Two analytical methods, colorimetry and WDS, were
employed by the instructors to confirm the percentage of
aluminum in the commercial foil. Colorimetry is based on the
color change due to the reaction between Eriochrome Cyanine
R (ECR) and aluminum ions. This technique was only
employed to confirm the results found with stoichiometry,
and it is not intended to be carried out by students. Full
experimental details for this step are given in the student
handout in the Supporting Information. Figure 2 shows a series