[trianluz]

I did a simple electrolysis experiment with copper as both the anode and the cathode through a solution of salt water.  The result(after stirring together) was a brown precipitate and a very faint yellow solution.  I assumed the brown precipitate was Copper(II) Chloride in its anhydrous form.  I decanted it, washed it, and dryed it in an oven(300^o F).  What I have now is a dark brown(darker than rust) powder.

Is this Copper(II) Chloride?  I thought that it would become hydrated if i let it exposed to the atmosphere.  It has been two days now.  I see no change.  Might it be Copper Hydroxide?  Perhaps the Sodium Hydroxide produced in the reaction reacted with the Copper Chloride that should have been produced?

2NaCl(aq) + 2H₂O(l) + Cu(s) + 2e^- -> CuCl₂(s?) + 2NaOH(aq) + H₂(g) + 2e^-

[Borek]

I assumed the brown precipitate was Copper(II) Chloride in its anhydrous form.  I decanted it, washed it, and dryed

Anhydrous form in the solution?

[hmx9123]

Burn some of it in a bunsen or alcohol burner.  It should burn with a blue flame if it is copper I or II chloride.

[trianluz]

I assumed the brown precipitate was Copper(II) Chloride in its anhydrous form.  I decanted it, washed it, and dryed

Anhydrous form in the solution?

That's what threw me off.  I thought that it should produce the hydrated form since it is in water.  (Edit: Perhaps the rate at which the compound is being produced affects this?  The volage was around 12.8 V)Perhaps it is some other copper compound, but I still think the only thing it sould be is chloride since the anode was copper and chlorine gas was not produced(as it would have if the anode was unreactive such as graphite).

I will try a flame test, but does it work even if the compund is not split up into ions(as in water)?

[hmx9123]

Copper I chloride is insoluble in water.  When pure, it's a white powder.  When old, heated or impure, it can range anywhere from green to brown.  That may be what you have.  Copper II chloride is very soluble in water and is hygroscopic.  If your stuff is a dry powder, I'd bet copper I if it burns blue.  Copper II gives a green-blue flame test as where copper I chloride is more of a blue green.  The difference is almost indistinguishable.

[woelen]

It is a common misconception that electrolysis of NaCl-solution only gives copper (II) at the anode. What you actually obtained is an impure copper (I) compound. At the very high concentration of chloride, the copper (I) chloro complex is highly stabilized. The formation of a chloro-copper (I) complex is favored over the formation of copper (II).
 
What happens is that the anode goes in solution, one electron is absorbed by the anode, due to the applied voltage:

Cu - e + 2Cl(-) ---> CuCl2(-)

At the cathode, you get hydroxide from the water (and hydrogen):

2H2O + 2e --> 2OH(-) + H2

The hydroxide reacts with the CuCl2(-), giving hydrous Cu2O, which is yellow/orange.

As a side reaction you will also obtain a small amount of copper (II) and the oxygen from the air also oxidizes some of that. This copper (II) is blue and also is mixed into the hydrous Cu2O precipitate. For this reason, you do not obtain a nice bright yellow/orange precipitate, but a dirty yellow/brown color.

On rinsing, drying and heating, you get an impure mix of Cu2O and CuO (and also remains of sodium and chloride ions, trapped into the slimy precipitate). This mix is dark brown and is not hygroscopic.

[hmx9123]

BTW, are you trying to make copper(II) chloride or copper(I) chloride or are you experimenting with electrolysis?  There are more convenient preps than electrolysis that you can do at home if synthesis is your goal.

[trianluz]

It is a common misconception that electrolysis of NaCl-solution only gives copper (II) at the anode. What you actually obtained is an impure copper (I) compound. At the very high concentration of chloride, the copper (I) chloro complex is highly stabilized. The formation of a chloro-copper (I) complex is favored over the formation of copper (II).
 
What happens is that the anode goes in solution, one electron is absorbed by the anode, due to the applied voltage:

Cu - e + 2Cl(-) ---> CuCl2(-)

At the cathode, you get hydroxide from the water (and hydrogen):

2H2O + 2e --> 2OH(-) + H2

The hydroxide reacts with the CuCl2(-), giving hydrous Cu2O, which is yellow/orange.

As a side reaction you will also obtain a small amount of copper (II) and the oxygen from the air also oxidizes some of that. This copper (II) is blue and also is mixed into the hydrous Cu2O precipitate. For this reason, you do not obtain a nice bright yellow/orange precipitate, but a dirty yellow/brown color.

On rinsing, drying and heating, you get an impure mix of Cu2O and CuO (and also remains of sodium and chloride ions, trapped into the slimy precipitate). This mix is dark brown and is not hygroscopic.

Ah, that seems to make sense now.

And my goal is indeed to make some CuCl₂ for copper plating.  How would I go about doing this?

[hmx9123]

This prep comes from chemicals you can easily obtain at the store, so bear with me:

- Buy some copper (II) sulfate fertilizer at your lawn and garden shop.  Usually sold as sulfate of copper.
- Buy some potassium carbonate from your local grocery store/home depot/pool center.  It's sold as pool pH increaser.  You can use baking soda, but the potassium carb works better
- Make a solution of each and add the K carb to the cu solution--there will be a little CO2 released as the copper sulfate solution is acidic.  This forms a blue precipitate--filter this out and save it
- Buy some muratic acid (HCl) from your hardware store.
- Add the muratic acid to the blue ppt you obtained in the last step (which is basic copper carbonate).  This generates a lot of carbon dioxide and will leave you with copper (II) chloride in solution.  Evaporate the water and you'll be left with the solid copper (II) hydrate.

This is bucket scale chemistry--it works on very large scale, so you can make pounds of CuCl₂ for just a few dollars.

[trianluz]

This prep comes from chemicals you can easily obtain at the store, so bear with me:

- Buy some copper (II) sulfate fertilizer at your lawn and garden shop.  Usually sold as sulfate of copper.
- Buy some potassium carbonate from your local grocery store/home depot/pool center.  It's sold as pool pH increaser.  You can use baking soda, but the potassium carb works better
- Make a solution of each and add the K carb to the cu solution--there will be a little CO2 released as the copper sulfate solution is acidic.  This forms a blue precipitate--filter this out and save it
- Buy some muratic acid (HCl) from your hardware store.
- Add the muratic acid to the blue ppt you obtained in the last step (which is basic copper carbonate).  This generates a lot of carbon dioxide and will leave you with copper (II) chloride in solution.  Evaporate the water and you'll be left with the solid copper (II) hydrate.

This is bucket scale chemistry--it works on very large scale, so you can make pounds of CuCl₂ for just a few dollars.

Thanks!  This is very informative.  Since I just need it for copper plating, I think I can settle for just buying the Copper(II) Sulfate and using that.

Just out of curiocity, is it possible to make it through electrolyis?  Perhaps you would need an ion exchange membrane to prevent the OH from reacting.

[hmx9123]

I didn't know if you were looking for the chloride for some specific reason when electroplating or not.  BTW, if you get the copper(II) sulfate from the garden shop, make sure you recrystallize it first--it's a little dirty.

I'm sure it's possible to make copper(II) chloride through electrolysis, but at home, it may be very difficult to do.  There are a lot of copper species, such as copper(I) chloride, copper(II) chloride, copper oxychloride, and both copper oxides to worry about.  Kind of messy.

[Borek]

And my goal is indeed to make some CuCl₂ for copper plating.

Can't you use CuSO₄ directly? (which is more or less what hmx is talking about )

[billnotgatez]

I know this is a little late in posting, but you might find some ideas here.

http://sci-toys.com/scitoys/scitoys/echem/echem.html

http://www.funsci.com/fun3_en/electro/electro.htm

[aliphatic]

I know this is incredibly late in posting, but this is a top search result in google and I want to add a few things for the next guy who clicks looking for answers.

A: Unless you have a specific reason to, don't bother converting copper sulphate to cupric chloride for electroplating purposes - copper sulphate can be used itself.

B: Copper sulphate is found in the plumbing (septic tank) section of your hardware store  under the name root kill. Be sure to read the label and don't get the environmentally friendly organic crud. Chemical will be 99.9% pure tech grade or close enough for government work. Be sure to recrystalize unless you are under the employ of the Ministry of Finance or the IRS.

C: Cheaper way to produce cupric chloride - With no measuring!
Chore Boy copper brillo pads from wherever - fine mesh copper makes reaction time less forever time.
Muriatic acid (12M HCl) from hardware store - cheap as hell, gallons will last forever
Hydrogen Peroxide solution from drug store - 1.89 for half a liter? I'll take two!
Get a glass or plastic bucket, throw in your chore boy, add some acid, throw in a little peroxide, wait a bit.

Liquid in balanced solution is only H2O.
Blue liquid is cupric chloride in H2O solution
If it turns black, it's copper I chloride - add more peroxide (small amounts at a time)
Green-white precipitate is oxide of copper - you added too much peroxide - add more acid (little bit) until it goes away.
When you're done, you shouldn't have any black and a tiny amount of oxide on the bottom. This ensures when you bake the liquid you have no HCl fumes eminating from your container.

When you bake it, it's a bit touchy but impossible to jack up. I started at 300F and worked my eay down to 200F over several hours in a glass baking pan. I also made an f-tonne. Leave on the vent, and make triply sure there is no HCl left in the solution or you'll gas yourself and pit your oven. If you accidentally overbake, the anhydrous salt is copper-brown, just add water or let it sit in a humid environment and it will leech the moisture out of the air and turn back to a green-blue color. Copper I chloride is insoluable in alcohol and very slightly soluable in water, Copper II is pretty durn soluable in alcohol extermely soluable in water. Play the soluability game and purify, purify, purify!

[fledarmus]

Nice writeup, Aliphatic - I think that's worth resurrecting a post for!