CHRIS25 - 18-3-2014 at 06:54
Purifying copper. The only thing that I can find no information about is the approximate Molar strength that the electrolyte must be. Would a 1 mole
Copper sulphate solution suffice for most purposes, can it be too concentrated?
Thankyou.
macckone - 18-3-2014 at 07:40
For a sulphate plating solution the key parameters are pH and current density. 1M solution will work, in fact you may want slightly more dilute.
And there are other additives that should be in the solution.
You will need to add copper carbonate as the plating progresses to
balance the pH.
Try the following two books:
http://books.google.com/books?id=DJIoAQAAMAAJ&dq=plating...
and
http://books.google.com/books?id=YxkNAAAAYAAJ&dq=plating...
They are older but have much valuable information.
CHRIS25 - 18-3-2014 at 08:13
Hi, Thanks for the book references but I will give those a miss. I simply want to purify some copper now and again. However you mentioned PH, most
of the references I read point to an acidic copper sulphate, but say nothing more.
macckone - 18-3-2014 at 08:47
Ok, I will spoon feed you 
Dilute your 1M to .75M (probably doesn't matter much).
chloride needs to be 30-40 ppm
thiourea needs to be 1-3 ppm (other additives are also used)
Current 200-300Amps/sq meter
references:
http://doccopper.tripod.com/copper/er.html
http://www.pfonline.com/articles/choosing-and-troubleshootin...
try a pH between 1 and 3.
Too low and it corrodes faster than it deposits.
Too high and you get oxides.
You adjust the bath down with sulfuric acid and
up with copper carbonate.
If you are using a pair of copper electrodes then
the pH should not need to be adjusted much.
If you are trying to refine copper sulfate you are
going to need to add copper carbonate regularly
to keep your pH from dropping too low.
CHRIS25 - 18-3-2014 at 10:53
Well thankyou for the spoon. I am using copper cathode and anode and copper sulphate. the rest is understood, and thanks for the explanation about
why acid and carbonate is used. But the chloride? Inhibits dendrites - understood. And the references, would not have found those, thanks again.
[Edited on 18-3-2014 by CHRIS25]