# Determining the contaminant.



## autumnwillow (Mar 13, 2017)

From my previous refining compared to now I have been getting poor results. 

This was a gold refined previously. 



This is the gold that I am getting now. 



I have ruled out the following so far:
Steel mold contamination - I am now using clay crucibles until I get a nice surface finish

HCl not pure enough - I switched suppliers and the hcl that was provided was not fuming. So I assumed it to be contaminated or not pure. But this does not seem to be the problem as I have tried to HCl from another supplier. Although I did get better result now. 

Filter paper - I had to switch to a #1 filter due to supply of #2 was not available. I was able to get my hands on a #2 though. Same result. 

Come to think of it I was using a #42 filter paper. Maybe that's the problem? 

Or maybe because I switched to propane/oxygen? Which I doubt could be causing the problem.


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## Geo (Mar 13, 2017)

The bottom button doesn't look like it was in a liquid state very good before it cooled. It may not be enough heat.


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## autumnwillow (Mar 13, 2017)

No the bottom one was a good refine. It was poured in a mold. The first picture is the problem. It has an orange stain.

Edit to add. Pictures mixed up in tapatalk.
The button/disc is the problem.
The other one was poured in a mold which is better. No surface stains (signs of oxidiation).


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## anachronism (Mar 13, 2017)

How do you know it's not as pure please? Are you just judging it by its look or have you got a proper test result?


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## autumnwillow (Mar 13, 2017)

anachronism said:


> How do you know it's not as pure please? Are you just judging it by its look or have you got a proper test result?


Just by the way it looks.
Pure gold will not have any form oxidation on its surface.


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## autumnwillow (Mar 13, 2017)

Here's a higher resolution picture.


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## g_axelsson (Mar 13, 2017)

Show us a picture of the melting dish/crucible used.

Göran


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## autumnwillow (Mar 13, 2017)

This type:



I let the gold cool off there, smash it and retrieve the gold. I'm using a new one every time just to properly rule out whats causing the problem.
So far this is the 2nd button produced. Could it be the clay crucible? Maybe I should use silica?

I didn't dilute the solution to twice its volume, could it be this one? I didn't do it to save space for wastes processing as most of the washings will most likely double the volume. I'll try to dilute it on the next refine.

Water quality? Could a water with 3ppm reading from a TDS meter from an RO system cause the problem?

SMB used was at 62g, gold refined was only 49g, will 13 grams of excess SMB cause problems? This was processed in nitric first then AR.


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## autumnwillow (Mar 13, 2017)

Oh wait, you wanted to see the flux color/stain. I'll check on that tomorrow but if I remember it right I think it was clear, not purple.


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## g_axelsson (Mar 13, 2017)

Yes, pictures of the molten borax in the clay crucible would have been good, if it is clear or slightly purple it shows a low level of contamination. Dark borax is usually a lot of oxides.

What was the starting material?

Since you said the borax was clear, I wonder if it might be a slight palladium contamination. I don't know if it would show up as a slight discoloration on the surface. Maybe someone else can pitch in on that.

Göran


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## anachronism (Mar 13, 2017)

As Goran said what's the starting material please. 

Too many variables in here until we get more relevant data. By the way your crucibles don't look bad at all.

Edit: Goran is he's melted it properly there would be hardly any borax to show. The red tinge looks like collodial gold which is fine.


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## autumnwillow (Mar 13, 2017)

Starting material was jeweler's bench sweep. I had a similar result from karat scrap.

Those crucibles are cheap but they are porous. I still prefer the silica crucibles but I won't be using one until I get a proper finish. I usually only use this type of crucible when I have soda ash in the flux.

Let me try to enumerate my process:
1) Inquart then shots.
2) Digest in nitric until no red fumes (2:1 water/nitric, then 1:1 nitric)
3) Wash 3x with hot water
4) Add HCL, add nitric
5) Sulfamic while hot
6) Cool the solution to precipitate contaminants
7) Filter
8) Add SMB in a cold environment (I put the flask in a bowl filled with ice)
9) Wash 2x hot water, cold water, cold HCL, cold water, hot water, cold water, cold ammonia, cold water, 2x hot water.


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## g_axelsson (Mar 13, 2017)

anachronism said:


> As Goran said what's the starting material please.
> 
> Too many variables in here until we get more relevant data. By the way your crucibles don't look bad at all.
> 
> Edit: Goran is he's melted it properly there would be hardly any borax to show. The red tinge looks like collodial gold which is fine.


If I'm not mistaken the picture of the crucible is a similar one and has not been in use.

He wrote that he had to smash the crucible to get the gold out.

Göran


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## autumnwillow (Mar 13, 2017)

Could small stains in a flask cause such? I'm also thinking it could be this one, I'll try to clean all the flask tomorrow before proceeding with the next lot.

Borax color is black, I just checked the button now and it was visible at the bottom of the disc.


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## g_axelsson (Mar 13, 2017)

Inquarting should remove palladium, I don't think it might be palladium any longer.

Small stains in flasks and beakers shouldn't be a problem either. Just keep the beaker where you precipitate the gold and clean it spotless. But it never hurts to have clean glass ware.

Black borax in the crucible points to a lot of oxides in the final melt. Try to just melt borax without gold and see if it also turns black, then there is probably contaminants coming off the clay crucible.

I'm just throwing out a wild idea, I don't know even if this is possible...
Maybe contamination from the crucible. Are you using an oxidizing or reducing flame when you melt your gold? The red color of the crucible looks like iron staining. If some iron oxides are dissolved in the borax it might be reduced into iron and contaminate the button, showing up again when the surface is cooling down with oxygen from the air around it.
If this is the problem then it would be easy to just use more oxygen in the torch. Any iron oxide will stay in the borax.

If you pluck the button from the crucible while the borax is still fluid then you don't need to crush your crucible every time.

You can compare the color of your borax with the melting dish I'm using to melt fine gold. This was a first melt and the small prills were collected in the next melt. When a dish gets too contaminated I use it for inquarting or other melting to collect any remaining gold.
http://goldrefiningforum.com/phpBB3/viewtopic.php?f=61&t=19622&p=235911#p235911

Göran


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## autumnwillow (Mar 13, 2017)

Ahhh. Come to think of it your crucible idea could be right. I may have solved the problem by replacing my Hcl supplier but if the crucible that I was using is contaminated I would probably not ever solve this problem. I use an oxidizing flame but there may be not enough borax used as I usually only use a pinch for 24k gold melts on a silica crucible. Ill try to use a lot of borax on the next process.


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## anachronism (Mar 13, 2017)

I think you're over complicating this gents if you don't mind me suggesting that.

Willow what was the base material please?


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## g_axelsson (Mar 13, 2017)

anachronism said:


> I think you're over complicating this gents if you don't mind me suggesting that.
> 
> Willow what was the base material please?





autumnwillow said:


> Starting material was jeweler's bench sweep. I had a similar result from karat scrap.


At... http://goldrefiningforum.com/phpBB3/viewtopic.php?p=268387#p268388

Göran


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## Topher_osAUrus (Mar 13, 2017)

Maybe another dissolution of the gold powder would solve your problem. After the washes, of course.


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## autumnwillow (Mar 13, 2017)

Topher_osAUrus said:


> Maybe another dissolution of the gold powder would solve your problem. After the washes, of course.



I was able to produce buttons like this before:



Using the same process. No 2nd refines. Some of the materials that I am using have changed so it has something to do with them. The feedstock is also the same.

Edit to add:
The orange tint is just from a light source. That button is pure yellow. The button/bars produced now is clearly off from the buttons that I used to produce before.


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## anachronism (Mar 13, 2017)

Sure, but that willow pattern on the button above is a sign of contaminants too, no pun intended of course!

Edit- from what I've been told that's possibly PGMs


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## autumnwillow (Mar 13, 2017)

anachronism said:


> Sure, but that willow pattern on the button above is a sign of contaminants too, no pun intended of course!
> 
> Edit- from what I've been told that's possibly PGMs



True, that could have been Pt/Ir. That was my very first refine. I only have 2 pictures of gold that I have refined before. How about the 2nd picture of my first post? Judging it by the way it looks does it seem to have any contaminants?

I can't really assay my gold properly though, can't find a proper assay lab in my country that can perform a fire assay/ICP/etc. I also don't have the equipment to perform a fire assay.


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## autumnwillow (Mar 13, 2017)

I scanned my phone and this is another picture of a bar I used to make:


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## Topher_osAUrus (Mar 13, 2017)

A second dissolve will help give clues to what the contaminant is. From the color of the solution after precipitation.

The excess smb could have caused contaminants to drop with the gold, or they could have got dragged down mechanically.

When gold is in powder form, a redissolve and precipitation can be done within a day. 

I cannot say for sure that it is your problem, but, a single refine is sometimes considered to just be "recovery"

The first bars you produced could have ended up more pure because it may not have had the same contaminant, may not have been overdosed with smb, or you may have just got lucky. Not sure :lol:


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## anachronism (Mar 13, 2017)

The second pic of the first post looks fine to me to be honest. You say you poured that into a mold? 

I think you're worrying over things you don't need to worry about because none of it looks badly contaminated. 

By the way over dosing with SMB doesn't really cause that many issues. You're cleaning your gold with HCl and water washes anyway.


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## justinhcase (Mar 13, 2017)

Is the question that important?
I get paid the same for 999 Au as 9999.
And the difference is only really quantifiable by Masgas Spectrometer.
E.G. Identifying accurately such small trace impurity's. 
Easy to find out ,cost you about £116.


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## anachronism (Mar 13, 2017)

Or just go to a mate who has an XRF- that's what jewellers would use to buy your gold so that's all the test you need to pass.

As pointed out though does it really matter- because you'll only get paid on the gold content anyway.


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## justinhcase (Mar 13, 2017)

anachronism said:


> Or just go to a mate who has an XRF- that's what jewellers would use to buy your gold so that's all the test you need to pass.
> 
> As pointed out though does it really matter- because you'll only get paid on the gold content anyway.


XRF's can give you a ruff idea of content,but get very easaly confused.Not some thing I put my money on with out backing up with a solid recovery.
give me a good lab any day.


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## anachronism (Mar 13, 2017)

If the guy paying you is basing his price on an XRF then if you have had it XRFed already you know where you are pitching from. XRF's aren't bad. Provided you know how to use one and understand the limitations.

The guy who buys my gold is worth over £40M from using one to make his buying decisions and that's a pretty good benchmark.


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## justinhcase (Mar 13, 2017)

anachronism said:


> If the guy paying you is basing his price on an XRF then if you have had it XRFed already you know where you are pitching from. XRF's aren't bad. Provided you know how to use one and understand the limitations.
> 
> The guy who buys my gold is worth over £40M from using one to make his buying decisions and that's a pretty good benchmark.


If I am being paid it is for fine gold,no assay or XRF required.
XRF good for screening hole alloys,no good for widdeling out the little bit's of value that may be hidden.
I only use to check for rhenium in spent super-alloys my self.
No doubt your friend who made him self 40M had a very good margin,probably more than enough to make up for a large statistical error.
If you want to cut some throats a slightly miss calibrated XRF if a gold mine literally.People just do not question what they see on a tiny screen.
Test by every method available to you,old school fire assays are bomb proof and cost a fraction the cost of XRF once you look at the kit.


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## anachronism (Mar 13, 2017)

justinhcase said:


> anachronism said:
> 
> 
> > If the guy paying you is basing his price on an XRF then if you have had it XRFed already you know where you are pitching from. XRF's aren't bad. Provided you know how to use one and understand the limitations.
> ...



Firstly, he actually works on approximately 1.5%-2%. He doesn't need to cut anyones' throats because he's probably one of the most trusted gold dealers in the whole of the UK. People do get successful without cutting peoples' throats.


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## justinhcase (Mar 13, 2017)

anachronism said:


> justinhcase said:
> 
> 
> > anachronism said:
> ...


I said that he would have a good margin not that he cut throats.
Then I said if you wanted to cut throats it was a very good way to do so.
Why so defensive?we are discussing the merets of differing analytical method's.
All the best buyers I know of use fire assays ,you can see it along with the melt charge.
When I see 1-2% margin I expect to see substantial processing charges as well.
Unless you are known to them quite well and they trust your product.
If you are dealing with some one unknown then the cost of a drill sample and fire assay tend to be charged to the client.
Do I know you under an other board name?


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## autumnwillow (Mar 13, 2017)

I do not sell gold at the moment as we are in need of it. We are actually buying.
I own a jewelry shop and we only want to use the finest gold possible and If ever I decide to sell gold I can ask for a premium since most of the gold traders here supply about .990 - .995 gold purity at 24k market price.


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## kurtak (Mar 14, 2017)

justinhcase said:


> Do I know you under an other board name?



Justin

You know full well who Jon is :!: 

At least you should considering he allowed you to use his license to make a deal a couple years ago - a deal you could not make with out a license

We wont go into how that deal ended

All I am going to say is that if you are trying to bait Jon to respond in a negative way in the hope to see him banned - NOT a good Idea --- we just recently had another member try that - it did not end well for that member

Just as a reminder

:arrow: http://goldrefiningforum.com/phpBB3/viewtopic.php?f=68&t=23062&p=241824&hilit=Justin#p241602

:arrow: http://goldrefiningforum.com/phpBB3/viewtopic.php?f=60&t=23208&p=243616&hilit=Justin#p243600

:arrow: http://goldrefiningforum.com/phpBB3/viewtopic.php?f=50&t=22831&p=239812&hilit=Justin#p239705

My point --- play nice :!: 

Kurt


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## allenp (Mar 14, 2017)

You may have a bit of silver left which can cause the effect. After you add the sulfamic acid you should triple the volume with very cold water to cause silver chloride to precipitate.


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## justinhcase (Mar 14, 2017)

kurtak said:


> justinhcase said:
> 
> 
> > Do I know you under an other board name?
> ...


Thank you for confirming that this is John I will ignore him form now on..
And you are some what misinformed.
I was going to rout quite a lot of e-wast through the gentleman concerned.As you know I can not stand the stuff my self let alone waste my time trying to process 99.9% of it so it was important to find some one that would not try and under pay me for small increments.But would let a lot build to the point of maximum return.E.G. Tunn lot's.not fart around with every little bit.
But I found his attitude abhorrent and I detected several methods of manipulation being use by him.
So the work went to a much larger concern who quite happily let me operate under there license, under much better terms,and no petty problems.
If John engages me despite the fact he knows who I am may be I am not the one trying to cause friction.
Security and conflict resolution is my main trade.
May be people should start running back ground checks on thous they intend to do business with as I do.


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## kurtak (Mar 14, 2017)

justinhcase said:


> Thank you for confirming that this is John



Not sure who you are trying to fool here because it has been made "well known" who Jon is since his return under his new user name :!: :!: :!: 

as I said - "You know full well who Jon is" :!: 



> And you are some what misinformed.



I am sure you have your own side to the story - but based on the 3 links I provided I have cause to believe other wise



> Security and conflict resolution is my main trade.



What's your point ?

If you wish to discuss this further - I suggest we take it to discussion in PMs --- there is no need to further distract from this thread &/or cause disruption on the forum

My ONLY point in my first post was that you do know who Jon is (as I say - that has been made WELL KNOWN) & therefore your last response to Jon has every "appearance" of "baiting" --- which ultimately leads to disruption --- if I am wrong in my conclusion you certainly have my apology ! 

My intent was simply to stop what "looked" liked something that could develop into a disruptive argument 

Again - if you wish to discuss this further - I suggest we take it to a discussion by PM

Kurt


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## anachronism (Mar 14, 2017)

autumnwillow said:


> I do not sell gold at the moment as we are in need of it. We are actually buying.
> I own a jewelry shop and we only want to use the finest gold possible and If ever I decide to sell gold I can ask for a premium since most of the gold traders here supply about .990 - .995 gold purity at 24k market price.



Hi Willow I see where you say that you can ask a premium but if that's the case you're going to need a way to know that your gold is above this. It's entirely possible that it's over 99.9 right now, but then again it might not be. What it looks like doesn't really cut the mustard at the high end of purities. 

Jon


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## Lou (Mar 14, 2017)

Follow the wash procedure and be sure to remove lead. Do not over use reducing agent and you will make high purity gold.

A final sonication with 70% hot sulfuric acid can be used to clean up the gold markedly in purity.


You can remove the ugly appearance with ammonium chloride sprinkle when the gold is hot. It is a very fumey process.


Feathering in your gold is due to Pt. 

Oxidation color can be due to most likely copper or iron. My suggestion is to wash your gold powder much better as most impurities are by physically absorbed processes rather than included/co-reduced with the gold.


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## autumnwillow (Mar 19, 2017)

Solved.

The 2nd refine was due to clay crucible contaminants as what Goran have mentioned.
We only changed crucible and followed the same process using the same chemicals.
Also my previous posts regarding steel mold contamination is ruled out as we also poured this in the same steel mold.
HCl is the contaminant in our process, supply is from a swimming pool chemical store. Must be not that pure, everytime we use this we get a very strange AR color (cloudy and greenish).
We used the HCl from a drug store supply instead.

Results:


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## glorycloud (Mar 19, 2017)

Nice looking loaf of Au bread there autumnwillow! 8)


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## anachronism (Mar 19, 2017)

Sorry but that gold is no purer than the previous pics. The surface visibly shows this. For reference look at my profile picture. I don't get how impure HCl was the issue when your precipitant is selective and your wash process further takes more impurities out.

Can you share how you came to this conclusion please?

Jon


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## goldsilverpro (Mar 19, 2017)

anachronism said:


> Sorry but that gold is no purer than the previous pics. The surface visibly shows this. For reference look at my profile picture. I don't get how impure HCl was the issue when your precipitant is selective and your wash process further takes more impurities out.
> 
> Can you share how you came to this conclusion please?
> 
> Jon


I would agree with Jon. Doesn't look too pure to me either - dull color, no crystal, no pipe. I would try to clean it up in the melt (simplest way) by alternating a pinch of niter (2 or 3 BBs) with a pinch of borax. Do this until the molten gold forms a mirror-like surface, with no white film. Shouldn't take more than 2 or 3 applications. If it doesn't clean up, re-dissolve in AR and re-purify it.


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## 4metals (Mar 20, 2017)

> A final sonication with 70% hot sulfuric acid can be used to clean up the gold markedly in purity.



Lou mentioned this above but it seems nobody bit on it so maybe I should explain the process and the value of the technique in cleaning up gold that isn't quite up to standards.

About 5 or 6 years ago there was a discussion amongst the moderators about getting high purity gold in a single pass. Lots of suggestions were discussed but most involved chelation and that always throws a monkey wrench into waste treatment so, for me, it isn't worth the effort. Especially if there is something simpler. 

I mentioned a method I had used which I called pulping. Basically it involves tumbling in a violently agitated tumbler, gold sponge and adding 25% concentrated sulfuric acid to 75% hot distilled water. I was working on a large project and looking to gas gold in a single pass from direct aqua regia digestions and get a purity of .9999. The way I was doing it was to gas the solution with SO2 and stop before the drop was complete. The gold that drops first is cleaner and the gold assayed high first drop. The balance of the gold in solution was filtered off and the gassing was completed, resulting in the balance of the gold which required a second pass or re-refine. I put this gold aside and continued work on the first drop high purity process I was hired to implement. I have worked with gold all my adult life and because of that I have a sizeable mental block assigning value to piles of in process gold. So while I was blissfully playing with the single drop process, a pile of gold was accumulating which was worth well over a million dollars, probably closer to 2 million. The boss was apparently watching and noticed, after all it was his money. He came to me and asked me to please make that gold sale-able. Like yesterday if possible!

I took a sample of the sponge before treatment and then used the pulping process in a large oblique barrel with a blade mixer and did the sulfuric water thing and ran it for 15 minutes. Filtered, rinsed, and resampled the gold. The gold before the process was .999+ and the gold after the process was .99999. This was run in an ICP by difference. I had used the process before and knew it worked but never actually quantified how effective it was in the lab. Although the first few runs came out 5 nines, I would be satisfied claiming 4 nines which we consistently hit in production. 

Since this was the gold dropped at the end of a SO2 drop it was the dirtiest of the gold dropped. I realized we could drop it all with gas, forget the extra filtration step, and use the pulping to process the entire lot and bring up the purity. This process was effective at bringing .999 gold up to .9999 gold easily without major waste treatment ramifications. 

Lou had never heard of this before and since he has a well equipped lab with all of the big boys toys he gave it a try. The thing is he didn't have the oblique barrel and he didn't have the gold quantity to require the big barrel anyway so he used ultrasonics to provide the agitation. He used the ultrasonic to process lots up to 2 kilo's or so in size of sponge if I remember correctly. And his testing also verified the usefulness of the process. 

So now, with a more detailed description of sonification as Lou called it, a good rinse protocol, followed by the sonication process, this may be the answer to cleaning up your gold sponge before you melt it. You need to do this in a beaker because most ultrasonic cleaners will not withstand the hot sulfuric. And I think the time requirements go up with an ultrasonic as well, maybe Lou can refresh my memory on that detail.


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## autumnwillow (Mar 20, 2017)

SMB is not selective. 
Hcl was clearly the contaminant as this is the only thing we changed. It required more than 4:1 ratio. If I recall correctly we used about 12:1 hcl nitric ratio for digestion to complete when using the contaminated hcl. 

Gold has no pipe due to slow cooling. 
This gold was very shiny. As very pure gold is prone to scratches even with just a plastic brush it resulted in a dull color. Crystals are visible if you zoom in.
Pipe did attempted to form as shown in the bottom of the bar. 

I will try sonification with sulfuric acid on the next lot and see if there is any improvement. Anyone reading this thread should be aware of the danger of using sulfuric acid at that concentration.


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## anachronism (Mar 20, 2017)

Given that you don't get all the metals out when you use SMB it is therefore by definition selective. Yes you can get some drag down using it however it's still selective. 

I appreciate that you think your HCl is causing the problems however I would respectfully have to beg to differ. 

I've had exactly the same contaminated "look" on gold myself and it's turned out to be PGM contamination as has already been mentioned in this thread. Using a different precipitant on the second refine usually works for me to get the gold pure. 

Jon


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## autumnwillow (Mar 20, 2017)

I'm not asking for any appreciation. 
We alloy the gold ourselves and know when there is PGM present in the lot. Most of what we processed that resulted in gold surface tarnishing did not have any PGM present. 

Again. Only hcl was changed in the chemicals used and we got a better result.


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## anachronism (Mar 20, 2017)

I believe something has got lost in translation here.

That given, it's apparent that my help is not wanted, which is fair enough so I'll bow out.


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## autumnwillow (Mar 20, 2017)

My bad. Must've read it the wrong way. Driving and reading isn't good.


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## salman1122 (Mar 21, 2017)

how much smb should be added to AR?


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## upcyclist (Mar 21, 2017)

salman1122 said:


> how much smb should be added to AR?


Until gold stops precipitating out when you add it. Waiting for the last addition of SMB to settle out, having clean glassware, and having good lighting all help in this respect.


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## autumnwillow (May 1, 2017)

Bump this topic.

The problem was filter paper grade. Used a #1 filter paper and moved to a #2. 

I'll try to order a #5 next and might as well go for a larger buchner funnel as this is really our current bottleneck in the process. Any tips on the size that we need? We are currently using a 125mm.


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## Lou (May 1, 2017)

Check out Belart.


We have a couple that are about 3' in diameter that work nice.


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## 4metals (May 1, 2017)

As Lou said Belart makes nice tabletop buchner funnels, but they are available with a perforated plate and a Fritware porous plate. Make sure you get the perforated plate. That is the plate with the drilled holes. The fritware porous plate does not have visible holes and as they age and you get sloppy, the pores get clogged and are tough (if even possible) to clean out. 

You can choose either plate fixed (welded in) or removable. I have always had good luck with a welded in plate but some refiners swear by the removable plates as well, so it is a personal preference. 

Belart claims the removable plates are for precious metals recovery but if you are accumulating values that have gone through your filter media (or under the edge of your filter media) you need to work on your technique.

The holes in the perforated plates are available in two sizes. If you choose the larger hole size you may need to back your filter paper with cloth sheet material to prevent the vacuum from blowing a hole in your paper (if filtering hot this is a bigger issue). 

https://www.belart.com/buchner-table-top-funnels.html

Another nice tool if you are using a tabletop buchner is a vacuum plate. It is basically a rigid piece of polypro that covers the top of the funnel and is sealed with a gasket. In the center is a fitting to connect to a suction hose which allows you to pull a vacuum on the filter and put the hose in the liquid you want to filter. The suction will pull the liquid through the hose and into the funnel and you will not have to lift and pour. iShor makes one of these systems but they are super simple and easy to make your own for substantially less money. 

https://www.ishor.com/shor-buchner-vacuum-plates-and-gaskets


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## Topher_osAUrus (May 1, 2017)

I hope justin sees this reply.
Brilliant stuff.
He was just talking about something identical to the polypropylene cap and hose design recently on another thread.


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## justinhcase (May 1, 2017)

Topher_osAUrus said:


> I hope justin sees this reply.
> Brilliant stuff.
> He was just talking about something identical to the polypropylene cap and hose design recently on another thread.


Yes that is perfect.
I have bid on tabletop buchner funnels but had not thought about simply using a plate and four threaded bars to form a vacuum.
Much thanks.


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## autumnwillow (May 1, 2017)

The 300$ 26cm inside diameter is similar to a 240mm 130$ Buchner funnel? 
I guess I'll stick with the funnel type first not unless we process heavier lots. Silver can wait. Heh. I'll go buy the 36" when our lot sizes increases. Hopefully the 240mm will speed things up. Thanks for the advice guys!

Sent from my SM-G920F using Tapatalk


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## autumnwillow (May 1, 2017)

Would a #4 filter paper for silver chloride and silver powder filtration then a #5 for any gold solution/precipitate filtration suffice? 

Sent from my SM-G920F using Tapatalk


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## Tndavid (May 6, 2017)

autumnwillow said:


> Would a #4 filter paper for silver chloride and silver powder filtration then a #5 for any gold solution/precipitate filtration suffice?
> 
> Sent from my SM-G920F using Tapatalk


I think I've seen that combo used willow. But then again if the solution is still not Crystal clear there will still be contaminates. I'm still poor as far as equipment goes and still use coffee filters. Yea I know guys. But anyways I filter until the contaminates fill the pores in the filter paper and then I'll continue filtering until my AuCl is clear. Even with coffee filters via a lot of filtering you can still get a really pure product. The clarity of your solution will tell you a whole lot.


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## autumnwillow (May 6, 2017)

Just noticed that silver chlorides bypasses a #1 filter. Proceeding with a #4 filter will not be good. I think a #5 will be enough for aucl. We used to use a #42 and a #2. This #1 whatman filter is the worse filter that I have used. Very slow, clogs easily and some precipitate bypasses the filter. 

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## anachronism (May 6, 2017)

A number 1 to filter solutions with silver chloride in is fine if used correctly. It certainly won't block the filters, in fact I use these filters for volumes of silver chloride precipitated from silver nitrate using HCl. The only think I have found that blocks a number 1 filter is fines from ashed carbon. 

I agree that sometimes I have had to filter twice though, often using the same original filter.


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## autumnwillow (May 7, 2017)

Is there a way to keep the agcl precipitate above 25 micron size? Perhaps using a different precipitant? Temperature control? Diluting the solution further or vice versa? 

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