Question about PHREEQCI

["Michele Y Crouse" <mcrouse@xxxxxxxx>]

----- Forwarded by Michele Y Crouse/WRD/USGS/DOI on 08/06/01 01:04 p.m.
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                      "Kaoru Masuda"                                                                
                      <k-masuda@xxxxxxxxxxx         To:      <h2osoft@xxxxxxxx>                     
                      elco.co.jp>                   cc:      <seik@xxxxxxxxxxxxxxxxxx>              
                                                    Subject: Question about PHREEQCI                
                      08/05/01 11:42 p.m.                                                           
                                                                                                    
                                                                                                    



Dear Sir,

I am a user of PHREEQC interactive.  And I have some questions
about the calculation.
Would you please transfer this e-mail to someone who knows it well?

I want to calculate CO2 gas dissolution into water solution.
For example, If 350ppmV-CO2 gas phase exists with a solution of pH=7,
I think that the *.in file must be as follows;

SOLUTION 1
 temp 25.0
 pH 7
 pe 4
 redox pe
 units mg/kgw
GAS_PHASE 1
 -pressure      1
 -volume        1
 -temperature   25
 CO2(g) 0.00035
END

The result of the calculation with abobve *.in file shows that
total C in the solution is 1.4E-5 mol/L and pH is 5.6.
I think this result is reasonable.
However, by replacing the volume to 1000 instead of 1, the
result shows that total C is  1.4E-2 and pH=4.1.
On the other hand, by replacing pressure value to 1000 instead of 1.
total C is 1.4e-5 and pH=5.6.
I think that the solubility has not be changed with volume
by Henry's Law.
Do I have some misunderstanding about this ?

Please give me some comments about it.

Yours Sincerly,

Mr. KAORU MASUDA
Kobe Steel, Ltd.
1-5-5, Takatsuka-dai Nishi-ku
Kobe 651-2271
JAPAN
Tel  Japan-78-992-5733
Fax Japan-78-992-5547