How to calculate of the number of monocationic millimoles? If I have concentrations of: $SiO_2$, $TiO_2$, $K_2O$, $MgO$, $MnO$, $Na_2O$, etc.
How can I get $Na^+$, $Mg^{2+}$, $Mn^{2+}$ ..?
This is part of an intent to calculate the weathering intensity scale suggested by Meunier et al. (2013), but it is a doubt suitable to any kind of use of oxides, so post it apart from it. See a related WIS question.
Reference: Meunier, A.; Caner, L.; Hubert, F.; El Albani, A. and PrĂȘt, D. (2013). The weathering intensity scale (WIS): An alternative approach of the Chemical Index of Alteration (CIA). American Journal of Science, 313(2), p.113-143. doi: 10.2475/02.2013.03