I ran a simple reaction path model reacting quartz, k-feldspar, and muscovite with dilute solution. When I add the minerals in the reactant tab as volumes (cm3) the saturation indices in the output file in early steps do not match what it plotted. However, when I convert the volumes to mass (g) by hand and add the minerals in the reactant tab as mass the saturation indices in the output file match the plot. The plot is the same for both volume and mass added cases but the output files are not. I am attaching the two react files. In both cases K-feldspar reaches saturation at x=0.1 according to the plot, in the case where mineral are added by mass the output matches the plot, but in the case where the minerals are added as volume the output file shows k-feldspar, quartz, and muscovite saturated in the first step.
addition_mass.rea
addition_volume.rea