*3.3. Target Evaluation*

The fraction of liberated grains decreases for quartz + silicates by about 20%. In all P-containing phases, locking increases drastically (up to 98%) in all inorganic acid residues. Contrasting, in the original material, these groups were much more liberated, by up to 55%. The same is true for Fe-phases, although the original degree of locking was higher in this group (75% up to 97%). Comparing locking values for quartz + silicates of pre-treated digestion residues with non-pre-treated digestion residues, these grains reveal reduced degrees of locking in residue (successful digestion of grains previously associated with quartz + silicates) for HCl. Thus, pre-treatment enables access to complex particles where access is desired. Quartz + silicates locking values for their preferred partner (1–5 wt% P-phases) show a decrease in locking values (pre-treated ash yields a residue with less complex quartz + silicates particles).

Locking increases in all phases between original SSA and residue. This lends room to the hypothesis of complex mechanisms leading to ternary<sup>+</sup> particles. Keeping in mind that about 40 wt% of the material were already extracted, it is not surprising to find complex particles in the undigested residue.
