The formation of extractable species occurs
step by step, until his hydration degree becomes
comparable with the hydration environment of
PEG-rich phase from extraction system. In
function of the stability of metallic species formed
with phase-forming anion (βMAy− m) and with
inorganic extractant (βMXnx−), the following three
situations are possible (Laura Bulgariua, at. el.,
2008).