Recently I ran out of dish washing detergent, so I decided to pick up one of the recipes online, to make my own "ecological" dish washing detergent alternative.

The recipe was:

  1. Mix ingredients:
    1. 400ml of water
    2. 200mg of kitchen salt
    3. 100ml of vinegar
    4. juice squeezed from 3 lemons
  2. boil for 10 minutes

After I stopped boiling and left the mixture to cool down, the fluid turned dark gray. Bottom of my stainless steel pot turned black. Here is a photo of it (after I did some scrubbing, but you can still see black on the side): enter image description here

What happened? (What chemical reaction?) Additionally, are any of the formed substances known to be toxic?

  • 1
    $\begingroup$ What is your pot made of? $\endgroup$ – Nilay Ghosh Sep 16 '19 at 14:54
  • 2
    $\begingroup$ In no way would the chemicals used produce a detergent. Wherever you got this information should be considered an unreliable source of information. $\endgroup$ – DrMoishe Pippik Sep 17 '19 at 0:48
  • 2
    $\begingroup$ @Alchimista why do I expect they turn something to be used for cooking in something toxic? Because they were used in pretty high dose (salt especially) and they reacted with the pot surface. So far no one was able to tell what reaction took place. $\endgroup$ – user2449761 Sep 17 '19 at 11:33
  • 4
    $\begingroup$ So, as usual, some power users just didn't want us to answer to a valid question.What is wrong with this question? $\endgroup$ – SteffX Sep 17 '19 at 14:45
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    $\begingroup$ I think there's interesting chemistry here -- mixing vinegar and/or lemon juice with salt will produce an acid environment with chloride ions, which attacks metals a lot more readily than the weak acids or the salt alone. $\endgroup$ – jeffB Sep 18 '19 at 17:24

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