# Ugh Help!!



## Cuffs (Aug 10, 2017)

Greetings all,

First let me say I've found quite a bit of useful info here.
I am in the pawn business I process a fair amount of old and scrap mixed karat jewelry. After studying hokes book, or at least the sections concerning what I am doing. I feel pretty confident I am on the right path. Made a few mistakes the first couple times but was able to recover, learned from it and now I am within a half % of calculated weight in the end. With that said I have a buddy in the same business that has decided to try his hand at it. 

This is how it happened as relayed it to me.
He started with 1250 grams of mixed karat jewelry. AR solution as best he can remember 400 ml of Nitric acid 1200 ml hydrochloric acid said he had good reaction everything dissolved. This is where it went off the rails for him. I am not sure why but he diluted it several gallons of water 8 plus gallons at this point said he used urea to try and kill off nitric acid doesnt know how much he used exactly. ( I dont use urea I get the silver chloride out reduce d it down with heat then precip the gold) He then used about 5 pounds of SMB in two five gallon buckets he got some gold out but based on my math is about 7 oz troy short. He called me asked me what to do and I have no idea at this point so told him to stop until he can get some proper help. Any thoughts would be appreciated.


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## anachronism (Aug 10, 2017)

Hey Cuffs

Firstly welcome and thanks for a good detailed intro post. If you're already between half a percent of expected yield then that's pretty good going well done.

Your friend should not have premixed the AR. It appears that he had far too much Nitric left and using Urea and diluting isn't the best way to go. Things have moved on since Hoke wrote her book. Whilst there are a whole host of amazing things she wrote about, times have simply moved on and in some cases there are better chemicals and processes available. Removal of excess Nitric is one of those things. As GSP would say, learning to use "just enough" Nitric is the way to go and frankly he's right but that comes from experience.

For example using Sulphamic acid, or as you Americams call it Sulfamic acid. Do a search on this on the forum and you'll probably see where your friend went wrong. You sound like a guy who likes to learn properly so give that a go and come back and ask for more info as you need it.

Good luck and happy to help.

Jon


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## Cuffs (Aug 10, 2017)

Jon, Thanks for the welcome. 
Let me say in full disclosure that I had a gentleman whom I bought the shop from teach me for 2 years. He had been working with metals and chemicals for a very long time so my success is his he made start with small quantities and learn and work up from there. I wish he was still around to help my here to help my buddy

Thanks 
Steve


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## 4metals (Aug 10, 2017)

I think the fact that you were within 1/2% of your expected recovery is good and totally within the realm of possibility that your silver chlorides are holding the missing gold. It is not uncommon for the gold to be retained as metallic gold shielded from digestion by silver chloride. Did you dissolve solid pieces of jewelry or was it melted together and poured as shot before digestion? 

As far as your friend is concerned, I believe he used far too little aqua regia for the weight of gold he was processing. 1250 grams is 40.28 ounces. If I were digesting this quantity of gold I would be using a bit over 5 liters of acid total. Generally karat scrap consumes about 1 liter of acid for every 7.5 ounces of metal dissolved. I suspect he had a dark nasty looking concentrated acid and some of his values cemented and are mixed with his chlorides because the volume of acid he used is not enough to hold 40 ounces. And, while his issue is different than your issue, did he melt the scrap together and shot it before digesting?


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## Lino1406 (Aug 10, 2017)

"based on my math is about 7 oz troy short." Please give the math

Source material
Weight - Karat
1.
2.
3...

Dry silver chloride weight:


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## anachronism (Aug 11, 2017)

4metals said:


> As far as your friend is concerned, I believe he used far too little aqua regia for the weight of gold he was processing. 1250 grams is 40.28 ounces. If I were digesting this quantity of gold I would be using a bit over 5 liters of acid total. Generally karat scrap consumes about 1 liter of acid for every 7.5 ounces of metal dissolved.



If he hadn't said that everything was dissolved I would have suggested this too. Then again you're approaching this from the "too much metal in the liquor" angle 4metals?


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## g_axelsson (Aug 11, 2017)

Have you done a stannous test on the remaining liquid?

Göran


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## 4metals (Aug 11, 2017)

There is a point when the base metals begin to displace the noble metals that dissolved so that there are PM's in solution (and thus a positive stannous test) and PM's have dropped. If this is the case the dropped PM's are fine mud, not unlike silver chloride. So the stannous isn't the answer to finding all of the gold. When you saturate the acid with metals and they start to drop out, you are walking a fine line. That is why you need enough acid to hold all of the metals that are soluble, otherwise you run the risk that some (but possibly not all) of the PM's drop out. 

If the material the friend processed was jewelry, I assume (although assumptions can be dangerous) but there is usually silver chloride left after the digestion. So everything couldn't dissolve. But everything could have been converted to a paste like consistency like the silver chlorides which are mistakenly assumed to be ALL silver chlorides. 

That's my theory and I'm sticking with it.


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## 4metals (Aug 11, 2017)

I realized Goran is thinking the gold is still in the acid from the original dissolve which was dropped but possibly not completely dropped. This is also a possibility but I have to go back to the point that 1.6 liters is not enough acid for 40 ounces of alloy.


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## 4metals (Aug 11, 2017)

> Then again you're approaching this from the "too much metal in the liquor" angle 4metals?



Jon,

We all know that there is a finite quantity of metal that can go into solution, and after that is exceeded, noble metals start to come out and are replaced by base metals. I hope this is true because if it isn't about 14,000 threads concerning cementing need to be deleted from the forum!


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## anachronism (Aug 11, 2017)

4metals said:


> > Then again you're approaching this from the "too much metal in the liquor" angle 4metals?
> 
> 
> 
> ...



Hehe :lol:


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## g_axelsson (Aug 11, 2017)

I wasn't concerned with a lot of gold still in solution and I think your explanation is sound, 4metals.
But testing the solution could eliminate 8 gallons of solution from the suspects. And if the acid was totally spent there could still be gold in solution as SMB needs acidic conditions to work.

As the original poster claims to have read Hoke, making stannous and testing should not need any more explanations.

In the end the gold would end up in three different locations, precipitated clean gold, in solution or in undissolved solids. If it isn't in any of those places there were less gold at the start, maybe a math problem or fake jewellery.

Göran


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## Cuffs (Aug 11, 2017)

Sorry for the delayed response been busy this AM.

After reading some of the questions i made contact and asked exactly what he did to the best recollection he has.
I will stop by his shop Saturday to see first hand what hes got.

He told me Wednesday he used 2 cup of nitric and 6 cups of Hydrochloric. When I spoke to him we discovered his measuring cup is actually a 2 cup measuring device and he filled to overflowing.

Approximately 900 - 950 ml Nitric
Approximately 2800 - 2900 ml Hydrochloric 

614.2 g 10K
623.7 g 14k
11 g ?? probably 10K

No test at this point.
And doesn't know the weight of silver chloride, will get that today.
Can we put silver in a pan with low heat to dry it quickly for weighing?

Let me know anything else y'all need to know.

Steve


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## Topher_osAUrus (Aug 11, 2017)

Dont dry the silver chloride. It will be next to impossible to convert it back.

And is your math taking into account the tolerance allotted for jewelery? .5k variance, plus another .5k if it is soldered (most all jewelry is)
Sad to say, more times than not they go under a karat instead of over.


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## 4metals (Aug 11, 2017)

Was the scrap melted together and poured into water before digesting it in acid? For mixed karat goods this is helpful because it evens out the silver which may be higher in some karat alloys and lower in others. 

Use a cast iron frying pan and some sulfuric acid to reduce the silver chloride without drying it. Then you can dry it because it is metallic.


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## Lino1406 (Aug 12, 2017)

260.5g + 363.8g = 624.32g that what was expected? 7 troy ounces short that's around 217g missing


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## Cuffs (Aug 18, 2017)

SORRY IVE BEEN SO LONG ON REPLY BEEN A BUSY WEEK.

lINO, ONCE THE STONES WERE REMOVED HE WAS EXPECTING 615. WHAT HE HAS IS 441.

4METALS, no it was not melted prior doesn't want to damage gemstones.

He watched a video on how make and test with stannous says the remaining liquid test is still pretty dark indicating there is still gold in solution. So now that its already been heavily treated with SMB where to go from here?
Is it feasible to reduce it down to a heavy liquid and try extraction again?

PS I never did get a chance to go by and see it in person.

Steve


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## Cuffs (Aug 18, 2017)

Forgot to tell y'all he said he had massive reaction when adding the SMB i guess that suggest the Nitric was not neutralized?

Steve


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## Topher_osAUrus (Aug 18, 2017)

A dark stannous test could be a false positive.
Is the "dark" result brown or purple?
Brown is false positive, purple is gold

Id suggest adding copper in to cement out any remaining values in solution. Adding more chemicals to reduce what may or may not be in there isn't going to help.


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## snoman70 (Aug 22, 2017)

As topher said. Dark has to be described better. Brown is the sulfur from the smb. I'd heed his advice, add a piece of copper to the liquid. Suspend it so it's under the liquid but not on the bottom. Let it sit. Collect any precipitate after a couple of days. Test remaining solution and treat as waste if test is negative for values, which it should be. Now you'll be working on a smaller scale. Don't let him measure nitric with a two cup measuring cup!!


Sent from my iPhone using Tapatalk


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## anachronism (Aug 22, 2017)

Cuffs said:


> Forgot to tell y'all he said he had massive reaction when adding the SMB i guess that suggest the Nitric was not neutralized?
> 
> Steve



You can't make that assumption because SMB reacts in acidic conditions. Could you define a massive reaction for me please? Do you mean lots of frothing or do you mean lots of precipitation?


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## nickvc (Aug 22, 2017)

One question leaps to mind after 4metals asked if the scrap was melted together, is there any undissolved metals in the bottom of the beaker or mixed in with the silver chloride?


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## 4metals (Aug 22, 2017)

That is why I asked if it was melted together before processing. The fact that there were stones was not mentioned. When doing stone removal it is unlikely that all of the pieces have the same % silver. Usually a few pieces get coated up with chlorides and trap undissolved gold. But many facts in this thread were mis stated. Did everything dissolve? Impossible if there was silver. 

If we had accurate facts this thread would be done and all of the values would have been recovered already. But if we don't get the proper information what we say becomes pointless. 

Maybe the OP would care to start over, or better yet, let his friend tell the story.


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