Silver Nitrate and Gold nuggets

[wct0415]

Memorial Day weekend My first experience with Processing Silver Nitrate and removal of Gold
In my first post ever I detailed what would be my first attempt at refining. It was with some sterling silver spoons that had Gold nuggets soldered to them. Questions to follow, please bare with me.
Processed them in 50/50 Nitric and distilled water (no heat) outside of course, It process took about 48 hours to completely dissolve the lot, and could have probably been quicker but I went under slightly on the 50/50 solution and added more as needed until everything had been dissolved with the exception of the gold. What I had remaining was a very dark bluish brown solution (somewhat murky) with a whole lot of gold chunks (nuggets) and a fare amount of brown powder settled at the bottom, just as one would expect, however would have expected it to be much clearer blue. I suspect the murkiness my have been from the many decades of built up polishes and such that were in the crevasses of the silversmith working. Please correct me if I am wrong on this assumption.
After my first filtering it seemed to clear up the solution to a point but is still very dark bluish brown and not real clear.
Keeping the gold and brown powder in the container and washing it several times and finally transferring it to a small container.
During the above started a second silver nitrate process with some sterling medallions and a couple of badly abused 90% coins and a Canadian 80 % dime. This time it was as one would expect very clear deep blue with some more dark settlement at the bottom.
My questions are:
1) Do I need to continue to filter my first Silver nitrate to try to get it to clear up?
2) Do I cement the silver from both processes separately or mix together and run it as one.
3) And the gold nuggets, since there is numerous inclusions within the nuggets in the form of crystals refine them with an AR process along with the brown settlements from both batches, or process them differently.

I know there are a lot of questions but if at all possible to simplify things my inclination is to processing combine both but the nagging question in my mine is the first process (murky solution) and if I have something else that needs to be done to clear up this silver nitrate. Also since I have some gold settlement at the bottom of both batches can they be refined further with the nuggets in an AR process or should they be processed differently.
One last thing is on the nuggets where they were soldered to the spoon, is black and didn't come dissolve out during this whole process. In a silver solder what alloy could possibly cause this to happen, and my assumption is some of the settlement is of this same alloy.

Thanks Bill

No problem can be fixed before a solution is formed. No solution can be formed until the underlying problems are clearly identified.

 

[Harold_V]

Without addressing your questions as asked, I'm going to give you something to think about.

Any material that is refined benefits from incineration. I can't think of anything that is ignored more than that process, unless it's the lack of testing with stannous chloride (when appropriate). Incineration eliminates many of the problems one encounters, but never identifies, in processing.

When gold gets soldered to silver, it's a pretty safe bet that at the juncture of the soldered joint, there is migration of gold to silver, and silver to gold. When this material is dissolved, the ratio of gold to silver can make dissolution difficult, even impossible, as gold moves beyond 35-40%. When you have that experience, you're likely to find an area that is black, or dark bronze in color, where silver has been leached by nitric, to the point where the remaining gold isolates the material from the acid in use.

Same thing happens in reverse, if you process gold with AR cold, and there's too much silver present. In that case, a film of silver chloride forms over the gold, isolating the material from the acid, so no further digestion is experienced. When it's done with heat, the film may be a light green/gray color. When done cold, it may be just an off white color.

Murkiness in your solution, especially if it has a hint of purple, may well be traces of colloidal gold. To find colloids in your circumstance would not come as a surprise to me, considering items have been soldered and atoms of gold are likely separated from the joints. Migration of one element to another would explain how the gold gets so finely divided.

Assuming that thought is correct, it isn't beyond expectation that the murkiness you witnessed is caused by traces of gold, along with contaminants that may have been eliminated in incineration. That being the case, collecting the solids by either allowing them to settle, or by filtration, is suggested. Once gathered, they should be incinerated to dull redness, then screened. After screening, a rinse in hot HCl is suggested, which will remove unwanted substances, and yield a solution that filters well after the values have been dissolved in AR.

Assuming one were to follow these processes, testing with stannous chloride, to insure that no values are lost by washes, would be mandatory.

Harold

 

[wct0415]

Thanks Harold
So I take it when you have said: "Any material that is refined benefits from incineration" your ref is to heating any solution in the process of refining greatly benefits the final outcome and thusly expedites the process. So am I correctly summarizing your recommendation that I should try to clear up as best I can with filtration a time or two and collect all of what I can gather from my murky solution and add it to all the other brown gold that has dropped and put it a hot solution of HCI (Hydrochloric Acid).
So from what I have read on the forum my next process would to drop the gold (what ever may be left) suspended in the silver nitrate before cementing out the silver.
Secondly refine the gold nuggets in an AR solution along with everything filtered from above to assure the best possible purity of Gold. If all else fails I can take all the metals dropped AU/AG melt them all together and perform an Inquartation process. Chalk this up to experience and move on to my next attempt at success.

Thanks again Harold.
PS; I will do a stannous chloride test to verify the contents of my solutions and expected outcomes

 

[eeTHr]

Since nitric doesn't dissolve gold, there won't be any gold "in solution." All the gold should settle to the bottom, either overnight or within a week to ten days if it is really small particles. What I have done is let it settle overnight, then decant the solution to another jar, and process the sediment.

Let the jar of this solution that you decanted, sit for a week or so until it is clear, then decant and process that sediment. Then cement your silver from the second decanted solution.

If you have colloidal gold suspended in your decanted solutions, those particles are very, very small. Unless the solution is a deep purple color, it won't amount to any significant value, and if they join with your silver when you cement, they will separate when you run your silver through an electrolytic cell to purify the silver. This colloidal gold is also the purple color produced by stannous chloride, when gold is present, when testing your solutions.

Incineration is a dry process. You heat the powder, as Harold described. You can search "incineration" for more details on the best ways to do it.

Remember the purpose of each step, and the purpose of each acid.

Decant, rather than filter, whenever possible. Or else you will end up with lots of small gold particles stuck in the filter papers (save them if you do, for recovery later). The gold will appear as black or grey smudges within the papers.

 

[Militoy]

Thanks Harold
So I take it when you have said: "Any material that is refined benefits from incineration" your ref is to heating any solution in the process of refining greatly benefits the final outcome and thusly expedites the process....

I'm certainly not qualified to put words into Harold's mouth - but I believe when he recommended "incineration" - he meant exactly that - reduction of organic wastes to ash and gas by combustion. That usually involves the burning of the material using a whole lot of heat - not just heating up the solution.

EDIT - Ah - I noticed eeTHer already pointed out that incineration is a dry process. Like he suggests - take advantage of the search function.

 

[Harold_V]

Thanks Harold
So I take it when you have said: "Any material that is refined benefits from incineration" your ref is to heating any solution in the process of refining greatly benefits the final outcome and thusly expedites the process....

I'm certainly not qualified to put words into Harold's mouth - but I believe when he recommended "incineration" - he meant exactly that - reduction of organic wastes to ash and gas by combustion. That usually involves the burning of the material using a whole lot of heat - not just heating up the solution.

That's correct. Anyone that takes solids from one acid (nitric, for example) to another acid, and hopes to not dissolve values, is making a mistake by not incinerating. I recommend the material be taken to a dull red heat, so carbon will combust and be eliminated.

Harold