# gold coper silver alloy problem



## chemistrycoach (Dec 21, 2013)

Hello wonderful forumers ! Please extend me help 
I had a bead that compose of approx.70 percent copper and 15% silver and 5% gold
How can i seperate the gold ?

If i piut the bead in 50/50 nitric acid the copper will dissolve
But will the silver dissolve too? Wont it be push out by the copper ions in the nitrate solution ?
Because of the electromotive series copper will push out/ cement the silver because they are in the same solution with 
The copper, is there a way that copper and silver will be dissolve andleft the 5% gold
In the solution? .. i mean i only wanted the gold... kindly advise me what to do....
Thank you to all and advance merry christmas !


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## nickvc (Dec 21, 2013)

If you heat the solution of nitric and use carefully you will remove both the copper and silver just leaving gold at around 90-95% pure if done well.


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## FrugalRefiner (Dec 21, 2013)

chemistrycoach said:


> Hello wonderful forumers ! Please extend me help
> I had a bead that compose of approx.70 percent copper and 15% silver and 5% gold
> How can i seperate the gold ?
> 
> ...


There is so much to learn, and you obviously have a start in understanding that nitric will dissolve both copper and silver and that copper will cement silver out of solution. In this case, the answer to your question depends on how much nitric acid you use. If you use just enough acid to dissolve the copper - no more - you would find that any silver that was dissolved at the beginning of the reaction might indeed be cemented out as you reached the end of the reaction. But if you use enough acid to dissolve both the copper and silver, they will both go into solution together.

Keep studying and all of the bits of information will begin to coalesce.

Dave


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## butcher (Dec 21, 2013)

chemistrycoach,

Your material is low enough percentage of gold that will work.

You will dissolve both copper and silver (and other base metals) into the dilute nitric acid solution.

The nitric acid solution can hold both copper, silver, and other base metal nitrate ions in solution.

I can have a solution that has copper Cations, and silver Cations, floating around in a solution nitrate Anions. Here they are happy to stay in solution together, one will not easily push the other out of solution, one will not oxidize, or reduce the other, neither is an oxidizing agent or a reducing agent for the other, neither have free electrons to share, or have any place to take electrons from (in this solution), nothing is forcing them out of solution.

I can actually have a solution, a very complex mix of ions both anions and Cations, a dirty mix of many metal Cations and several anions in solution at once.

Take a mess (an complicated ionic soup) where we used aqua regia to dissolve a dirty batch of electronic scrap for example, where we are using two different acids, and can have many different metals, and also organic materials, we can dissolve most all of the metals into solution as Cations, we can have both nitrate and chloride Anions in solution, along with organic complexes, all happy to stay in the solution as a dirty mix, gold being at the bottom of the reactivity series will not easily be pushed out of this solution by the other metals in solution, in fact in can be difficult, if not almost impossible to get the gold back out of this solution (depending on the state of this mess).

Now say I have dissolved silver and copper into solution with nitric acid, and this was all that was in solution copper and silver nitrate, the solution would be colored blue because of the copper ions, silver nitrate is colorless, if I have strong free nitric in solution the NOx may color it kind of green.

I can add a clean copper metal bar and put it into this solution, the copper metal has a full shell of electrons in its atoms in the bar of metal. The silver ions are missing electrons, and share their electron shell with the nitrate ions, the silver would rather have its own electrons, the copper metal atoms will give electrons to the more noble metal, the silver gaining these electrons is reduced (reduction gain of electron), the copper is oxidized (oxidize loss of electron), silver now with a full shell of electrons in its atom joins together with the other silver atoms until the cluster of atoms grows big enough for us to see, these clusters of silver metal atoms keep growing in size, as this reaction is dependent of the silver ion being in close contact with the copper metal to exchange these electrons, the silver can begin to plate to the copper bar, or the cluster of newly reduced silver atoms may stick to the copper bar in clusters as the silver cements out of solution, and copper ions go into solution replacing the silver.

Eventually we will be left with a solution of copper nitrate (if there were metals above copper in the reactivity series of metals in this original solution they will still be there too), the silver being replaced by copper.

We cemented silver out of solution with copper metal (not copper ions), the silver is now a metal, and the copper metal used becomes ions dissolved in solution, the silver ions are replaced in solution with copper ions, copper metal lost electrons, silver ions gained electrons, copper gave up its electrons to silver as noted by the reactivity chart, in an electron exchange reaction, or displacement reaction...

This is kind of hard for me to explain in a post, it is really not too complicated, but can be complicated for me explain.


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## glondor (Dec 21, 2013)

Butcher, have you been sneaking out at night and getting degrees in chemistry and metallurgy ?  8) 

I understood what you wrote, so no worries about not getting your lesson across.


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## butcher (Dec 21, 2013)

Actually I have been trying to study how to move a post, from one topic, to another topic with the same name, Boy double posting has caused me to spend a lot of my time studying, Time I wished I could have used to study gold or chemistry with.

Please no double posting.
I am not that good at this, I could mess it up, no telling where your posts may go.


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## chemistrycoach (Dec 21, 2013)

Thank you so much guy's, i will be using a strong nitric acid solution to dissolve the silver and copper togetjer ( boiling )
And try to leave the gold behind to be filtered afterwards
Sorry for the double posting butcher it was done unintentinaly. Thank you


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## butcher (Dec 21, 2013)

chemistrycoach,
I needed to learn how to merge the post so no sweat this time.

You will want to dilute your 70% nitric with equal volumes or more of water, and use heat towards the end of the reaction, I would not boil it, but get it just below boiling, the dilute nitric will actually work better, the nitric will not gas off its active ingredients so bad, leaving these gases to do more work in solution dissolving metal, which would also waste less of your acid.

A little H2O2 added can also help to convert the gases that will try to escape back into nitric again lowering the volume of NOx gas leaving the system, keeping them in solution to dissolve more silver and copper.

Strong concentrated nitric acid can be such a strong solution that it can oxidize and temporarily passivate the silver, at the same time a lot of your acid is decomposed leaving the solution as a large brown cloud of NOx.

There are several situations where a dilute acid works much better, or where the dilute acid will attack a metal and the concentrated metal will not because the concentrated acid can just passivate the metal building an oxide coating.
Iron in concentrated sulfuric acid, or concentrated HNO3 in stainless steel...

I would not filter the gold which will most likely be a fine black or brown powder, let the gold settle well overnight, decant the liquid copper and silver nitrate solution, filter the solution, before cementing silver out with a thick clean copper buss bar.

I am not sure how big this "bead" you have, but if it was not very large, I do not think I would try this until I had more material, I would probably just save it to use to in-quarter gold with later.
Tiny amounts of metals are harder to deal with, and harder to not lose value in the solution or process, many small processes can mean many more small losses, these can add up over time to mean big loss of value. 

I had to study lose, loose, lost, losses just to try to explain this, I hope I did not lose you in the discussion, and I hope I used the word right in the right place, now I lost my train of thought.

I hope I have taught you as much today as you have taught me.


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## chemistrycoach (Jan 3, 2014)

Thank you very much Butcher. I really appreciated your comment.
By the way i want to ask this question to our forumers are there any other metal
That reacts as violet or purple or dark purple in stannous testing beside gold ?


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## butcher (Jan 3, 2014)

I do not know of any metal that will react with stannous chloride SnCl2 to change to a violet (purple) color like gold does.

Stannous chloride SnCl2 does react with other metals and can give color indications of these metals. 
Gold gives a violet (or deep violet that looks black dilution can show violet).
Platinum gives dark yellow to orange.
Palladium gives a green - blue.
Silver can form the white AgCl (but we normally do not test solution with silver using SnCl2).
Too much copper in solution and too much SMB, the SnCl2 test can give a brown reaction (many call a false positive for gold).

Metals like iron, copper, zinc, nickel, cadmium and others tat may be in solution do not normally react to give colors in our tests with stannous chloride.

Iron will react with stannous chloride and if too much iron is in solution, the test for gold the violet color may be slow to develop and you may have to add more SnCl2 than you normally would.

Organics can also give problems with the test.

Nitric acid left in solution can keep the metals oxidized so the colors may appear and disappear, or may not appear at all until the nitric is removed from solution.

There are metals that will make a violet color in solution (I am not talking about testing with SnCl2 here).
Metals in nitric solution as nitrates, and some of their colors,
Cobalt, rose or violet.
Chromium, violet.
Copper, blue.
Iron, green to violet.
Nickel, blue to green.
Manganese, pink.

In chemistry with metals we can see many colorful reactions, sometimes the colors can give us a clue as to what metals may be in solution, but by colors alone we only have clues, and many times these colors could fool us if we tried to determine what we have by color alone, many times colors can be meaningless as to what we may have in solution.
You cannot always judge a metal or a solution by color of a chemical or the color of a reaction.


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## chemistrycoach (Jan 3, 2014)

Again thank you Butcher, your a big big help for newbies like me.


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## chemistrycoach (Jan 5, 2014)

this is a great forum and i'm proud of being a member here , through the years i learned a lot from our moderators and members, i like to test things first hand to experience some reactions of what just i read here in advices, 
recently from old broken high carat jewelries i cut a gram of broken necklace,, from this i put the gram in 200 ml of aqua regia
heated it up and wait for 15 minutes to consume it all...now i have a pregnant solution of whatever it is in the metal no Dennoxing

i made stannous chloride about 100ml

flush the stannous to my aqua regia in my small beaker
almost instantly the color of my solution turned dark, but about 30 seconds or so the dark solution clears slowly forming a gel like flocculation moving around inside the beaker as it gets smaller and smaller as if dissolving away, now as it dissolves some different colors of material falls down like snow.. this materials shine back with the flash of the camera like christmas lights with different colors very amazing to watch, 

as the dark gel dissolves completely a rain of yellow color glitter falls down and settles at the bottom of the beaker

i would ask experts advice or people with enough experience to help explain this reaction. do i have precious metal in my solution ? if so what happened to the stannous i introduced ?

Ps, this is only some test to observe reactions for documentation and future references, not for recovering or any interest of commercial value, thank you very much forumer's and more power to everybody


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## chemistrycoach (Jan 5, 2014)

added pictures


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## Harold_V (Jan 5, 2014)

Perhaps I misunderstood what you said, but I got the impression that you applied stannous chloride to your beaker of gold chloride. Assuming I'm right, please take this in the spirit in which it is offered. 

*That's stupid!*

Do not test your solutions by contaminating the entire lot. Take a sample (a single drop, which you'd get with a glass stirring rod), which is then placed either in a cavity of a spot plate, or on a piece of white paper (a fitler paper will serve well), to which you'd apply a drop of stannous chloride. There's 'nothing about a stannous chloride test that you can't learn from that simple process---that you can possibly gain by contaminating the entire lot. 

You haven't lived until you try filtering a solution contaminated with tin. 

Have you read Hoke's book? Doesn't appear (from your comments) that you have. BIG mistake. My advice to you is to get on with the read. 

Harold


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## chemistrycoach (Jan 5, 2014)

hi Harold, i realized yes that is very stupid of me to do that, to begin with the necklace i am pertaining too is not yellow at all
it is a white silverish metal, 32 grams to be exact, i would like to sell it to a scrap jewelrer, the problem is i might get cheated because i see no gold color in the necklace, so i tested a piece of it in AR realizing that it would show me a clue of whats in the metal, if theres gold , palladium, or platinum, i know that i throw away a gram of that metal by doing so, and still not to have a clue whats in it, so anybody here who could tell me if i got something in that solution and what happened in the solution, even just a suggestion in what you saw is a very big help for me. i did not throw the solution away,

Ps, i have a hard copy of hokes and trying to learn something everyday by reading it in my free time. thank you very much.


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## butcher (Jan 5, 2014)

Stannous chloride in the solution added tin.
Tin in a solution of dissolved gold give problems when trying to recover or test for the gold, it can make filtering a problem. Basically making a mess of the solution.

The stannous chloride test is done with drops of liquid (drops from our gold solution we wish to test) either in a white spoon or a spot plate, or on a Q-tip or filter paper, then drops of stannous chloride are added to this, to see if there is a reaction or change in color to violet, or another color if possible Pt or Pd.

When you dissolved your necklace in aqua (I do not know the Karat or if it was gold, or if you removed base metals with nitric first...), (so some of what I say here is assumption on my part), you probably also have base metals in solution, and the stannous (or tin) you put into solution could have precipitated some base metal from solution, gold if in solution could be reduced but it would not precipitate, it can just form colloids which are now hard to detect in solution, still so small you cannot see them, they would be so small they will pass through a filter (that is if you can filter the tin gelatinous compound which can also trap some gold), basically now you have a mess that can be hard to deal with.

It does not look like you have much solution, what I would do is evaporate it down slowly to a very thick solution, once it was thick I would sprinkle in some NaOH powder (to lower acidity and to convert acids to salt water sodium chlorides, where you can remove as much chlorides from the values as possible, gold in an incinerating roast with chloride can make some of the gold volatile and go up with smoke), stir, just add enough NaOH to make a clear solution of salt water at around PH7, and let metal powders settle, use a pipette to decant the clear salt water, rinse the sludge several times with plenty of water heat to a boil and then let it settle again, and decant salt water (test the rinses for gold), once the powders are rinsed of chlorides as much as possible.

Slowly on low heat evaporate the liquid from powders (very low heat until the powders dry), once dry crush the powders and raise the heat, the may fuse and become soluble again, if they do lower heat so the syrup does not form popping bubbles splashing values from your dish, and continue on low heat till dry again, crush them to powder, and now raise the heat to high, you may see smoke of acids or salts leave the powders, bring the powders up to a glowing red hot and keep them glowing red hot while stirring them, if your hot plate or whatever you heat on cannot get this hot a propane or other torch can be used, stir the powders while still red hot, we need to expose these red hot powders to oxygen so that we oxidize the base metals, many time the powders will darken from oxidation.
I prefer to do this in a Corning-ware pyroceram dish.

Now let the powders cool, Here I normally use water from a spray bottle and rinse down the sides of the Dish, cover the powders in water and heat to a boil lower heat so powders will settle then decant the rinse water with my suction tool and pipette.
Then I cover powders with HCl and bring to a boil, lower heat so powders settle well, I try to keep solution warm so I can decant any dissolved lead chlorides, but want all of my gold powders to settle well, (but the powders not being stirred by the heat), decant the HCl wash, if this wash shows a lot of color, I will do another HCl boiling hot wash, if not much color I will do several boiling hot water washes again to remove any dissolved base metal chlorides, decanting the water washes hot also helps if there are lead chlorides involved.
Now I can start over with what I wish to do with these gold powders.

If I wish to do a nitric treatment to remove base metals here, I would repeat the process above, and remove chlorides as much as possible and incinerate again (but without the HCl boil), this is to remove traces of chloride that would dissolve gold when I used nitric acid.
Or
If I was satisfied I had base metals removed, (and decided I did not need a nitric treatment to remove base metals but not dissolve the gold), then I would not have to repeat the incineration process that removed the chlorides (the second time), and could just move on to aqua regia where I dissolve gold.

Study Hokes book keep reading it until what you read makes sense to you, sometimes we have to read something a couple of times before the concepts she teaches becomes clear to us, there is so much information in the book it is hard to grasp everything by just reading it once, much of what you learn from the book is an overall picture of how to recover and refine, understanding concepts that may not be clear when you first read each page, but later become clear to you, as you contemplate the overall book, of how she chooses different methods for different types of material, or may deal with different materials differently because of the other metals involved, or does a process differently to remove troublesome base metals... 
After you read it a couple of times much of this whole picture is normally seen much clearer.

Practicing the getting acquainted experiments in Hokes book, and the experiments of testing metals in solution are very valuable tools, these give you hands on knowledge of how the metals react, she also encourages reader to come up with more experiments of their own, like the ones she describes in her book, doing that and doing experiments of your own, you can learn a lot about recovery and refining, and reactions you may see as you do, learning what may work and what may give you troubles.

Hoke's also has a book for testing jewelry for precious metals, with these tests you would not of had to dissolve your necklace to test it. that book can also be found on the forum as a free download file.


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## chemistrycoach (Jan 5, 2014)

I really admire how you explained things very clearly Butcher, hokes book
Is realy very helpfull same as people like you teaching patiently and very clearly 
Once in a while people must teach us what we did wrong in refining gold and from that try to correct
It the next time ..im off to the mini lab to follow your advices. . Thanks a lot and more power


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## butcher (Jan 6, 2014)

I would read Hokes before working too much more in the lab, and then when ready for the lab work on doing the experiments in the book, this way you get a better understanding of how not to make mistakes, and understand better how to get out of them if you do.


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## chemistrycoach (Jan 10, 2014)

Hello Butcher, moderators and forumers , please help me answer some questions 

Why does my gold in aqua regia does not test positive for gold in stannous t
In Q tips but test positive very dark violet in spot plate?
And does not react when cold bout reacts when heated in the same spot plate stannous testing with the same gold chloride? I did not yet dennox. But even so it gives dark purple colors when hot
And no reaction when cold.

Also does to much iron in aqua regia solution will result violet purple in stannous testing ?

This are separate cases needs knowledgable assistance please

Thank you very much guys


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## butcher (Jan 10, 2014)

I do not have a valid answer, I am unsure why the reaction would occur on a spot plate, but not on a Q-tip, it should show up in either one, how much gold do you have in solution? Is the Q-tip and the spot plate the same solution? You say the spot plate tests positive while hot but not when cool, if this is the same solution maybe the Q-Tip is cooler from evaporation of liquid?
I presume the color you see in the spot plate is purple and not brown or just some dark color.


Stannous chloride can reduce gold, but if there are oxidizers they can dissolve it back into solution, you can have a test, that will give a test positive reaction, and then you can watch the purple disappear (when there is still some nitric acid present), the heated reaction may be reducing gold, and then it redissolves because of free nitric when cooled (just a guess here).

2AuCl3 + 3SnCl2 <-- --> 2Au + 3SnCl4
Notice in the above equation, I have a double arrow, on the left we add stannous chloride to a gold solution the reaction moves to the right, but if there is free nitric acid it may move back to the left, or it may not even try to move to the right of the equation, if the stannous chloride cannot reduce the gold, the free nitric acid keeping the reaction to the left keeping the gold in solution

I have had a stannous chloride test on a gold solution turn so dark I could not tell the true color, (it would almost look black), what I do when this happens I will hold the Q-tip over fumes of some evaporating aqua regia the damp fumes would dilute the color where I could see what looked black was actually a dark violet, the fumes lightens the color in the reaction. I have not tried it, but it might also work by opening the bottle of HCl and holding the Q-tip over the fumes emitted from the open HCl bottle.

I suspect free nitric acid may be giving you the problem you see.

Iron will not give the violet color with stannous chloride, although I would not doubt an iron solution may change colors when stannous chloride is added, iron can give several colors to solution depending on the oxidation state of the iron solution, the stannous chloride being a reducer for several substances.

stannous chloride acts as a reducing agent, reducing silver and gold salts to the metal, and it can also reduce copper(II) to copper(I)., or can reduce Iron(III) salts to Iron(II):

SnCl2 + 2 FeCl3 → SnCl4 + 2 FeCl2 

The iron solution or copper I chloride will not turn violet. the solution of copper can darken towards brown.
The violet color in the reaction we see called the purple of Cassius is specific to colloidal gold as far as I know other metals do not give this color of solution when tested with stannous chloride.

.


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## rickbb (Jan 10, 2014)

The only problem I see in your pictures is, your not wearing GLOVES!

Please wear them, and eye protection, especially if your going to post pictures. Other people new to these process might get the wrong idea from pictures like that and hurt themselves.


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## chemistrycoach (Jan 10, 2014)

Thank you for the reply Butcher, i guess there is an over excess of oxidizer in my Sol...
That is giving me problems ... here is the color of my AR Sol when sncl is introduce , one without light
And the other with light shine.


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## chemistrycoach (Jan 11, 2014)

yes rickbb will do. thank you for reminding.

Butcher, here is the picture close up of my shallow test plate. it is like black violet and when i let shine on it is like burgandy violet i think its gold reacting with stannous.. am i right ? is this the violet purple reaction ?

another thing is when i leave the test plate for 10 seconds or more it goes back to the aqua regia color

you are right teling me i have free nitric, is dennoxing the only way to eliminate the free nitric? are there any optional method?

thanks a lot


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## butcher (Jan 11, 2014)

chemistrycoach,

It is hard for me to tell by the picture, but that looked like a beaker full of solution (not a few drops of solution in a spot plate), it also looks like you have something floating around in solution which almost looks like flakes of gold or something, that violet color does look like it can be the violet colloidal gold.

It looks to me as you do not have a spot plate, but have added stannous chloride to a considerable amount of your gold solution, this would tie up a lot of your gold in this solution (making it very difficult to recover the gold from it).

It only takes a few drops of the solution to test for values, this can be done in a spot plate or a white plastic spoon, or on a Q-tip or filter paper...

How much solution is in this Beaker (or what is it in the picture?), is this all of your solution you added the stannous chloride to, or is this just a portion of your original solution, what is that floating in solution?

I cannot see what you are doing, but something does not look right here.


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## chemistrycoach (Jan 11, 2014)

Hi Butcher 

yes i do not have a spot plate , i would get it tommorrow on my way home, i use a very shallow watch Glass
my AR solution is dirty because the metal i put in AR came from a dore bar, but i drilled the whole bar to get samples first like ribbons and get 100 grams of drillings and dissolved the base metals in 50/50 hot nitric acid, decanted it and the sponge black and browm ( i dont know how much it weighs ) i then dissolve in AR

it was a test to see if there is gold or platinum in the dore bar

this is the same material and different test i did and the result, i could not dennox because of a very large amount of AR in my beaker that might take me a long time to dennox it three times like hokes said.

the test i showed you is a few ml of AR and a few Ml of dissolve tin metal in hcl mix in a shallow plate and in a beaker

i know it is not right to waste gold chloride if the case maybe and i will never use this style of testing again

this is one of my personal projects doing smelting with gold ores

what concerns me is dennoxing my whole beaker maybe 250 ml of AR solution

i guess i use to many acid ( AR )


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## Palladium (Jan 11, 2014)

Urea will neutralize nitric acid. Add until no more fizzing is observed, filter, and then drop.


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## chemistrycoach (Jan 12, 2014)

thanks palladium, will get urea to take away nitric or i may be doing in small batches to speed up denoxing


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## butcher (Jan 12, 2014)

You can do a couple of things to get rid of the free nitric acid, add gold and heat to use up the free nitric acid (Harold's trick), or use sulfamic acid, or the evaporation, or a combination of these.

I personally do not like Urea, and if you do suspect platinum using Urea could complicate its recovery.

You should be able to determine if you have gold or platinum with your spot plate tests, after De-NOxing the solution to be tested (you can use sulfamic acid to remove nitric from a small sample to be tested), (sometimes if the solution to be tested has a couple of metals that react to change color of the solution being tested it can be hard to tell, by using a spot plate you can test with a copperas crystal (ferrous sulfate), the gold if in solution will precipitate as brown ring around the copperas crystal, (this precipitates gold from the solution in this test, leaving the solution in this test barren of gold), then we can move the gold barren solution from this test to another well in the spot plate and test it with stannous chloride for platinum.

I thought you just had gold in solution, I did not know you were working with a Dore bar, how does your solution filter?
The solution does look dark, like there are other metals in solution, in the one picture I do see a dark yellow that does resemble gold in solution, but iron can also can look like gold in solution. It also looks concentrated, it is hard to tell what is in solution by just looking at it, that is where our testing helps us see what we really have.

Testing will be important, you need to learn to do it properly, otherwise you would still just be guessing.

The solution looks fairly concentrated, that is good for De-NOxing the solution.

But you will want to dilute and let it sit overnight (for silver or lead to settle),(a little sulfuric acid or sulfamic will help if lead is in solution), and filter before trying to precipitate your gold.


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## chemistrycoach (Jan 12, 2014)

you are right butcher, i got a little solution and put it in a test tube then add ferrous sulphate crystals then at the bottom of the test tube i can see the ferrous sulphate crystal with a dark brown ring forming around it ( not in the center but forming around it )

you mentioned that base metals mix with gold in AR solution pushes the gold out of the sol..this probably is my case

when i dissolve base metals in 50/50 nitric, i felt it is never 100% that i cleaned it all out, traces of base metals may be in my sponge when i introduce it to AR

that is why i am saying that sometimes i dont get a violet result in stannous chloride testing when my solution is cold
it maybe because the gold ions had turned into metallic gold push out by traces of base metals in the sol

and when i try to heat it again the AR dissolves it back into the sol as ions giving me a positive violet reaction

the picture where you thought gold flakes floating around the AR sol when i introduce stannous may also be true

as this yellow particles shines back in camera flash ( i think metallic flakes reacts that way )

the gold maybe reducing and redissolving over and over again because of the traces of base metals

but i really took out base metals first using dilluted hot nitric acid, although some traces must have been left behind

the dore bar consist of copper and if there is gold or platinum group that maybe in there 

that is why im posting pictures about my stannous chloride testings asking help about color reactions that im getting
from expert advice on our forum, before i process doing furthermore refining

i will follow advises to see reactions or non reactions

this is the picture of some yellow flakes floating in the test, some gold may be colloidal and some maybe starting to reduce, this things happen mixing us up as Butcher said complex base metals with precious metals in one same solution


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## chemistrycoach (Jan 31, 2014)

Hi there again, i precipitated gold using copperas green crysrals dissolve in water 
and Hcl
After the brown cloud i found feather like soft thin films of golden colored metals tiny bits
Of it.. it is metallic and yellow metals like really yellow golden color, i decant the spent solution after checking 
In stannous and heat it again with 50/50 nitric but it only shines more and not affected
..does anybody has a same reaction i got when using ferrous sulphate? Thank you forumers and moderators !


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## qst42know (Feb 23, 2014)

Have you considered a fire assay? It is often the prefered method for testing complex dore. Metals that complicate wet testing can be reliably removed. If I'm not mistaken dore can be melted with fluxes that aid in the elimination process.


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## chemistrycoach (Mar 7, 2014)

Thank you for your advice qst42know, i fire assayed a 50 gram drill sample of my dore bar and there is a 1 gram
silver bead that was inquarted with the lead, after that we go t
o cupelation today
Can i ask ? Can we test palladium in stannous chloride if it was dissolve in 50/50 nitric?


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## chemistrycoach (Mar 9, 2014)

Hello everybody, just want to ask if palladium is dissolved in nitric acid can we 
Test the presence using stannous chloride ?


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## butcher (Mar 9, 2014)

Why not use DMG.

I believe you could test it with stannous chloride, (I have not tried it).
You could take a sample and drive off nitric with heat, add a little HCl, proceed to drive off remaining nitric from the sample and do the stannous test.

I suggest you get some DMG for palladium testing.


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## chemistrycoach (Mar 9, 2014)

Thank you Butcher , i will first try your first suggesrion then find DMG in chemical supplies


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## butcher (Mar 9, 2014)

Adding HCl would precipitate silver chloride if silver is in solution (very possible), so you may need to transfer the solution to another well of the spot plate, or remove solution from the silver chloride, during your test.


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## chemistrycoach (Mar 9, 2014)

Copy that Butcher , i will follow the instructions ,will update what will the test be,thanks again


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## chemistrycoach (Mar 10, 2014)

yesterday i followed Butchers suggestion getting a few sample of the nitric acid that i suspect that there is palladium dissolved in it, had it evaporated to syrup twice adding HCL everytime , then tested it with stannous chloride the result is somewhat dark brown? so i tried to dillute a little sample in a little beaker and tried some cementation putting in a copper wire that was hammered flat just for a test, i dip it to the brown solution and waited for an hour and try to see what was going on by recovering the copper back, it did turn to something like blackish dark brown or black? i let it dry and look at it under microscope, i was surprised to see such many colors in magnification but in plain eyes view it was rather blackish, reminds me of leaf gliding with precious metal films or thin foils? can anybody here knows what am i seeing? why so many vivid colors attached to the copper in magnification? thank you very much guys!


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## chemistrycoach (Mar 10, 2014)

this are the other pictures of te copper wire in magnification


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## butcher (Mar 10, 2014)

Nice picture of reflection of light off of metal crystals (valuable metal crystals).


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## chemistrycoach (Mar 10, 2014)

thank you very much Butcher !, i think i will have our dore bar XRF first to give us an approx content of alloyed PM's
this was only a trial if i could cement values out using copper, it is a nitric solution so i guess gold does not include here in what is cemented, there aare some black powders undissolve in the bottom of the beaker that must be gold or PGM

i am sharing this pictures to our members so they could have an idea of such reactions


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## chemistrycoach (Mar 13, 2014)

hello friends , just wanting to share digital zoom picture of platinum mixed with little palladium or vice versa? cemented on a flattened copper tube, i owe a lot of my learning to all members and moderators here, it is a privilege to be a part of this forum thanks to all !


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## saadat68 (Dec 14, 2018)

Hi
Assume we have some gold alloys with very little silver so we don't need inquartation
For example:
75% gold
20% copper
5% silver
Or
40% gold
5% silver
55% copper

As you see we have a lot of base metals so it is not good digest them in aqua regia directly
1- Can we digest these alloys in nitric first to rid off base metals? (without inquartation) I ask this question because percentage of gold is high
2- For dissolving a gold alloy( without or little silver )in nitric, Is there any rules about minimum and maximum percentage of gold? For example we can't dissolve 22 karat gold in nitric because gold percentage is high and we can't dissolve bese metals and silver this way 

I didn't search many because I don't know what I must search
Thanks


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## 4metals (Dec 14, 2018)

One way or another you will have to dissolve out the copper. This material looks like karat gold used for jewelry and you are correct there is low enough silver so you do not need inquartation. I would be dissolving this material in aqua regia and dropping the gold with metabisulfite. If you need higher purity a second digestion and a drop with oxalic acid will do nicely. 

The collected chlorides can be reduced with either caustic and glucose or sulfuric and iron. With only 5% Silver there should be little gold entrapped by encrustation if you start by melting and pouring cornflake shots prior to your digestion the first time.


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## saadat68 (Dec 30, 2018)

4metals said:


> One way or another you will have to dissolve out the copper. This material looks like karat gold used for jewelry and you are correct there is low enough silver so you do not need inquartation. I would be dissolving this material in aqua regia and dropping the gold with metabisulfite. If you need higher purity a second digestion and a drop with oxalic acid will do nicely.
> 
> The collected chlorides can be reduced with either caustic and glucose or sulfuric and iron. With only 5% Silver there should be little gold entrapped by encrustation if you start by melting and pouring cornflake shots prior to your digestion the first time.


Thanks
You said little gold will entrap in silver chloride *even with 5 percent silver*
1- So at the end of the process we will have silver chloride with some gold?
2-How must recovery this undissolved gold? Add to next inquartation batch or dissolve chlorides to aqua regia several times until all of golds dissolve to the solution?


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## 4metals (Dec 31, 2018)

Any silver has the potential to encrust and trap some gold. Generally with karat gold anything with 9% or less Silver content I would do a direct dissolve in aqua regia. But I say that from the perspective of a refinery equipped to properly assay the incoming lots and segregate them accordingly. 

All scrap coming into a properly run refinery is melted and sampled, this way the customer, if they are there to witness, gets a sample as well as the refinery gets a sample. Your question pertains to a gold and silver alloy so only gold and silver will be tested for. When a refinery collects enough bars to process a refining lot, the bars are melted together based on the assay of each bar. All bars are melted and mixed well, sampled one more time, and poured into water to produce a shot which looks like popcorn or cornflakes and has a large surface area to aid in digestion. The thing you are trying to attain is a lot with 9% or less silver content. 

When you are trying to refine a bar with say 20% silver, aqua regia will not work. But if you have enough other bars with less than 9% silver, you may be able to add this high silver bar to the melt because what you need is the end alloy which will be put into aqua regia to be 9% or less silver. If you make up a spreadsheet for your bars to be tracked, you can mathematically determine which bars can be added to a melt and still be safely under the 9% as long as you have gold and silver assays for each bar. 

I have seen tumbling systems actually be more effective against silver chloride encrustation because the tumbling and grinding action actually breaks up any potential encrusting lumps of silver chloride. These systems can actually produce acceptable results with up to 12% silver content. 

The silver chloride accumulated from these digestions is rinsed well and reduced to a metal which is melted into anodes for a silver cell. This is how most refineries recover any entrapped silver. 

Usually a refiner will establish an "acceptable" accountability for a refining lot and if the lot produces the accepted quantity of expected gold, the silver chlorides are not processed individually. But until the results of a refining lot are quantified and accepted by the boss, the residues from the refining lot should be kept separate in case the accountability is not met. This makes isolating and finding any missing values easier. 

In any refining operation of even moderate size, there is a quantity of gold that isn't worth chasing on a lot by lot basis. With the method stated above, large "losses" can be isolated quickly and the smaller "expected" losses can be processed in due time to recover any gold lost to the silver encrustation. That produces the most cost effective use of a refiners labor and time.


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## saadat68 (Jan 1, 2019)

Thank you 4metals


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## Jeman (Mar 12, 2019)

Hi, anybody can assist me regarding gold solution?
The problem is after I put 2 spoon (10gm) SMB and I add more SMB for the next but I take a wrong chemical in to the solution (stannous chloride) after that the reaction is color of solution change to dark green and got the brown dust, so how to dissolve the matter? Thanks


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## Lino1406 (Mar 12, 2019)

Filter to get the brown dust. Water rinse. Check if it is pure gold or contains white tin dioxide


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