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jeneje

jeneje

Well-known member
Joined
Jan 23, 2011
Messages
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Location
Knoxville Tennessee
After AP is saturated with copper chloride II do I need to replace the AP with new solution to continue with dissolving the pins. I added air to aerate the solution but it has completely stopped at this point.
Thanks
Ken
 
If it's completely stopped you have to expand the solution. Or if you don't have room in your container to expand it, you have to remove some of the AP solution and then expand it. But if you add more HCl and/or Hydrogen Peroxide, you are going to run the risk of dissolving some of your Au into solution. It will cement out as Cu II is created, but it's easier if you don't.

Scott
 
if you either remove the material or move the solution to another container and bubble air through the solution, the extra copper will drop out of solution as copper chloride crystals. AP solution is saturated when the solution turns brown. if its still green and the action stops, it more than likely means it is saturated with another base metal like zinc or tin or lead. in that case, do the same as afore mentioned except do not bubble air through the solution, but just let it sit undisturbed and the tin,zinc,lead will oxidize and drop out as their salts as a white precipitate.
 
In using AP to dissolve base metals, two important things are easily forgotten:

1.) The driving reaction in AP is the following:
Cu2+ + Cu(metal) + 4 Cl- <==> 2 [CuCl2]-.
Other base metals than copper can also be oxidized, provided, they are more easily oxidized than copper.

2.) Reoxidation/regeneration of [CuCl2]- to Cu2+ with oxygen from the air consumes acid, thus necessitating to add acid (as HCl) from time to time when using an air bubbler:
4 [CuCl2]- + O2 + 4 H+ ==> 4 Cu2+ + 2 H2O + 8 Cl-.
Water has also to be added from time to time, in order to keep all the metal-salts formed in solution.
 
I did some pins the other day that was about 50 % zinc and 50% copper in ap. I noticed first the zinc went into solution and it turned brown. After 2 more days the copper went into solution and it turned green with white powder at the bottom, zinc i'm figuring. Can zinc also act as ap by being regenerated to etch more? Then also how did the copper wind up in solution and the zinc as a salt? I figured the zinc would cement the copper out of solution and not the other way around.
 
If i understand here, the oxygen i added by aeration to the AP will consume the HCL out of the AP, makes sense! How would one tell when to add more HCL to the solution? When adding H2O to the AP what would be an appropiate amount?

My understanding was that the addition of HCL with aeration would regenerate the AP causing it to digest more of the base metals. So adding H20 will keep the salts in solution. I am not sure here if AP creates mastannic acid or not i have never done a complete digestion with AP.
Thanks for your information here freechemist,
Ken
 
When you add air, O2, to the ap what happens is the O2 oxidizes the copper so that the hcl can dissolve it. Hcl alone will not dissolve copper, but it will dissolve copper oxide which is what the air is doing. When you have white copper chloride crystals on the bottom the hcl is expended and more needs to be added. You actually don't even have to add H2O2 to it. All you need is air and hcl. The H2O2 just helps jump start the reaction to get some copper into solution so it can start etching. You can even just use the white copper chloride crystals, add hcl, and air and it will do the same thing.
 
the zinc and tin oxidizes into zinc oxide and tin oxide. both are white crystals. copper also oxidizes in this solution but with one big difference, the copper oxide is dissolved by the hcl and converted to copper chloride. if you test the PH of your solution, it will let you know when to add more acid. the solution has to dissolve a lot of copper to consume the amount of acid generally used. ive had AP that ive re-used for months that is very acidic. dont forget lead. older electronics will contain lead that dissolves in AP. it too will oxidize and precipitate out as long needle like crystals.
 
Thanks guys that answers alot of questions i had. I wanted to try the AP instead of Nitric to dissolve the base metals, just seems to be safer.
Ken
 
I did such an experiment some months ago.
I replaced the AP solution several times. Why?
Each time the AP solution gets saturated by another metal, climbing the reactivity chart up until there was silberchlorid created.
To my understanding AP only works for one base metal at a time. So if your AP is saturated with zincchlorid, no more copper will be dissolved.
Assuming that, I dont understand the statements made, that lead,zinc,iron and other BMs will simply drop out.
As they drop out, they should behave like a precipitant.
They dissolve and precipitate over and over again. That is why the reactions seems to stop.
And that is why I completely changed the AP each time the reaction slowed down.
Each AP step will create a different salt and have a different color. But at the end of the day, you can all pure it into the wasted AP bucket and BMs will precipitate, Cu(II)Cl will remain since it has the largest part of the materialmix.
Correct me if I am wrong, but AP can only hold one metal at a time.(unless you dont add endless amounts of HCl, then there is "room for everybody")
At the end I cam to the conclusion that AP and pins is not a good process. I will try the cell for that and expect a better result from that.
 
Marcel said:
I did such an experiment some months ago.
I replaced the AP solution several times. Why?
Each time the AP solution gets saturated by another metal, climbing the reactivity chart up until there was silberchlorid created.
To my understanding AP only works for one base metal at a time. So if your AP is saturated with zincchlorid, no more copper will be dissolved.
Assuming that, I dont understand the statements made, that lead,zinc,iron and other BMs will simply drop out.
As they drop out, they should behave like a precipitant.
They dissolve and precipitate over and over again. That is why the reactions seems to stop.
And that is why I completely changed the AP each time the reaction slowed down.
Each AP step will create a different salt and have a different color. But at the end of the day, you can all pure it into the wasted AP bucket and BMs will precipitate, Cu(II)Cl will remain since it has the largest part of the materialmix.
Correct me if I am wrong, but AP can only hold one metal at a time.(unless you dont add endless amounts of HCl, then there is "room for everybody")
At the end I cam to the conclusion that AP and pins is not a good process. I will try the cell for that and expect a better result from that.
Click to expand...

Marcel, oxides behave differently than elemental metals. the process of dissolving metals with acid is due to ionic exchange. once certain metals oxidize, it takes on different characteristics from the original metal. tin and zinc oxidizes in the presence of hcl to make a form of salt that will not dissolve in hcl alone. much like tin oxidizes in the presence of nitric acid to form the hydrated form of tin oxide (metastannic acid) which will not dissolve in strong acid. copper also forms a salt that will not dissolve in hcl until its heated. i cant remember the chemical formula for it right off the top of my head (im far from a chemist :lol: ) but there is certain things you pick up along the way.
 

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