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Chemistry Questions: What do you get from combining salt, white vinegar and cupric oxide? And what can be done with it? Answered

In my enameling work, I sometimes use a mild homemade pickling solution to remove firescale (cupric oxide) from copper. The pickle is a saturated solution of white vinegar and kosher salt, kept hot in a Crock Pot. After heating the copper pieces in a kiln, a layer of cupric oxide forms on the surface, which is then dissolved in the salt/vinegar solution. After a while, the solution turns a lovely blue color from the dissolved copper.
If I forget to put the lid on the pot, eventually the solution evaporates, leaving pretty blue crystals that look a bit like copper sulfate.
So, what have I got here? I don't want to just dump it due to the copper content. I'd like to figure out something to do with it, but first I need to know what it is. I'm thinking it might make a good electroplating solution, but that's just a guess.


You wind up with Copper Acetate and salt - the water has evaporated.  Maybe you could use it in your enamel work for items that won't be used with food or worn on the skin?  Alternatively you could try growing the crystals and encase them in resin for some neat jewelry.

So the salt doesn't participate in the reaction at all? That's kind of disappointing. I wonder why it's in the solution, then.
I like the idea of growing the crystals. They are quite pretty, and I bet they'd be even prettier if I was growing them on purpose.

It takes a lot to react NaCl with something.  It might help the reaction though as an accelerant or might play some other part, or it might not do anything at all.  You can remove copper oxide with just vinegar and no salt, but a lot of cleaning recipes (like how to clean a copper pot) include salt as a mild abrasive from what I know.  You should probably be glad NaCl isn't reacting with anything because it might be more "exciting" than what you'd care to have in your house.  ; )

Good point. I have been known to enjoy playing with metallic sodium (under controlled conditions), but a studio full of free chlorine would kind of suck.

Salt will raise the boiling point of the liquid, and may well cut down on acid fumes (couldn't be sure though). Also, when you've got ions in solution you've got more than one option for salts. E.g. copper (II) chloride is much more soluble (in water) than acetate, which may well be why the salt is in there.

The blue colour will be hexaqua-copper, what it's countered with in the crystalline form I'm not certain of, but I'd go with Angry' on the acetate.


Cool. Thanks very much for the insights.
I really wish I had paid more attention in Chemistry class, but there was this girl in the next row....