Copper Chloride question

I have an odd little problem, I wanted to synthetize some copper chloride, so I used fairly pure chemicals... fine copper wire from stripped telephone wire, and concentrated technical grade HCl.

I put a ball of Cu wire in a beaker and topped off with HCl. The reaction was slow but after a week, all the copper was gone.

Now my problem is... CuCl2 and/or CuCl solutions should have a light blue to blue/green color, but my solution right now is a very dark brown color?

I looked-up various resources and no Cu salt should be brown in a solution, especially with only Cu and HCl as the ingredients?

I have no doubt as to the purity of the ingredients, and even if there were impurities, it wouldn't affect the color that much! I succesfully synthetized large quantities of CuSO4 with that same wire, and the acid produced very clean-looking solutions of Zinc Chloride, ferrous/ic chloride and Manganese chloride.

Could it be that my synthesis formed some weird copper oxychloride complex?

Oh, one last bit, when I neutralized the remaining acid from the paper filter, I poured a bit of sodium bicarbonate solution on it and the resulting foam and solution was a beautiful sky blue, which is what a chloride or a carbonate should look like.

Robert

Oxygen oxidized copper in HCl so a small amount of CuCl2 formed. CuCl2 reacts with copper to make two molecules of CuCl (Copper (i) chloride). CuCl is then oxidized by HCl and air to make CuCl2 again. And the cycle starts again until all copper is gone. In the end you have CuCl(which is brown) mixed with CuCl2. You need to bubble air through it or just stir it or leave it in the air with excess hcl to oxidize it to green CuCl2.

When I was dissolving copper and this happened (actually the solution had some brown CuCl mixed with Cu metal) I put into the solution small amount of NH4NO3 so it dissolved copper during the night. I the morning i had CuCl2 mixed with small amount of Cu(NO3)2

[Edited on 27-11-2010 by Random]

It could be also because of high concentration, check this page:




[Edited on 27-11-2010 by Random]

Success!!!

I had a feeling I needed to oxidize somehow the solution...

So I quickly pulled out a few test tubes (shattering some in the process, argh!) and put about 3 ml of my dark brown solution in two tubes. I added very gently a bit of H2O2 to the second tube and voila!! The solution became instantly a bright emerald green, as seen in the picture.

@ Random: The addition of Ammonium nitrate, (in the 1st test tube) did nothing, the solution remained murky brown, and from what resulted in test tube 2 with the peroxide, there isn't any elemental copper surpended in the solution.

Robert

Quote: Originally posted by Arthur Dent

I put a ball of Cu wire in a beaker and topped off with HCl. The reaction was slow but after a week, all the copper was gone. Now my problem is... CuCl2 and/or CuCl solutions should have a light blue to blue/green color, but my solution right now is a very dark brown color?

Nice to see that there are more people who find this nice riddle

I have devoted multiple webpages and hours and hours of experimenting to this:

http://woelen.homescience.net/science/chem/riddles/copperI+c...

Have fun reading all of this and hopefully it gives an explanation to what you observed.

Wow! Thanks Woelen!

A fascinating series of experiments, showing how Cu reagents with Cl give unusual results! I have added your site to my favorites!

I found in my selection of vintage reagents an antique bottle (Fischer ACS, circa 1950) of CuCl that unfortunately turned into a rock solid, very light green mass... Can't even scrape some off because it's so hard!

Anyway, i'll try to slowly dessicate the CuClx solution I just made, and see what color it turns into.

Robert

yeah ive seen that too. I always assumed my HCL had some Fe contaminates that where oxidising

I have allso repetadly seen zinc desolving in HCL to form a pink/purple solution while trying to make zinc chloride. what that means i dont know either

Interesting, I had the same brown solution that contained some copper metal, excess hcl and some that brown stuff. I added NH4NO3 and the copper was dissolved next morning and the solution was green like when you added h2o2. Maybe air oxidized it or small amount of nitric acid that was produced with nh4no3 in hcl. There could be also oxygen included in all this.

It's interesting though that you are researching this