x. Note that we assume that the [extractant] greatly surpasses [metal], which allows for * ini = 2.24 M found for the extractant:acid stoichiometry changes in the metal free system, as shown in Figure . These data support the changes to aggregation that occur before and after the CMC. At the lowest acid concentration, the metal is extracted as a relatively "ideal" metal-ligand complex of M(DMDOHEMA) 4 (NO 3 ) 3 . Note that in the metal-free extraction under the same conditions, there is a near 1:1 ratio of HNO 3 :extractant, which is consistent with the stoichiometry when Am 3+ /Eu 3+ is extracted as the metal replaces one HNO 3 in the stoichiometric ratio. As acid concentration is increased and more acid and water is extracted into the organic phase, aggregation of the extractants occurs, which decreases the stoichiometric ratio of the metal:extractant. At the CMC the acid concentration dependent aggregation behavior stabilizes and as such the metal:extractant ratio approaches a constant value above the critical acid concentration.