# Understanding copper chloride



## Varmint (Mar 7, 2014)

First let me say I'm unable to find the copper chloride tutorial on LaserSteves site, and I've read most if not every post here with "copper chloride" in it.

So, here's the 1st question: When using Hydrochloric and Peroxide, what is the purpose of adding CopperII Chloride before using the solution to dissolve base metals? I've seen this in at least 2 videos, but in order to generate the CopperII Chloride, one of the starting methods is to use the same Hydrochloric and peroxide, feeding it pure copper! I am utterly confused on this point.

2nd question: So you've dissolved copper and other base metals to the point where the HCl/CuCl2(2)/H2O2 is saturated by evidence of a light colored CuCl precipitate. The cure for this is the addition of oxygen (air bubbling or peroxide), putting the CuCl into solution as ever increasing concentration of our CuCL2(2). Why wouldn't the proper approach be to drop some elemental copper (steel is supposed to be slow but effective, aluminum fast and exothermic)?

The two questions are essentially tied together, or at least the answer for the first helps lay the foundation for the second to some degree.

If the CopperII Chloride is doing something beneficial, I'm good with that, but if it's more of a conserving a few pennies instead of just starting over with fresh acid and peroxide, I think I'd be more inclined towards the latter.

Thanks for your time.

DAS


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## butcher (Mar 7, 2014)

Varmint, 
Recheck Steve's web site again, you just missed it, there are many discussions of this on the forum also, keep studying to get a good understanding of the process, from your questions I can tell your missing the idea of how it works, I will try to make a very short explanation here, but you will need to study more and read the document on Steve's web site...

HCl will not dissolve copper, but it will dissolve copper oxide, making a light green solution of CuCl2 copper II chloride.

The oxygen from the 3% H2O2 in the acid with copper oxidizes the copper to copper oxide which is then dissolve or oxidized again by the HCl to form the CuCl2 copper salts in solution, the HCl is reduced to chlorides in the process.

CuCl2 will oxidize copper dissolving it into solution, as the solution is saturated with copper ions the solution changes a dark brown, with both CuCl2 and CuCl in solution, as more copper is dissolved and more CuCl2 is reduced to CuCl, you will notice a white powder forming in the bottom of the solution of the dark brown solution, the white powder of insoluble copper chloride CuCl, at this point there is no free HCl, no free oxidizer (oxygen) or no free CuCl2 to dissolve more copper, but we can rejuvenate the solution with a little HCl and oxidizer (3% H2O2) or better yet at this point with air bubbled into solution (too much H2O2 can dissolve gold this is where using air is best). the Brown CuCl solution change back to a light green CuCl2 solution, Now we can put more copper into solution with this CuCl2 leach ready to oxidize copper again.

notice above CuCl2 is an oxidizer for copper (Here CuCl2 is reduced to CuCl as copper is oxidized into solution), so as long as we have a nice green solution of copper II chloride we can use it to dissolve copper...

As far as other base metals (See the reactivity series of metals) these base metals are above copper, they will cement copper from solution, Example if we used iron it would cement copper and make an iron chloride (now we no longer have a solution of copper chloride), if we had a more reactive metal or several reactive metals the metals would cement metals that are less reactive, as they go into solution we no longer have a working leach, if the metals are above Hydrogen in the reactivity series they produce hydrogen gas shoving the hydrogen out of our solution (without hydrogen our solution is no longer acidic) so in essence we can end up with an hydroxide of base metals in solution...

For the copper II chloride leach to work it is best used to leach copper only. although it will attack base metals if we choose to use it at the cost of not being able to reuse the solution (there is a bit of wiggle room here but at this point you need to get the basic understanding of the leach first.

Read all the documents on Steve's web site, you will find it there, keep studying the copper II chloride leach on the forum...

Sorry for the short explanation I have tried to explain this so many times in so many different ways, it gets boring I hope you understand.


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## Varmint (Mar 8, 2014)

Butcher:

Thank you for the detailed explanation. In essence the following sentence "clicked" it for me:

"notice above CuCl2 is an oxidizer for copper (Here CuCl2 is reduced to CuCl as copper is oxidized into solution), so as long as we have a nice green solution of copper II chloride we can use it to dissolve copper..."

I don't know what it is about Steve's site, none of the videos work for me, and from the searches I've tried I've obviously clicked the wrong thing as the results always point here (not a bad thing in itself) but I get the feeling I'm overlooking the obvious. I'll give it a few more tries, that will eventually "click" too.

I was especially shocked to find only 5 references or so in Hoke's regarding copper chloride, each of those seemed to discuss it ending up in solution as a byproduct of a reaction, not necessarily it's use as a copper etchant. 

As with many just getting started, I made a huge mistake of learning something new enough to cause excitement, in fact I'm sort of proud I came up with it on my own. I was thinking about aqua regia, and it dawned on me if I used HCL and a nitrate, I should have a shortcut to aqua regia, with "table salt" falling out. Pour off the mixed acids, and there you have a "stab" at regia, one fraught with its own problems. So, I took a few fingers from PC expansion cards either ancient technology (worthless but functional) or failed but retained because I seem to be something of a hoarder for that sort of thing.

It was amazing to watch the speed at which every trace of metal (no pun intended) disappeared into solution. Then I realized I had created a soup of much more difficult extraction, but knowing of course it was all still there, no matter how hard I made the job of separating them. So the study began in earnest, and I learned why you trim close (eliminate via's and the solder they might contain, leaving you with just copper and the gold flash, the perfect task for the copper chloride and AIR, to have the foils untouched and a solution hungry for more copper.

Anyway, it should be fun pulling it all apart. As a side note I have several 8 oz .999 "coins" my mother had set my way, one of which my son opened the case as a youngster so is now tarnished and finger printed. Since these are barely above spot value, I have the one to get started with, and will probably use inquarting as the preferred method going forward, that is once my current mess has been cleaned up. Too bad nitric is so expensive and so closely watched, now I'm having to consider distillation so I have clean nitric to work the inquarted material. I understand the traditional sulfuric/nitrate mixed acid is better (no chlorine = no regia), but still, pure always has to be better, or at least that's my current mindset.

Thank you again for your time, I'm the type that understands why we are encouraged to read Hoke first, so I'm not here to try and formulate questions so they don't appear to be the direct request for hand holding like so many are.

DAS


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## Varmint (Mar 8, 2014)

Found my way around Steve's site, but the videos still won't run for me.

A amazing amount of learning is about to commence...

DAS


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## bmgold2 (Mar 8, 2014)

Varmint said:


> Found my way around Steve's site, but the videos still won't run for me.
> 
> A amazing amount of learning is about to commence...
> 
> DAS



You probably need a plugin installed in your browser if you are using Windows. If your using another operating system, you might be out of luck. I use Linux operating system and Firefox browser and can't watch those videos. If you figure it out, let us know what worked. I'd like to see those videos and have tried all kinds of things to get them to work with this system but it looks like they only work with Windows operating systems. Don't seem to work on a mobile phone either.


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## butcher (Mar 8, 2014)

Varmint,

Hoke did not have much to mention about the copper II chloride leach (misnamed AP or acid peroxide), she was dealing with different materials in a different time in history, I have seen a couple of references of this leach being used in the mining industry, but I think where it has been most popular is in the electronic industry as a method of etching the copper on electronic circuit boards (to make the copper traces to solder components to, here the copper II chloride etching solution is a viable alternative to the ferric chloride etching solution...

The copper II chloride etch is one of the "Work Arounds" you will find on the forum, Laser Steve was the one who brought it to the forums attention as a method to use to etch copper leaving the gold, Steve having electronic experience, and a bright mind, put two and two together to bring this method to fruit, using a common known etching solution for copper that would not dissolve gold, (just a brilliant mind, seeing the obvious, to solve a problem).

Keep studying you will find many "Work Arounds" on the forum.
Hokes will give you the general principles and a working knowledge of how to deal with most anything, and is the best source I know of, especially if working with metals from the jewelry, or dentistry trade's where her focus was on, Miss Hokes approach to teaching the science, chemistry, and art of this science for us to learn to recover and refine precious metals is just such a valuable tool, no matter if you are working with materials she discusses in her book, or other materials she does not discuss, like mining or recovery and refining metals from modern day electronic scrap, She teaches the basic understanding needed to understand the principles.

I can see you have a ton of things to learn, but I also see you are very bright minded, and will be a fast learner, but I still say take some time and study, before being tempted to jump in and try things you have not spent enough time studying, your gold will still be there when your ready.

Jumping in too soon just gives you troubles, and is as easy way to lose gold or precious metals, time studying also gives you time to increase you scrap metal piles, and learn more where to find the scrap and plan a method of approach, and learn more how to work safely. and deal with the accumulation of waste that comes with working with these materials and chemicals with metals.

Welcome to the forum I think you have found a science that you will find interesting to study many years to come.


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## sharkhook (Mar 8, 2014)

Thanks for that bit of history butcher. I had been wondering how it evolved to the way it is used for recovery.


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## Palladium (Mar 8, 2014)

:arrow:


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## Geo (Mar 9, 2014)

I dont know about Ms. Hoke's book being the best but it certainly is the most cost efficient. At the low, low price of $0.00, You too can own You'r very own copy of C.M. Hoke's book "Refining Precious Metal Waste" by downloading it here from the forum. If you wanted to part with the coin (actually, a lot of coins) You can buy the various books where you can find all of the processes described by Ms. Hoke in that one book.


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## justinhcase (Mar 9, 2014)

I have read the PDF once in a while but like the real thing as I truly be leave you digest from a book better.
I have found a copy of C. M. HOKE “REFINING PRECIOUS METAL” PAY DIRT GOLD REFINING GOLD RECOVERY.
For a fair price but cant find a copy of A Handbook Refining Precious Metal Wastes for the lest than half of the first edition cost.
Where can you find a real copy that you can afford to get dirty?


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## FrugalRefiner (Mar 9, 2014)

You have a couple of options for a hard copy of Hoke's book.

First, you'll find a link in my signature line for a printer friendly copy. You can print it at home, or, as some members have done, you can take the pdf file to an office supply store like office max, staples, etc and have it printed and bound there.

If you just want to buy a hard copy, Gesswein has the best price I've seen at $54.75. Shipping is a bit pricey, but you can have a copy delivered to your door for around $70.00. Here's a link to their book page: Gesswein Book Page. Hoke's book is near the bottom of the page.

Dave


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## bmgold2 (Mar 9, 2014)

justinhcase said:


> I have read the PDF once in a while but like the real thing as I truly be leave you digest from a book better.
> I have found a copy of C. M. HOKE “REFINING PRECIOUS METAL” PAY DIRT GOLD REFINING GOLD RECOVERY.
> For a fair price but cant find a copy of A Handbook Refining Precious Metal Wastes for the lest than half of the first edition cost.
> Where can you find a real copy that you can afford to get dirty?



What I did was print out the Printer friendly version of Hoke's book and then assembled all the folded pages into a book. It's not the most professional method of book binding but I clamped the pages together between a couple strips of wood and drilled a series of holes along the edge and sewed it together with some heavy string. Then I smeared wood glue along that edge covering the string.

So far this book has held up pretty good for me. It took a while to print it all out and then a little more time to sew and glue it together but I'm happy I did it. It's much easier than just reading the PDF file on the computer and allows me to hi-light things I feel are important and write notes right in the book. The actual printing takes the longest amount of time if you don't count waiting for the glue to dry.




A bit easier option might be to just use a hole punch and put the pages in a binder. If you really want to get fancy with the book you could look up book binding on YouTube and make it into a leather or cloth bound hard cover book that really looks professional but my quick and dirty method got me what I was after, a copy of the book that I could read away from the computer.


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## justinhcase (Mar 9, 2014)

Yes that is always an option but I found the other hook book for a fiver and you cant beat the feel of a real book.
If I can work the cost into a business expense I will grab a first edition for my collection (Only Five F.E.s' but a lot of other odds and ends)
If they are £120 now you just know they will be worth a hole lot more to any one who comes latter.
Hook worked out how to make gold from wood pulp not just refine it.


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## bmgold2 (Mar 9, 2014)

justinhcase said:


> Yes that is always an option but I found the other hook book for a fiver and you cant beat the feel of a real book.
> If I can work the cost into a business expense I will grab a first edition for my collection (Only Five F.E.s' but a lot of other odds and ends)
> If they are £120 now you just know they will be worth a hole lot more to any one who comes latter.
> Hook worked out how to make gold from wood pulp not just refine it.



Collectors will pay a lot for an original but many (if not most) of the people here will settle for just having the information it contains. I'm thankful that it has been made available here for free. Even if you had a first edition of that book, you'd still likely want a "working copy" that you are not afraid to "play with". Collecting old coins is also a great hobby but running your fingers through a pocket full of change is still fun and avoids the guilt that you might scratch them.


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## FrugalRefiner (Mar 9, 2014)

justinhcase said:


> Where can you find a real copy that you can afford to get dirty?





> If they are £120 now you just know they will be worth a hole lot more to any one who comes latter.
> Hook worked out how to make gold from wood pulp not just refine it.


Your last two posts seem to be in conflict. If you buy a copy of the first edition for £120, I would hope you wouldn't ruin its value by getting it dirty.

I bought a copy of the reprint as a reference when I created the printer friendly version so I could correct a lot of errors. I used it solely for that purpose. It now sits on my shelf along with some other volumes I've picked up. I printed out a copy of the printer friendly pdf for my working copy.

Her name is Hoke.

Dave


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## justinhcase (Mar 9, 2014)

no conflict I I would always keep nice things safe but buy redundant copy's of things I like so i can enjoy them as well.
I have four copy's of Pipillon and keep the first two I wore out until they fell apart even though they are no longer of use (sorry for getting off subject please carry on)


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## goldsilverpro (Mar 9, 2014)

The best article I've seen on the subject is also on Steve's site, I think. Here's a pdf of it.

Here's the equation for dissolving copper using copper(II) chloride, CuCl2. No copper oxide is formed. The CuCl2 is what actually dissolves the copper.
CuCl2 + Cu = 2CuCl

The undesirable copper(I) CuCl is produced, which is soluble in HCl. It doesn't take much to severely affect the dissolving rate of the copper. It is easily converted to CuCl2 by continually bubbling air through the solution.

2HCl + 2CuCl + O = 2CuCl2 + H20

Were I to ever see a need for the "AP" method, I would not use peroxide at all. I would make up a CuCl2 starting solution using clean copper (wire would work well), HCl, and air. I would use that solution and air to dissolve the copper in pins, fingers, or whatever.

The article gives all sorts of information on how to do this, along with the desirable concentrations of the chemicals. It also has a simple color method for determining the [CuCl].


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## Varmint (Mar 9, 2014)

Thanks to all who contributed, I'm in study mode so I'll be back..

DAS


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## Varmint (Mar 28, 2014)

My mission to understand CopperII Chloride seems to have gone pretty well.

Note: Water used below indicates distilled water in all cases. While tap water might not hurt some reactions or processes, I'm the type to never put myself in the position of wondering if an odd result is due to contamination.

As a starting point I used the preparation instructions from the excellent PDF goldsilverpro linked to on Steve's site. Thanks to you Both.

So I took the peroxide path to getting started, quality HCl, 3% H2O2, and some pure copper. The intent was to build the base stock, something I could store in a somewhat depleted state (low on HCl), to be brought up to operating capacity by the addition of HCl and air when needed. Note I didn't mention H2O2 in the base stock. I get worried when I hear "will dissolve gold too if there is too much peroxide". Ergo, I will have none in the final stock solution...

Please refer to the CopperII Chloride Wiki: http://en.wikipedia.org/wiki/Copper(II)_chloride
Of particular interest are the (3) test tubes, indicating the color based on the concentration of Cl-.

So, I kept feeding copper to the original solution until I stated seeing the white-ish precipitate of Cupric Chloride, and just for "fun", added a bit of HCl to bring the precipitate back into solution. As many of you know, the bulk solution at this point might as well have been jet black, even the drop test was ridiculously dark. 

Next I decided to add some H2O2 to see it's effect on the by now VERY dark green liquor. Amazing to watch the color swing back towards lighter shades as the peroxide swirled in, only to 'snap" back to dark green as the mixing progressed(though a touch lighter). Finally a breakpoint was reached where the last few drops of peroxide (total volume at this point ~600ml) switched (literally, as if a switch had been flipped) to a gorgeous emerald green of fantastic clarity.

So, I learned more HCl will allow more copper ions before precipitation commences, and more oxygen (and the included water in the H202) further increases the system capacity.

Remember I said I wanted no H202 in the final stock solution? My answer to this was patience, I would use my aquarium CO2 fritted disc diffuser to inject compressed air (shop sized compressor with dryer/filter/regulator at the lab station) in heavy volume until the air had eliminated the peroxide and HCl to an unknown (unquantified) degree. This result was spectacular! 

I left the diffuser running overnight at about 6PSI, a very heavy volume of exceedingly fine bubbles. The next day the once Emerald green solution was now a similarly gorgeous Aquamarine, tending towards blue. (Should have snaped a pic!)

So, this is where the Wiki reference above comes into play. Recall the low Cl- concentration tended towards the blue? Well, this seemed to fit, and I was really quite happy with the progress, and what I thought was understanding...

Previously I mentioned a shelf-stable stock solution ready for use by adding HCl and air. Well, I decided no sense having a large volume, why not evaporate a good portion and leave a much smaller volume to store?

So I set the 1l beaker on the sand bath, dropped in a stir bar, and cranked the heat up. I set the stir speed to create a sizeable cone vortex hoping to increase the surface area, expecting the agitation to help with evaporation and allow for greater het input as well.

That worked well, but I wasn't ready for this part: As the heat increased, my Aquamarine solution slowly reverted back to its Emerald origins. It seemed to want to hang onto the Aqua hue for a bit, then the march towards green seemed to follow an anti-log curve (O2 leaving solution?) As more water (and HCl and residual H202) left the liquor, the darker it got, finally ending up quite dark (in bulk), but only 0.5g/l or less according to the PDF drop test. 

So, at this point I achieved my goal, I have a stock solution that works (quite hungry for copper with HCl and air rejuvantion), but I'd like to understand the striking change to the aquamarine, and the comparatively sudden switch back to Emerald upon appliation of heat and agitation.

Comments and hypothesis welcome. Next batch, I'll repeat the steps faithfully and get some pictures...

DAS


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## pgms4me (Mar 29, 2014)

I stand to be corrected if I am wrong,but any heat drives the oxygen out of the solution,bringing it back to where it was when you started. The warmer the solution the less oxygen it can hold.


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## Varmint (Mar 30, 2014)

pgms4me:

Yes, the heat absolutely drives the O2 out, that part is understood, but I had made the assumption (hate that word  ), that it had also driven out the HCl which might have contributed to the gorgeous color change.

The bad part of my thinking (I assume) is the color comparison was indicating the level of acid, when it really appears to be indicating the quantity of Cl- ions bound up in the CuCl2?

I guess my expectation was the color I had was what I could expect when I reduced the H2O content and (presumably) started to get crystals of the Dihydrate also shown at the same wiki page.

So, my plans are to understand the chemistry. Yes, I tend to get hung up on stuff like this, I'm doing this to learn (no expectations of vast income from my effort) and I'm not the type to explain to someone how I got my gold button; "well, I used this compound I know nothing about to remove base metals, copper in this case, leaving the gold substantially pure enough for easy further refinement". I want to know why H2O2 or air work well, difference being you can add too much H2O2, but not air. That sort of open-ended "rule" drives me to learn "what IS too much H2O2", and If I have enough O2 concentration through air injection to cause the gorgeous color change, why is THAT not too much?

Further, if my O2 saturation wasn't too high, does that mean I can add H2O2 until I get the same color shift, or do the two differ enough in practice that the amount of H2O2 to cause the same shift is way too much and gold will go into solution?

Its all about learning and understanding. There are probably thousands of people who couldn't care less about how it works, but could be wildly successful scrapping/refining for profit. I want to be the guy that knows the actual chemistry, and again, have no dreams of being a wildly successful PM processor. 

DAS


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## butcher (Mar 30, 2014)

Interest and curiosity, seeking the answers to your questions, working to figure out those things you have questions about, and doing tests to see what happens, what a great way to learn this science.

Keep up the good work, keep us posted.


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## Geo (Mar 30, 2014)

Oxygen does drive the reaction forward but heat will also drive the reaction as it does when using AR. Due to evaporation, you have to replace the hcl. Using air is more economical.


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## Varmint (Mar 31, 2014)

OK, some more research and experimentation.

CuCl2 is an efficient catalyst for the decomposition of H2O2, releasing of course water and O2. Trouble is, the decomp is relatively speedy and complete, most of the O2 escaping at the surface to the air. 

This means 2 things, H202 is an expensive and inferior method of providing oxygen to the solution, and it's impact on the dissolution of gold foils is limited to a brief timeframe.

For testing I began with (2) 50ml beakers filled to ~30ml with the same prepared CuCl2 solution described earlier. To each I added 1gr (64mg) of copper to give the solutions a load to digest.

In the first (non-peroxide) breaker I added 10ml of distilled H20 to approximate the water-only content of the 10ml of the 3% H202 I added to the second beaker.

The first beaker was aerated by means of a short section of Teflon "aquarium bubble stone" until the color seemed to stabilize at the gorgeous aquamarine-blue described earlier. since this took an hour or so, I rechecked the volume and topped off the missing 1ml or so, then returned to aeration.

In the second beaker, H202 was added in both "large" (1-2ml or so) additions as well as drop-wise to complete the 10ml addition. No stirring or agitation was used. On the large additions, portions of the column turned obviously lighter than the non-peroxide control, but soon settled to a lighter but still more Emerald color. O2 (presumed) was seen escaping the surface. By the end of the additions, aside from the localized color swings, the two solutions ended up at very nearly (extremely close) aquamarine-blue color. If I were to call one "darker", it would be the peroxide example.

It was assumed at this point the H2O2 had been fully catalytically decomposed, so the next step was to place both side by side in a water bath on the hotplate. As before, as the temperature increased, the solutions began to revert to the Emerald coloration. The intent of course was to see if any H2O2 had "survived" decomposition, in which case example 2 would return more slowly to the "base" Emerald. Instead, they changed in essential lock-step. By the time the first cavitation bubbles appeared, both were nearly the base color, a second or two of boiling of the bath water insured they were as Emerald as they were going to get.

It was then I noticed the peroxide example retained is ever-so-slight darker color. My assumption is I was either too generous in my water-content equivalent addition to example 1, or I topped off slightly too generously following the bubble up to O2 saturation.

So, my conclusion is, peroxide is a complete waste of money unless you use it solely for the short reaction time when generating your mother liquor etchant as described in the linked CuCl2 PDF above.

DAS


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