Silver hiccup

[nh6886]

I Have been having great results recovering silver with processes learned here on the forum. I have been getting better than 99% Ag with the trace being copper. I am going to attach a couple of pictures here of what I have been seeing and what I got this weekend. The source material has not changed that I knew of and the process I am using is the same. I cement with copper buss bar that I heat to red then quench before use. I am using approximately 1.25ml of 68% nitric/Distilled water per gram. I say approximately because at times the reaction stops before all the nitric is added. I also add1% volume of H2O2 (3%)
I add the silver to the Distilled water and H2O2 then heat to near boil.
I add the nitric about 20% at a time with new additions added only when reaction slows. As the third addtion slows to near stop I add heat until reaction stops before adding the fourth. Often I don't add all of the fith volume. When the reaction stops I let stand overnight and decant into a Buckner funnel. I drop with copper bus and three hot water washes seem to do the trick. I test the last wash with household ammonia for copper.

I have three questions,
Why the green color of this solution?
What are those long crystals?
What should I do now?
If I do this right the first pictures will be of what I have been getting the last three the results I ended up with this weekend.
Thanks for looking and I welcome all comments
John

 

[nh6886]

Dropped silver

 

[nh6886]

Dried powder

 

[nh6886]

Weekend results

All the Best
John

 

[butcher]

A green color can come from free nitric in solution, or from (brown) palladium in solution.

I do not know what the long crystals are, but lead salts can sometimes form long crystals.

If silver nitrate solution is concentrated the silver can also form crystals.

It sounds like your doing a good job, are you diluting the solution before cementing with copper?

I am not sure what you mean by what do I do next? looks like you have studied enough to know what to do. I do not see much I could add.

You can test to see if all of the silver is out of solution by taking a small sample of solution and adding salt or HCl to see ifsilver chloride forms

I would just wash the silver well, dry it out, use it to inquarter gold, or melt it, you could sell it, or refine it in a silver cell.

The copper nitrate could be saved for another project, added to a stock pot, or used to recover a portion of nitric from it useing Laser Steve,s suggestion of driving copper out of solution with a grafite anode, or treated it for waste (after you test it for values).

 

[etack]

What is the feed stock? Nickel is green in nitric. If they are contacts this what the green more than likely is.

Lets melt a bar :lol:

Eric

 

[nh6886]

Thanks Butcher,
It has been a lot of fun getting to this point. I started doing these about ten grams at a time until I could get the results I wanted.
I was asking the what next question about the green solution. I was in hopes that maybe someone had seen this before. Whatever the hair like crystals are I don't want them in the melt if I can get rid of them first. I can take a sample and try a very hot water wash to try and get rid of lead if that's it?

Eric,
The feed stock is contact point. I tested them early on due to the warnings of cadmium but found none. The big surprise to me was that I try to be very methodical about the process and this one came out very different.
I have been trying a bit pouring bars but more practice is in order. It makes me feel like the three bears story mold to cold, mold to hot, all fun though and unlike wood I never have to through my projects in the burn pile :lol:

Thanks everyone,
John

 

[nh6886]

Butcher
I added the silver nitrate crystal just for fun, I had to leave my solution unexpectedly and when I returned to it the next morning theses were growing, they were cool to look at and easy to deal with.
All the best
John

 

[etack]

If the silver is from contacts then nickel is what I would suspect. AgNi alloys are common in contacts. additionally if you did any that where AgWx contacts the W is sintered with Ni as the binder.

Your AgNO3 crystals remind me when they first grew on me. I was freaked out and had to g and Google AgNO3 crystals to see what they looked like. :lol:

thanks for the bars I love silver the best. I think you need to heat the mold some more and keep the silver hot when pouring it.

Eric

 

[Auful]

Butcher
I added the silver nitrate crystal just for fun, I had to leave my solution unexpectedly and when I returned to it the next morning theses were growing, they were cool to look at and easy to deal with.
All the best
John

Do you think the AgNO3 crystals formed because the solution was saturated with AgNO3. If not, what might be the cause? Temperature? The solubility of AgNO3 is rather high, isn't it?

Would somebody please direct me to a thread that discusses the function of H2O2 as it relates to silver refining in nitric acid? H2O2 must aid HN03 in the conversion of silver to AgNO3, I presume. If that's the case, I am curious why HNO3 would need assistance in that regard, already being a strong oxidizer. Thanks!

Matt

Edit: added my theory what H2O2 might accomplish

 

[Anonymous]

It would be easier on the eyes and neck if the photos were rotated to how a person should see them (upright) instead of having to turn their head to the left to make out the image.

Make sure your images are upright before uploading them.

Kevin

 

[butcher]

The little hydrogen peroxide is added to help to extend the nitric acid in solution, this works two ways, the water in the hydrogen peroxide helps to dilute the solution, and by helping to convert NOx gases back to useable nitric in solution, instead of leaving solution these are used to dissolve more silver.

Diluting helps to keep nitric in solution also a couple of ways, a concentrated solution vapors off more acidic gases, and NOx gases from solution, a dilute solution these gases mix with the water in solution helping to lower the evolution of these gases.


The water and the oxygen that forms from the hydrogen peroxide forms water and dissolved oxygen in solution.
H2O2 --> H2O + O2

The decomposition of nitric acid form NOx gases, there are many of these that evolve from solution with nitric acids reaction on metals but the primary ones that concern us is the clear colorless NO and the red brown NO2, here the water and oxygen in the diluted solution from the hydrogen peroxide helps to convert these gases back into nitric acid, to do more work instead of leaving the solution.

H2O2 --> H2O + O2

2 NO + O2 --> 2 NO2

2NO2 + H2O --> HNO3 + HNO2

I think I remember Noxx posting a patient on this a few years back (but with my memory I can be wrong).

 

[nh6886]

Butcher,
Thanks for the H2O2 answer. I know I have read your explanation before and I was looking for a link to the thread but you beat me to it. Your explanation previously is why I do this but I did have to see for myself so I set up two flasks with and without the added H2O2 I could observe the slower evolution of the red brown NO2 in the flask with the H2O2. I also use a glass bulb for a cover and a good bit of condensates and drips back into the solution.

Hi Matt,
To answer your silver nitrate crystal question yes the solution is very consentrarted with silver I figure the math as close as I can and there is always a little silver left undigested when I'm done, even if I have to add some. The only way the solution held this much silver was being heated so when I had to shut down it cooled slowly sitting in a sand lined glass frying pan down to around 38 degrees in my carport so they had hours to grow.

Hi Kevin,
I would be glad to know how to do that but when I added it it was oriented correctly so it's in the attaching that I screwed it up? If you or anyone else would like to share the key to doing it right I'm all ears. Thanks for looking

All the Best
John

 

[Auful]

Butcher: Thank you VERY much for the thorough explanation. How does one calculate the appropriate amount of H2O2? What effect does over-use have? I also wonder what are the effects of over-dilution of this reaction, or is this the same question?

nh6886: Thanks! If you merely raise the temperature (ie to room temperature), will the crystals redissolve, or do you need dilute with water as well?

Matt

 

[butcher]

I normally do not calculate use although you can if you wish.
I guess I just go by what I see, if I am heating a solution of aqua regia dissolving gold and I see red fume evolving I will add a little water till the fume's subside, if I add a little more water I do not worry the heat will just evaporate it off anyway, same thing with adding a little peroxide to nitric acid to dissolve silver, the heat drives off the added water and oxygen in the peroxide either reacts or escapes as gas, these solutions are normally concentrated to the point that there is no water in the solution any way (actually normally to the point all of the free acid is reacted with metals also).

I suppose if you want to calculate the formula for this, you would write the formula for the reaction, you will have a gas on one side of the formula after the arrow, balance the formula (same amount of atoms on both sides of your arrow), then use the periodical table to get the atomic weight of each of the elements, in grams per mole, add up the total molecular weight for that compound, to get grams per mole.
Now I would do this again but adding hydrogen peroxide into the formula balance the formula (this time where there is no unreacted NOx gas in the formula after the arrow).

Now we would also have to figure any water in the acids used and the water in the peroxide, included in this formula, using specific gravity of the acids, and reactants, molecular weight of the acid (or peroxide) in our formula (and the percentage in our acid, which also gives us percentage of water in the acid at the concentration of acid we use), here we are also interested in the water in our formula as a reactant.

You can get an example of how I might calculate this here:
http://goldrefiningforum.com/phpBB3/viewtopic.php?f=33&t=16744

I can do this but I am not that good at it, (it takes me a lot of time strugling through it), I have just barely learned it from studying a couple of chemistry books, and trying to learn this on your own with a couple of chemistry books is a little confusing at times but doable, I am still a little baffled about all of the math molarity normality density specific gravity and so on, what to use where and why, what to divide into or multiply and why, I know it cannot be that hard to understand this, but I seem to have trouble with understanding the explanations the chemistry books use, and sometimes it baffles me when they add some number in a calculation, and do not say where that they got that number from, and why (I guess I have to understand every little detail and the why of how something works to be able to understand it well) I have a mechanical mind, I have to know how every part moves and know what it does to understand how it runs.

You can find examples in some second hand chemistry books, of how to do this, or find it on Google, finding an author who explains it best to you, will make it easier to learn, I just have not found the author who speaks my language yet (and it is taking me some time to learn theirs).

 

[nh6886]

Matt,

That's a good question unfortunately I did both so I don't know if I needed to add any water, I don't think so. However since I was considering harvesting some of the silver nitrate crystals I sprayed the silt off them with distilled water (adding water to the equation) then saw that there were some dark spots in the crystal base and decided that I would grow some out of a filtered solution if I wanted them. So I combined the lot, warmed it up until everything that was soluble was in solution. Then decanted the bulk of the solution through a Büchner funnel with a medium speed filter paper, and poured the dregs in last as it filters pretty slow. Cement with copper buss bar.
There is so much great information here on the forum it's amazing. That is where every bit of my process came from. The list of credits would be longer than reasonable but when I am looking for information I advance search Butcher, KADriver, Gold Silver pro, 4metals, Geo and of course Harold and Lazersteve. The list goes on.
I read for months before doing anything other than acquiring and breaking down material and to tell you the truth I still haven't touched my really high grade stuff. I enjoy the learning part of this as much or more than anything else.
All the Best,
John

 

[Auful]

Butcher: thanks for steering me in the right direction!

John: I am amazed at this forum. It should be retitled "Gold Refining University." :lol: I am trying to learn and there is a LOT to learn about these processes. It seems the more I learn, the more questions I have. Thanks to everybody who imparts their knowledge!

Matt

 

[nh6886]

Almost the end
I heated the solution with the long crystals and added 50ml distilled water. The crystals went back into solution. I tested a sample with HCL to check for silver and it came up barren. I decanted hot through a filter as far as I could then added the silver cement did two very hot water washes and set aside this solution. I cleaned up the silver as discussed and melted the powders into a bar that tested better than 99.5% Ag. :lol:
When the solution cooled the long needles grew again and I am going to try to filter team out so I can identify them if I do I will post the result here.
Thanks to everyone for there input.

John

 

[FrugalRefiner]

Eric,
The feed stock is contact point. I tested them early on due to the warnings of cadmium but found none.

John,

I'm interested in how you tested your contacts for cadmium. Can you tell me your process?

Thanks,
Dave

 

[nh6886]

Dave,

I am lucky enough to have access two a couple of Niton (XRF) X-ray florescence guns. These are widely used for PMI (positive material Identification) I will attach a screen shot in case you or anyone else is unfamiliar with them.
This is from a 100AMP Cutler Hammer 3 pole breaker as you can see these are silver (Ag) and Tungsten (W).

All the Best,
John

Edited for wishful thinking