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Andrew Wigston

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  1. Hi Jia, I have a follow up question. I ran the same water as above and did the same swap (dolomite for H+) but this time I raised the temperature from 25C-120C. The amount of dolomite at 120C in the system (0.012976 moles, as specified in the "Minerals in system" portion of the output file) is more than the initial amount (0.01222 moles). The solution mass is only slightly different (1.2224 vs. 1.2222 kg). I was under the impression that when I swap dolomite for H+ that no dolomite precipitates or dissolves. Can you shed some light on what is going on? Thanks, Andrew B4
  2. Warning ā€“ long post! My question concerns how to determine the pH and partial pressure of CO2 (PCO2) in brine samples. I tried two different methods: 1) swapping a carbonate mineral in in place of H+; and, 2) titrating in CO2(g) till I get a saturation index (SI) of 1. I am wondering which is the most appropriate method (and some other questions). Background: I have a number of samples from a brine. The water is an Na-Cl type brine: Na+ ~70,000 mg/L (~3.2 molal) and Cl- ~115,000 mg/L (~3.5 molal) (there is ~ a few % charge imbalance). The pH was measured in the lab. The formation
  3. Hi Jia, Thanks for the clarification. Andrew
  4. Hi Jia, Thanks for your answer. I misunderstood the Elemental composition section of the output file. I thought it was the composition of the system after I had made changes to it (e.g. swapping in quartz for SiO2(aq). However, I believe it is just the original composition ā€“ but in elemental form as you noted. Is this correct? I understand from your answer that I can get this info in Gtplot. And to see if Iā€™m really getting this: Assuming that the solvent mass is 1 kg, I would think that the moles in the In fluid section would be molal (i.e. moles per kg of solvent), correct?
  5. Hello again, Follow up question to my initial post (and happy holidays!) In my work I would like to compare the concentration of elements in a fluid before and after I make changes to the system. For example, I would like to see how the concentration of dissolved silicon changes due to swapping in quartz in place of SiO2(aq). I understand that I can go to the Elemental Composition section of the text file output and get data there, which includes total moles, and in the fluid moles, and mg/kg (and there is also a bit for sorbed concentrations). My understanding from your answer
  6. Hello, newbie user here, so please excuse my ignorance regarding what I think may be a simple problem. I am using GWB 14. I have a sample of brine. It has a lab-reported value for Na of 83,900 mg/L. I entered it and all the other analytes in GSS (I did not enter a solvent mass). Out of curiosity, I converted it to some of the various other units available and here is what I get (using the thermo.tdat database) mg/L mg/kg Mol (no units listed)
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