P6_anim_zm_magic_box ╔══════════════════════════════════════════════════════════════════════════════════════════════════════════ Let say, the mixture of potassium hexacyanoferrate(III) and phenolphthalein is the rust indicator. And we use to detect the rusting of an iron nail. And The end result is: the tip, head location with the nail surface blue coloration; the straight area appear... https://tropicallimos.co.uk