"Maclnnes"

[IliasBouchkira]

Dear all,

i'm working on the dissolution of tricalcium phosphate in phosphoric acid solution, when i make the simulation, i have as results of activity : "Maclnnes", what does it mean please? i'm wondering if it refers to an error or somthing? in this case what can i do to avoid it?

Thanks in advance,

[dlparkhurst]

MacInnes is a scaling option for activity coefficients available with Pitzer databases, pitzer.dat for example.

Single ion activity coefficients are unmeasurable. Thus, asserting the activity of any ion requires a convention; this includes pH. The MacInnes assumption is that the activity coefficient of K+ and Cl- are equal in KCl solutions. For any solution, the activity coefficients by using the activity coefficients of K+ and Cl- in an assumed solution of equivalent ionic strength.

You can turn off the MacInnis assumption, see PITZER keyword data block. The saturation indices of minerals and mean activity coefficients of salts are unaffected by the assumption. Only the individual activity coefficients and activities of ions are affected.