pH-Eh diagrams about Fe-O-C-H

[Xiluo]

1: Why does the species of "iron salt of acetate" disappear abruptly while the temperature become above 25 degree C ? ( Condition:a[main]=10E-10,a{CO3

 

[2-]}=10E-10, P=1atm.)

 

2: There is species of "FeO©" during the calculation . What does the "©" mean ? What's the difference between FeO© and wustite ?

 

 

 

3: Why those FeOOH species are not in the fields ? Such as alfa-FeOOH (goethite), gamma-FeOOH (lepidocrocite), beta-Fe(OOH) (akaganite).

Fe_O_H_C.ac2

[Tom Meuzelaar]

Hello:

 

 

1: Why does the species of "iron salt of acetate" disappear abruptly while the temperature become above 25 degree C ? ( Condition:a[main]=10E-10,a{CO3[2-]}=10E-10, P=1atm.)

 

In thermo.dat, this species only has log K constants defined for 0 and 25C. In Act2, GWB will not extrapolate log K values outside temperature ranges for which they are defined.

 

 

2: There is species of "FeO©" during the calculation . What does the "©" mean ? What's the difference between FeO© and wustite ?

 

I don't know what the "©" notation refers to, but Wustite has a small Ferric iron component, whereas FeO© is composed entirely of Ferrous iron.

 

 

3: Why those FeOOH species are not in the fields ? Such as alfa-FeOOH (goethite), gamma-FeOOH (lepidocrocite), beta-Fe(OOH) (akaganite).

 

As far as I can tell, these species do not exist in thermo.dat. You would need to add this data before it can be considered on your Eh-pH diagram.

 

I hope that helps,

 

Tom Meuzelaar

RockWare, Inc.

[Xiluo]

Hi,

 

1.Can I calculate the log K constants of "iron salts of acetate" using GWB and add them into the database ?

 

2.The species is "FeO(c)" ,not "FeO©". And what does the "(c)" mean ?

 

3.How can I get the data of FeOOH species and add them into thermo.dat ?

 

I am a new user of GWB and English is a foreign language to me . Sometimes I just can't express myself clearly. I hope that it will not disturb you for

understanding what I said.

 

THANK YOU

[Tom Meuzelaar]

Hello:

 

1.Can I calculate the log K constants of "iron salts of acetate" using GWB and add them into the database ?

 

Sure- you can simply modify thermo.dat by opening it in a text editor such as Notepad and adding the log K values directly. I strongly recommend that you rename the database before you begin editing it.

 

2.The species is "FeO(c)" ,not "FeO©". And what does the "(c)" mean ?

 

That is an artifact of the forum- if I type "(" followed by "c" followed by ")" the forum expresses this as ©. Regardless of how it is expressed, I still do not know what it stands for. Maybe "crystalline"? I'm only guessing- perhaps another user knows about this.

 

 

3.How can I get the data of FeOOH species and add them into thermo.dat ?

 

There is an entry for Goethite (FeOOH) mineral in thermo.dat. To find thermodynamic data for species and minerals not in the database, you will need to search the literature. Sometimes a user will respond if you post a request for data in this forum, but more often than not, you will need to look for this information yourself.

 

I hope that helps,

 

Tom Meuzelaar

RockWare, Inc.

[Xiluo]

I try to modify thermo.dat ,but it doesn't work ,I still can't see the "iron salts of acetate" at higher temperature such as 45 or 65 degree C. Please tell me how to modify the thermo.dat if I want to add the data of "iron salts of acetate" at 45 or 65 degree C just using the data of which at 25 degree C

[Tom Meuzelaar]

I try to modify thermo.dat ,but it doesn't work ,I still can't see the "iron salts of acetate" at higher temperature such as 45 or 65 degree C. Please tell me how to modify the thermo.dat if I want to add the data of "iron salts of acetate" at 45 or 65 degree C just using the data of which at 25 degree C

 

Hello:

 

You can either add the same log K value for the higher temperatures in thermo.dat, or you can turn on the Extrapolate variable in the Config menu in SpecE8. In the latter case, you are not actually modifying the database- the software simply extrapolates the log K value to a temperature range outside that specified by your data in the database.

 

Best regards,

 

Tom Meuzelaar

RockWare, Inc.