range of thermodynamic data

[Sheila Roberts]

I've been generating diagrams and doing speciation calculations at temperatures at and above 200 degrees. I notice that as you increase temperature, there are fewer aqueous species that appear in the output. Is there a way I can see what the temperature range for a given aqueous species is?

[Brian Farrell]

Hi Sheila,

 

The best way to see this information is to look at the thermo dataset being used by the GWB app. Go to File - View and select the thermo dataset from the list of files to open it in TEdit (GWB10 and later) or a text editor like Notepad (GWB9 and earlier). When you're looking at an entry for a particular species or mineral, you'll see at the bottom a block of 8 numbers. These are the log Ks for the reaction at the principal temperatures of the thermo dataset (check the top of the dataset to see what they are). If you see a value of 500, that indicates there is no data available at that particular temperature.

 

A species will not be loaded in a calculation if data does not exist for the temperature (or temperature range) of the simulation. The software will fit the log Ks to a temperature polynomial so that it can interpolate between data points. It will not extrapolate outside the temperature range, however, unless you enable the "extrapolate" option. You should be careful with this option.

 

Hope this helps,

 

Brian Farrell

Aqueous Solutions LLC

[Christoph]

Hi Brian, Hi Sheila,

 

is the only way to show the coefficients for the temperature polynomial calculating the equilibrium constants to use the Rxn module and conduct a calculation?

 

 

Kind regards,

Christoph

[Brian Farrell]

Hi Christoph,

 

Yes, you should use Rxn to calculate the temperature polynomial.

 

Cheers,

Brian