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# What are the units that "Minerals in system" are reported in in the output file from React?

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Hello, I ran a very saline water that was supersaturated with respect to a few minerals. I allowed them to precipitate as I cooled the water. The output text file from React shows what and how much precipitated in the "Minerals in system" portion of the file for each temperature step. The units are: moles, log moles, grams, and volume.

Are these reported per kg of solvent? When I plot the results using Gtplot with temp as the X-axis and Minerals (g/kg) as the Y-axis, I get smaller values than in the output text file. The solvent mass is 1 kg and the solution mass is much greater (around 1.3-1.4 kg). Thus, I assume that the results in the output text file are per kg of solvent, and those in the Gtplot are per kg of solution.

Is this correct?

Thanks,

Andrew

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Hello Andrew,

The amount of mineral reported in the output text file is the amount of mineral in the whole system and not per kg of solvent. The g/kg unit in the Gtplot configuration dialog is grams of mineral per kg of solution. If you divide the mineral mass(g) by the solution mass(kg) in the same block from the text file, then it should match the value displayed in Gtplot for that step. For example, I ran the attached input file and looked at the results in the output text file at step #100. The mass of anhydrite is 0.03558 grams and the solution mass is 1.3669 kg, dividing the anhydrite mass by solution mass is 0.025973 g/kg. I copied the data from the Rxn progress vs. Minerals plot and pasted it Excel to see the grams of Anhydrite per kg of solutions at step 100. It shows the 0.0259736915828 g/kg.

Please note with your React_output.txt file, you should see two Xi = 0 text blocks any time an initial system contains supersaturated minerals and precipitation is not disabled. The first block shows you the metastable equilibrium state of your aqueous speciation after you have initialized your run, where no supersaturated minerals have been precipitated.

Hope this helps,
Jia Wang

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• 1 month later...

Hi Jia,

Thanks very much. Makes sense.

Cheers,

Andrew

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