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An experience a lot of us might've had; a dry cell (not completely depleted) when left in an electrical device for long periods of time, has this viscous fluid coming out that usually corrodes the terminals of the battery.

I almost always find this fluid, present as a sorta thin film over the terminals and the casing of the battery.

I'm told that the Ammonium Chloride in the cell, being slightly acidic reacts with the zinc casing of the cell, which is why dry cells don't last long (My teacher mentioned this during our Electrochem. class, he didn't mention anything about that fluid I was talking about though). Could this fluid possibly the result of that reaction? What are its chemical constituents?

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  • $\begingroup$ Exactly which type of dry cell do you want to know about?All of them have different electrolytes.For example in alkaline cells it is potassium carbonate. $\endgroup$ – user14857 Sep 28 '16 at 5:05
  • $\begingroup$ @ZOZ the Le Clanché kind...... $\endgroup$ – paracetamol Sep 28 '16 at 14:26
  • $\begingroup$ ......now I'm not sure if it's Leclanché or Le Clanché..... $\endgroup$ – paracetamol Sep 28 '16 at 14:27
  • $\begingroup$ I doubt that's what you want.Because those cells used to be used in the 1800s.I wrote an answer regarding more recent cells. Lechlance is quite similar. $\endgroup$ – user14857 Sep 28 '16 at 14:49
  • $\begingroup$ Not really :-) en.wikipedia.org/wiki/Leclanch%C3%A9_cell $\endgroup$ – user14857 Sep 28 '16 at 17:10
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There are various kinds of dry cells.I will give some examples as to what is that oil-like fluid:

In zinc-carbon cell:

Zinc carbon cells have a short shelf life as the zinc is attacked by ammonium chloride. The zinc container becomes thinner as the cell is used, because zinc metal is oxidized to zinc ions. When the zinc case thins enough, zinc chloride begins to leak out of the battery. The old dry cell is not leak proof and becomes very sticky as the paste leaks through the holes in the zinc case. The zinc casing in the dry cell gets thinner even when the cell is not being used, because the ammonium chloride inside the battery reacts with the zinc. An "inside-out" form with a carbon cup and zinc vanes on the interior, while more leak resistant, has not been made since the 1960s.

In alkaline cells:

Technically, that white fluffy corrosion that develops at the ends of the battery (most often the negative end) is called potassium carbonate.

All batteries will slowly gradually self-discharge over time. This will occur whether they are setting on the shelf (a much slower process) or installed in a device (which often occurs much quicker) – and dead batteries will eventually leak.

Very high temperatures can also cause batteries to rupture and leak (e.g. in hot car during the summer).

The “alkaline” of the battery is potassium hydroxide (it’s the alkali equivalent of acid’s hydrochloric acid), and this will leak out, forming a white “fluff” of potassium carbonate, typically on the negative end of the battery cell – because apparently the positive end is vented better.

So the reason for the cell-corrosion varies with the type of the cell.

Read the Wikipedia page to know about the composition of electrolytes of different dry cells.https://en.wikipedia.org/wiki/Dry_cell

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  • $\begingroup$ Would you also happen to know the product of the reaction between the ammonium chloride and the Zinc canister? I vaguely recall some source telling me it includes the complex [Zn(NH3)4]2+, but I can't find sources backing that up....great answer by the way.... $\endgroup$ – paracetamol Sep 28 '16 at 16:10
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    $\begingroup$ Yes you are correct.See en.wikipedia.org/wiki/Metal_ammine_complex that's the most probable product as far as I know! $\endgroup$ – user14857 Sep 28 '16 at 17:08

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