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In my school there are jars which are turned into Lechlanché cells. Basically the cell has aqueous ammonium chloride solution as the electrolyte which is obviously transparent in the beginning. The electrodes used are zinc and the second electrode is a porous pot which has a carbon rod and crushed manganese(IV) Oxide. The electrolytes in cells which have been used for a long time have turned blue. I want to know where this colour is coming from. Because ammonium salts are colourless, zinc complexes cannot show colour due to d-d transition and I have never seen a blue coloured manganese compound. So what is it that is forming due to which the solution is turning blue?

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  • $\begingroup$ How pure is the zinc? How much copper (-> deep blue ammonia complex) is in it? $\endgroup$ May 12, 2017 at 18:40
  • $\begingroup$ I think this is due to the colour ammoniated electrons (blue) $\endgroup$ May 12, 2017 at 19:17
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    $\begingroup$ Solvated electrons in water solvent? Not sure they are blue in water or would last long enough to be seen without special equipment. $\endgroup$ May 12, 2017 at 19:28
  • $\begingroup$ Not sure. We use zinc rods so I don't think there will be much impurities in the rod which could turn the solution deep blue. $\endgroup$ May 13, 2017 at 2:52
  • $\begingroup$ Yes , I also think that the colour couldn't be due to ammoniated electrons because there is water in excess. But then again I am not completely sure. $\endgroup$ May 13, 2017 at 2:54

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