# i finally figured out why i use to much nitric



## steyr223 (Nov 11, 2013)

Hi everyone 
I am curios if anyone else had experienced this

I set out to do a handfull of boards that almost looked like memory fingers once cut



I figured minimal bsse metals so covered in hcl and added potassium nitre untill all gold in solution 
Problem..gold never seems to go into solution after waiting days and visibly there's no more basemetals i still see gold foil/flakes. :shock: 

I gues this is where my color blindness comes in 
I believe the color of the solution (dark green to brown) and the little specks of board and mask are very reflective and appears like gold
The way i figured this out was by adding 100ml of bleach while the solution was still warm and all the so called gold was still there. 

This i have enough experienceto know was then not gold but again i am left with to much nitric :lol: 

I think this time i will try cementing instead of the tedious evape


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## steyr223 (Nov 11, 2013)

Sorry in the previous post picture the bottom right piece has a thin line of gold across it, this is what i was referring to.

Thanks steyr223 rob
Any comments or criticism are welcome.


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## Pantherlikher (Nov 11, 2013)

Hi.
I have done some boards similar from monitors, scanners and printers. not many but enough to see if it would work.
2 days in HCL to remove solder and anything else. Rinse and then into AP for a couple few days. Most flaked off but there is always small specks at mask that wont scrub off. Board goes into HCL + bleach for a short time and gold dissolves fine. 

You are going right to poor mans AR right? Seems a bit more expensive using more then neccessary acids. There is at least copper, nickel and maybe some solder. Do you depopulate and soak in HCL and rinse before AR? 

I can see that the mask can reflect like gold flakes. Maybe next time you can remove any material at this point. Solution should be positive for gold. Then you can add some more AR to material and test to see if gold is there or not the 2nd time. This would help prevent too much nitric in your gold solution.

Just my 2 cents I found laying around.

B.S.


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## steyr223 (Nov 12, 2013)

Thanks pantherlikher
I just wanted to do something different
Not really trying just experimenting
When i do the poor mans AR the proper way it cuts my time down to less than a day fron start to melt

Its not that im in a hurry but i can only fit so much stuff on my truck and when the words. "theres to much stuff" exit my mouth ...lets just say it's a real bad day :evil: 

Yes i soaked in hcl (did rinse and rub before CuCl2) wait!
Sorry that was the last ones

These i close cut just the gold out no solder or parts left
And yes i tested with stannous but why when with nitric shows nothing
And the few times it did show it still doesn't mean all your gold is im solution 
Anyways thanks steyr223rob


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## JHS (Nov 12, 2013)

Rob,
Maby you could put just a small button of gold in
your ar. that would help you see when gold is in solution,assuming the button is thicker than what 
you are processing.might help with the color blind thing.
just a thought.
john


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## steyr223 (Nov 12, 2013)

Thanks john
actually I put a small bb in this time (1gm) i just put it in at the wrong time

I poured out my solution to see if the material still had gold on it ,my thought was if I poured out the solution why not pour it into an ice bath ,rinse material well ,add a little sulfumic acid(just in case),let settle, filter with Charmin plug

So I did all this and then I decided to put the bb in

am i right to believe that is too diluted of a solution to even think about eating the bb

Thanks steyr223 rob


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## JHS (Nov 12, 2013)

I think I would just let it sit a day or two
and see what it does.even weak acid will
eat at the bb.
john


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## g_axelsson (Nov 12, 2013)

steyr223 said:


> I figured minimal base metals so covered in HCl and added potassium nitrate until all gold in solution
> Problem..gold never seems to go into solution after waiting days and visibly there's no more base metals i still see gold foil/flakes. :shock:


Your first mistake, there is a lot of base metals. The gold plate is thin compared to the copper foil. By dissolving everything in AR you made a mess of mostly base metals and just a bit of gold in solution. I suspect that your cards was only flash plated and that is even less gold when compared to the copper foil.

What you were seeing floating around, I have no idea.

I would treat it as the standard newbie mess and cement it on copper and restart.

Göran


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## steyr223 (Nov 12, 2013)

Thanks john
Thats exactly what i am doing

Goran :? Standard newbie mistake :shock: 

I have done this process with porcelain cpus,porcelain ic's,pc card close cut fingers,memory close cut fingers and had success probaly 20 out of 30 times with no problem getting the base metals out.
The other 10 or so times i still got my gold it just took longer
Maybe you should go precipitate some tin :mrgreen: 
The above tin statement was in fun and no way a dig or a stick or cut or burn
Whatever all that means :lol: 


For anyone new reading this do not attempt as it is a process that should be left to the pros it is much more difficult than a/p and then Hcl/bleach

Plus this method let's me practice harolds washes

What can i say ,when your doing 5 or 6
Processes a week (.7-1,2gm at a time)
CuCl gets boring 

Anyways thanks for the input 
Steyr223. Rob


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## g_axelsson (Nov 12, 2013)

Rob,

maybe you have some trick to drop gold from really dirty solutions, then good for you!
Personally I prefer to drop gold from as clean solutions as possible, it gives me less problems.
But I don't think you can say that there is "minimal base metals" when it is gold plate on top of copper traces. I would not recommend your method to any newbie as it would be easy to get into problem. The basic rule is to remove as much of the base metals before dissolving the gold.

At least that is my point of view on it.... walks away to look at my collection of dropped tin... :mrgreen: 

Göran


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## Harold_V (Nov 13, 2013)

My opinion?
I don't share the opinion with others that it is difficult to precipitate from dirty solutions. I don't recall EVER having a problem with getting the gold to come down, but I do recall how dirty it was after precipitation, due, generally, to a huge amount of drag-down of impurities, some of which were difficult to remove unless the gold was processed a second time. In fact, a great deal of the gold I precipitated came from very dirty solutions, as my preferred method of processing filings from the jeweler's bench was to incinerate, screen, give them a wash in hot nitric, then to dissolve directly in AR. The resulting solution was ALWAYS extremely dirty, but that was the gold I'd use for evaporation (after melting to buttons), so it, in effect, got processed three times. 

The real problem associated with dissolving base metals along with gold is when base metal remains, and gold is cemented. If you can get around that problem, and intend to refine the gold a second time, to improve quality, direct AR processing can be to advantage in a few cases, but, in general, it's a fool who dissolves base metals along with his values. So then, in my opinion, working with dirty solutions shouldn't present any particular problems, although, in evaporation, they can. 

Harold


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## steyr223 (Nov 13, 2013)

Goran i do agree it is much easier to get all the garbage out first ,but lately even that doesn't seem to help

I always get my gold but as i said in one of my previous posts no more text book reaction . 

I believe part of my problems have to do with extremely small processes and of course very low quality material.

Harold hi how are you and hows the wife

When you say evaporation do you mean the gold you put back in to consume any free nitric

Thank steyr223 rob


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## g_axelsson (Nov 13, 2013)

Dirty solution in this case is probably 0.3 um gold flash on 18 or 35 um copper, ie 3-1% Au and 97-99% Cu. The few times I have tried to precipitate gold from a solution with a majority of base metals I have gotten a very fine black powder that almost never settles.
Most of my batches have been 0.5-3 g of gold.

But I haven't recovered more than 55g gold so far so my experience is nothing compared to Harold. 8) 

Göran


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## butcher (Nov 13, 2013)

I think what Harold calls a dirty solution, and what some of us with this low gold content electronic junk call a dirty solution, is possibly two different solutions.


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## g_axelsson (Nov 13, 2013)

Exactly, that's why I wrote out the math that I knew instinctively in my mind. Last time I ordered circuit boards 18 um copper was the thinnest option but 35 um standard. Gold flash is close to 0.3 um.
Harold didn't go directly to AR, he pretreated the filings with nitric so in theory anything golden should be at least 25% gold. Granted, there could also be other metals as stainless that is dissolved in AR but not in nitric alone.

Göran


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## steyr223 (Nov 13, 2013)

Answer me this then if fingers
Can be done this way and there supposed to be 30 um(not sure if um is micron u is micro in electronics )
And copper is 18-30 um that means 
50% + gold 
Is this what you condider minimal base metals

Thanks steyr223 rob


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## g_axelsson (Nov 13, 2013)

No, um is micrometer. (Should be the Greek letter micro actually, but it's so hard to spell μ if you don't have the correct keyboard. :mrgreen: )

Plating is never 30 micrometer, it is closer to 1 micrometer, it could be 30 micro inches (which is equal to 0.75 micrometer)

Personally I would never do fingers in direct AR, I always separate the gold from the circuit boards first before going to AR by dissolving the copper only.

What I would consider minimal base metal is basically carat gold or similar, for example incinerated BGA tops.

Göran


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## steyr223 (Nov 13, 2013)

Ok now i understand the math much better i was thinking 30 microns was
Micro meters( hey how come we dont have micro feet and what ever happened to deca :lol 

I tested my solution positive for au 8) 
So i droped with smb and probaly 1/5th
Water to volume of solution(it was already diluted)
This is the strange part 
the .2gm or so was at the bottom before i finished adding the smb/h2o mix and the powders looked like someone broke a mechanical pencil led into pieces
About 1/8th inch long

Also the solution is still just as green as it was before
Thanks steyr223 rob


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## Harold_V (Nov 14, 2013)

steyr223 said:


> Harold hi how are you and hows the wife


Doing well for an old guy, and Susan seems to be hanging in there, still putting up with me. :lol: Thanks for asking!



> When you say evaporation do you mean the gold you put back in to consume any free nitric


Yes! I should have been a little more descriptive.
When one processes filings, you simply can't use the right amount of nitric, for the only way you can know all of the gold is dissolved is if there is no further reaction. I used to determine that by adding a small amount of nitric and HCl to the given lot, once I assumed that I had all of the values in solution. That was to ensure that I did not cheat my customers. I then used the gold button(s) I mentioned to eliminate the free nitric. 

Because I precipitated from heavily concentrated solutions, I always evaporated, if for no other reason, to eliminate volume, so, for my operation, the once refined and questionable quality gold was used to great advantage. 

Harold


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## steyr223 (Nov 14, 2013)

Thank you for the clarification harold
That is what i thought
I to enjoy the benefits of the evape nugget(or in my case bb), in fact i look forward to it as it always gets bigger and refined at least 2-6 times (only cause i sold it after the 6 use 8) )

I am glad to see you back Harold i enjoy your posts very much and learn a great deal from you. Thanks

Thanks to eveeyone in fact
Steyr223 rob
Ps goran did u say 55 gms ?
Really !! your posts are so informative 
They speak in pounds :mrgreen:


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