hello Tom,

Concerning the factor ten, I agree, the numbers were only written differently, thanks, it was my error.

Otherwise concerning parameters and equations, I am afraid you are in error:

In the new (blue) book Geochemical and Biogeochemical Reaction modelling the

equation 8.6 is

log(gamma) = aI + bI^2 + c*I^3

The values for neutral species (CO2(aq), O2(aq) etc. are given for 25, 100, 200 and 300°C only

in a table (on page 121), which contains only three parameters a,b, c.

So the data are given for the equation 8.6 (also three parameters), which is given for neutral species CO2(aq) etc.

That is why I wondered that there is one grid with only zero's .

(Is it a queston of simplicity for the program as for water there are 4 parameters ?).

In contrast to this the equation 8.8 is the one with four parameters and only refering to the activity of water

(I gave it above). In the table there are four parameters on page 122 and these are clearly refering to the equation 8.8.

Sincerely

Thomas Willms

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Hello Tom,

Concerning the factor ten, I agree, the numbers were only written differently, thanks, it was my error.

Otherwise concerning parameters and equations, I am afraid you are in error:

In the new (blue) book Geochemical and Biogeochemical Reaction modelling the

equation 8.6 is

log(gamma) = aI + bI^2 + c*I^3

The values for neutral species (CO2(aq), O2(aq) etc. are given for 25, 100, 200 and 300°C only

in a table (on page 121), which contains only three parameters a,b, c.

So the data are given for the equation 8.6 (also three parameters), which is given for neutral species CO2(aq) etc.

That is why I wondered that there is one grid with only zero's .

(Is it a queston of simplicity for the program as for water there are 4 parameters ?).

In contrast to this the equation 8.8 is the one with four parameters and only refering to the activity of water

(I gave it above). In the table there are four parameters on page 122 and these are clearly refering to the equation 8.8.

Sincerely

Thomas Willms

Hi Thomas:

I think you misunderstand my response- I'm agreeing that the equations for neutral species activity contain only 3 parameters, while the database shows a 4th. I don't think the existence of the 4th section (with all zeros) will affect your calculations in the slightest, but I am trying to find out why it is there.

I'll let you know when I hear something...

Regards,

Tom

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Hello Tom,

just to confirm my guess:

I suppose, that each of the gas solublities gas(aq) is defined by:

gas(g) --> gas(aq)

even if it is not written. How are they calculated

internally, especially N2(aq) ?

Haven't they been calculated on the basis of basic species because gases are not

belonging to those ?

Also, in one file I saw the Eh reaction had a value of

-86.... meaning based on O2(aq) in another one it is -83....

meaning that it refers to O2(g).

What is the usual form you are using, the one based on

O2(aq) because it is basic species or the other one?

What does GWB need actually?

Thanks

ThommyW

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Hi Thomas:

I suppose, that each of the gas solublities gas(aq) is defined by:

gas(g) --> gas(aq)

even if it is not written.

Reactions for gases are written in the 'gases' section towards the end of each database. For example, the following reaction for H2O vapor (called 'Steam' which is somewhat misleading at STP) is given as follows in thermo.dat:

Steam

mole wt.= 18.0152 g

1 species in reaction

1.000 H2O

2.2185 1.5043 0.7073 0.0056

-0.6552 -1.1499 -1.5293 -1.8257

How are they calculated internally, especially N2(aq) ?

Haven't they been calculated on the basis of basic species because gases are not

belonging to those ?

This is described in detail in section 3.3.7 on page 48 of the blue book. You'll want to read the rest of the chapter for context.

Also, in one file I saw the Eh reaction had a value of

-86.... meaning based on O2(aq) in another one it is -83....

meaning that it refers to O2(g).

What is the usual form you are using, the one based on

O2(aq) because it is basic species or the other one?

What does GWB need actually?

I'm not sure I understand your question- are you referring to a specific script and output file that you are using? Perhaps you can attach these...

Best regards,

Tom

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Hello Tom,

concerning part 1 of the anwers:

I know that there is a gas section, but I am speaking of the solubilities in the first part of the parameter file thermo.dat

which are generally based on the equation (and where no reactions are given)

X2(g) --> X2(aq)

--------------------------------------------------

* log k for eh reaction

-93.701 -86.003 -77.117 -68.972

-60.928 -54.559 -49.374 -45.037

* log k for o2 gas solubility

-2.6610 -2.8990 -3.0580 -3.1250

-3.0630 -2.9140 -2.6600 -2.4100

* log k for h2 gas solubility

-3.0240 -3.1120 -3.1440 -3.1120

-3.0520 -2.9420 -2.7300 -2.4400

* log k for n2 gas solubility

-2.9740 -3.1830 -3.3210 -3.3330

-3.1740 -2.9960 -2.7480 -2.4530

---------------------------------------------------------

As gases are no basic species in GWB, for this equation there is no ln(K) available directly.

That is why I asked. Now there are several possibilities:

1. Values are only implemented as values for each temperature, calculated elsewhere taken of a reference etc.

2. Values are calculated internally by combination of ln(K)'s of several reactions.

3. Values are calculated internally by the Gibbs energies of formation for each reactant.

concerning part 2:

Same thing, but I am not speaking of genereal procedures but of the reaction of the species N2 in case it has been

calculated by the second way given above (combination of reactions)

concerning part 3:

I am refering to the parameter files as e.g. the thermo.dat file.

By the way - as always - I looked at the book, but it was not clear to me from the book.

Your log(K) for Eh is identical with ours which is for H2(g) + O2(g) --> 2H2O.

Are you using the same equation although H2(g) and O2(g) are no basic species ?

Also values are different in different files. Why are there equations with different

basic species ?

in thermo_hmw.dat (as it seems : H2(g) + O2(g) --> 2H2O)

* log k for eh reaction

-91.0454 -83.1028 -74.0521 -65.8632

-57.8929 -51.6850 -46.7266 -42.6842

in thermo_phrqC (as it seems : H2(g) + O2(aq) --> 2H2O)

* log k for eh reaction

-92.2863 -87.5026 -83.1200 -78.3227

-73.9641 -69.9865 -66.3420 -62.9906

Why are there different equations (and values) in those files ?

In fact: I can sum up naealy all my questions (except for the last one) with one only question:

The values given in the very first part of the parameter file, giving Eh-values and solubilities etc.

are they basing on equations using directly or indirectly reactions with basic species or not ?

(which ones?)

Thanks very much

ThommyW

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Hi Thomas:

I know that there is a gas section, but I am speaking of the solubilities in the first part of the parameter file thermo.dat which are generally based on the equation (and where no reactions are given)

X2(g) --> X2(aq)

--------------------------------------------------

* log k for eh reaction

-93.701 -86.003 -77.117 -68.972

-60.928 -54.559 -49.374 -45.037

* log k for o2 gas solubility

-2.6610 -2.8990 -3.0580 -3.1250

-3.0630 -2.9140 -2.6600 -2.4100

* log k for h2 gas solubility

-3.0240 -3.1120 -3.1440 -3.1120

-3.0520 -2.9420 -2.7300 -2.4400

* log k for n2 gas solubility

-2.9740 -3.1830 -3.3210 -3.3330

-3.1740 -2.9960 -2.7480 -2.4530

---------------------------------------------------------

As gases are no basic species in GWB, for this equation there is no ln(K) available directly.

That is why I asked. Now there are several possibilities:

1. Values are only implemented as values for each temperature, calculated elsewhere taken of a reference etc.

2. Values are calculated internally by combination of ln(K)'s of several reactions.

3. Values are calculated internally by the Gibbs energies of formation for each reactant.

First note that the GWB v8 Reference manual (p. 248) says that of the O2(g), H2(g) and N2(g) solubility equations in the header file of thermo.dat, only the values for O2(g) are currently used. I'm not exactly sure how (I will find out), but note that the equilibrium constants for O2(g) in the header file:

* log k for o2 gas solubility

-2.6610 -2.8990 -3.0580 -3.1250

-3.0630 -2.9140 -2.6600 -2.4100

..are exactly the same as the constants for the O2(g) reaction in the Gases section:

O2(g)

mole wt.= 31.9988 g

1 species in reaction

1.000 O2(aq)

-2.6610 -2.8990 -3.0580 -3.1250

-3.0630 -2.9140 -2.6600 -2.4100

The latter is based on the mass action equation for the reaction: O2(g) = O2(aq)

In fact, all of the mass action equations in the Gases section are written either in terms of Basis species, or in terms of redox species (which can be thought of as a valence extension of the Basis). I believe this answers your summation question.

concerning part 2:

Same thing, but I am not speaking of genereal procedures but of the reaction of the species N2 in case it has been

calculated by the second way given above (combination of reactions)

See answer above...

concerning part 3:

I am refering to the parameter files as e.g. the thermo.dat file.

By the way - as always - I looked at the book, but it was not clear to me from the book.

Your log(K) for Eh is identical with ours which is for H2(g) + O2(g) --> 2H2O.

Are you using the same equation although H2(g) and O2(g) are no basic species ?

Also values are different in different files. Why are there equations with different

basic species ?

in thermo_hmw.dat (as it seems : H2(g) + O2(g) --> 2H2O)

* log k for eh reaction

-91.0454 -83.1028 -74.0521 -65.8632

-57.8929 -51.6850 -46.7266 -42.6842

in thermo_phrqC (as it seems : H2(g) + O2(aq) --> 2H2O)

* log k for eh reaction

-92.2863 -87.5026 -83.1200 -78.3227

-73.9641 -69.9865 -66.3420 -62.9906

Why are there different equations (and values) in those files ?

First, note that the equilibrium constants for the eh reaction in thermo.dat are based on the half-cell reaction as follows: 2H2O = O2(g) + 4H+ + 4e-

Second, when the PHREEQC data was converted to GWB format, the following notes were made (see header section):

* Log K values were calculated as a function of temperature using the

* analytic method from PhreeqC, unless data for this method was not provided.

* In that case, log K's were calculated versus temperture according to the

* van't Hoff equation.

* Redox reactions have been rebalanced in terms of O2(aq), rather than the

* electron e-.

* The reactions for redox couples have been rebalanced in terms of basis species,

* as expected by the GWB programs.

To reconstruct why the values are different, you'd need to start with the original PHREEQC data (as it comes with the software), and convert using the rules above.

I hope that helps,

Tom

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First note that the GWB v8 Reference manual (p. 248) says that of the O2(g), H2(g) and N2(g) solubility equations in the header file of thermo.dat, only the values for O2(g) are currently used. I'm not exactly sure how (I will find out), but note that the equilibrium constants for O2(g) in the header file:

* log k for o2 gas solubility

-2.6610 -2.8990 -3.0580 -3.1250

-3.0630 -2.9140 -2.6600 -2.4100

..are exactly the same as the constants for the O2(g) reaction in the Gases section:

O2(g)

mole wt.= 31.9988 g

1 species in reaction

1.000 O2(aq)

-2.6610 -2.8990 -3.0580 -3.1250

-3.0630 -2.9140 -2.6600 -2.4100

The latter is based on the mass action equation for the reaction: O2(g) = O2(aq)

Given the case, that in the lower block other data for solubility are entered than in the upper block: which data are used by GWB?

Regards,

Helge

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Given the case, that in the lower block other data for solubility are entered than in the upper block: which data are used by GWB?

Regards,

Helge

Hi Helge, Thomas:

The log K data for O2 solubility in the database header is combined with the log Ks there for the anodic oxidation of water to figure log K for the 2H2O <-> O2(aq) + 4H+ + 4e-. This is the electrolysis reaction the GWB uses internally. The O2 data is normally the same as the values in the gases section, but does not need to be.

As stated previously, the other gas solubility data in the header files are not currently used by GWB.

Similarly, the 4th header for calculating the activity coefficients for CO2 and other neutral species is a vestigial trait, and can be safely ignored.

I hope that helps,

Tom

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The O2 data is normally the same as the values in the gases section, but does not need to be.

If not, the parameter file is inconsistent.

To us it means that we have to enter precisely the same data in both sections, even though GWB doesn't require this.

Thank you for having made this clear.

Regards,

Helge

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