Question

How to making aluminium metal solution to back titration method?

Answer 1

Reactions taking place during titration are - at first

Al3+ + EDTA4- → AlEDTA-

(this is the slow part), then

Zn2+ + EDTA4- → ZnEDTA2-

which is fast enough for use in direct titration.

Finally, we should mention reaction that is responsible for the end point detection - that is, precipitation of the zinc ferrocyanide:

Zn2+ + Fe(CN)64- → Zn2Fe(CN)6