8. Electrolysis of table salt solutions with anodes made of Cola two can metals

Experiment 1 : Salt water and one drop of universal indicator solution (UI) are electrolysed in a the cavity of a blister packing.  A strip of sanded cola can metal (Fe) is used as negative electrode, its closure (Al) as positive electrode. A strong flow of gas bubbles is observed at the Fe cathode. The green colour of UI turns to violet (alkaline).
                      Reduction:  4 H₂O(l)  + 4 e^- --> 2 H₂(g) + 4 OH^-(aq)
At the Al anode less gas bubbles come out, the green colour of UI turns to red (acidic).
                     Oxidation:           2 H₂O(l)  --> O₂(g) + 4 H⁺(aq) + 4 e^-
                    Redox reaction:    2 H₂O(l)  --> 2 H₂ (g) +  O₂ (g)
Verification of this interpretation:
The liquids around anode and cathode are mixed after the end of electrolysis: The colours of UI return to green again. This proves that equivalent quantities of hydroxide and of oxonium ions have developed during cathodic reduction and anodic oxidation. These ions neutralised each other during mixing
Experiment 2 (2 and 3)
In this experiment the electrodes are exchanged: The tin (Fe) is used as the positive electrode, the closure (Al) as negative electrode. Both are dipped into the cavity of the blister packing with salt water + UI again.
Gas bubbles are observed at the negative electrode (Al). The colour of the UI changes to violet.(alkaline).
                    Reduction: 2 H₂O(l)  + 2 e^- -->  H₂(g) + 2 OH^-(aq)
No gas is observed at the positive electrode (Fe), the UI remains green.
               Oxidation:                    Fe(s)  --> Fe²⁺(aq) + 2e-
            Total reaction:   2 H₂O(l) + Fe(s) -->  Fe²⁺(aq)  +  2 OH^-(aq) + H₂(g).
Verification of this interpretation:
3: The electrolysis is repeated without UI. The liquids around anode and cathode are mixed:
     A green slimy precipitation appears:  Fe²⁺(aq) + 2 OH^-(aq) --> Fe(OH)₂(s)
     By adding drops of diluted sulfuric acid this precipitation disappears:
                                              Fe(OH)₂(s) + 2 H⁺(aq) –neutralisation-->  Fe²⁺(aq) + 2H₂O
Drops of KMnO₄ solution lose their colour showing that Fe²⁺ ions were present:
       5 Fe²⁺(aq) + MnO₄^-(aq) +  8 H⁺(aq) ---direct redox reaction -->  5 Fe³⁺(aq) + Mn²⁺(aq) +  4 H₂O
In order to test for iron(III) ions two drops of the solution are transferred into two cavities of a blister. One drop of potassium hexacyanoferrate(II) solution is added to one sample: A blue precipitate is observed. One drop of ammonium thiocyanate solution is added to the other sample. A red brown colour appears.