lvsoar

Hi Tom, Thanks for your reply. I have a follow up question on (3). If I set Cu activity in the system as 1e-6 and use "thermo" database to plot, how are the boundaries of CuOH+ vs Tenorite and CuOH+ vs Cuprite defined? Does the program assume the CuOH+ to be 1e-6 M when calculating the boundaries? Or, it will speciate Cu++ and CuOH+ at certain pH value and used the real activity of CuOH+ (say 1.5e-8 M) to calculate the boundaries? Peng

Hi, I have 3 basic questions about ACT2: (1) If I want to plot a ACT-ACT diagram on Cu, is that true that for the diagram species I can only input total activity instead of molality? I see that it only gives me the choice of activity or log activity. (2) If I input the total activity of 10^-3 for Cu, is the 10^-3 including both the dissolved and solid phases? (3) How is the boundary between aqueous species and solid phases defined in ACT2? Garrels and Christ, defined the boundary as the point where the “sum of the activities of the ions in equilibrium with the solid exceeds some chosen value”. They chose 10^-6 as a default value on the basis that if it is less than this value, the solid will tend to behave as an immobile constituent in the environment. My question is whether the boundary is defined following Garrels and Christ (boundary at total dissolved Cu to be 10^-6) or to be the line where mineral precipitation begins? Thanks, Peng