Gold Refining Karat Scrap Complete Process - VIDEO

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Thank You. I noticed several techniques you do differently that I will be adopting soon as I get back to refining.
 
Excellent, Kevin!

I do have a couple of things, though.

(1) Ice vs dilution to drop AgCl. I've always felt that the ice method isn't nearly as efficient and I think you proved this in your video. I noticed that, when adding the ice to the 2nd AR, you still got a lot of AgCl dropping. Had you diluted the AR with 3 times water (instead of using the ice), in the 1st AR, you would have had no AgCl dropping in the 2nd AR, since it was all filtered out the 1st time.

Ice would drop most of the AgCl but, if the solution is allowed to warm, at all, even a few degrees, before it all goes through the filter, it will tend to re-dissolve (re-stabilize itself). Then, any rinsing dilutes the solution and causes the AgCl to re-precipitate, thereby contaminating the gold. Think about it. Before filtering, if the chilled solution is allowed to warm, you are essentially back to square one.

If you do use ice, I would use enough to get it down to about 33F and hold it there for awhile, Use the vac filter so it will suck through fast. It could help to freeze the funnel beforehand if it's made of porcelain.

Also, 3X dilution tends to take the power out of HNO3 that is present. Had you diluted and filtered the 1st AR, I would bet that the ferrous sulfate drop would have been trouble free. There are limits to this, of course.

(2) What's this about a brown stain when testing Au with stannous chloride? I've been doing this all my life and, when Au was present, the color always ranged from light purple to a very dark purple (essentially black), depending on the Au content - never brown, never, not with Au. The problem with brown is that other metals can also give brown. I think people call this a false positive although I never understood why - it's either purple or it isn't. I should mention that, while working with AR, I usually made up a fresh solution of stannous chloride, first thing, each morning - 1g stannous chloride, 15ml HCl, 15ml water - took only a couple of minutes to make it. I bought a 1/4 pound (113g) of stannous chloride crystals on eBay for about $11. I think the ad is still there but the guy went up a couple of $'s. I've never used tin solder to make it and maybe that could be the difference. When you tested the stannous chloride with the known gold solution, the color didn't look right to me.
 
goldsilverpro said:
Excellent, Kevin!

I do have a couple of things, though.

(1) Ice vs dilution to drop AgCl. I've always felt that the ice method isn't nearly as efficient and I think you proved this in your video. I noticed that, when adding the ice to the 2nd AR, you still got a lot of AgCl dropping. Had you diluted the AR with 3 times water (instead of using the ice), in the 1st AR, you would have had no AgCl dropping in the 2nd AR, since it was all filtered out the 1st time.

Ice would drop most of the AgCl but, if the solution is allowed to warm, at all, even a few degrees, before it all goes through the filter, it will tend to re-dissolve (re-stabilize itself). Then, any rinsing dilutes the solution and causes the AgCl to re-precipitate, thereby contaminating the gold. Think about it. Before filtering, if the chilled solution is allowed to warm, you are essentially back to square one.

If you do use ice, I would use enough to get it down to about 33F and hold it there for awhile, Use the vac filter so it will suck through fast. It could help to freeze the funnel beforehand if it's made of porcelain.

Also, 3X dilution tends to take the power out of HNO3 that is present. Had you diluted and filtered the 1st AR, I would bet that the ferrous sulfate drop would have been trouble free. There are limits to this, of course.

(2) What's this about a brown stain when testing Au with stannous chloride? I've been doing this all my life and, when Au was present, the color always ranged from light purple to a very dark purple (essentially black), depending on the Au content - never brown, never, not with Au. The problem with brown is that other metals can also give brown. I think people call this a false positive although I never understood why - it's either purple or it isn't. I should mention that, while working with AR, I usually made up a fresh solution of stannous chloride, first thing, each morning - 1g stannous chloride, 15ml HCl, 15ml water - took only a couple of minutes to make it. I bought a 1/4 pound (113g) of stannous chloride crystals on eBay for about $11. I think the ad is still there but the guy went up a couple of $'s. I've never used tin solder to make it and maybe that could be the difference. When you tested the stannous chloride with the known gold solution, the color didn't look right to me.
Click to expand...

Even chilling the funnel down will not keep the solution temperature down long enough the way he is doing it.

The way he is using his ferrous sulfate with that particular brand it needs to be dissolved in water with some HCL as he is doing it and allowed to set over night then filtered without disturbing the sediment that drops.The solution once filtered and all sediment removed it can be stored in a plastic jug for periods of time and work fine.

I would be a more precise in the use of the SMB you are using. Since you have an approximate weight of the gold you are recovering you can weigh out your SMB and dissolve it in water then add it to your solution. Rather than just dumping spoon fulls of SMB into your solution. I would have to say that the color from the stannous test was from the use of so much SMB.

Over all I would say a good production on the video.
 
I have never used 3x water dilution for silver chloride removal. I must try this on my next refining. I have just recently started using copperas for the first precipitation. I did have some copperas already dissolved, Hydrochloric acid added and completely settled on hand as barren realms pointed out. But wanted to demonstrate how to prepare the copperas solution for the video.

Thanks for these tips! I enjoy refining my refining process. Just goes to show that I am still just an advanced beginner.

By the way, I have used this double refining method demonstrated in this video at least a dozen times and the assay always comes back three nines without fail.

Thanks,
kadriver
 
goldsilverpro said:
Excellent, Kevin!

I do have a couple of things, though.

(2) What's this about a brown stain when testing Au with stannous chloride? I've been doing this all my life and, when Au was present, the color always ranged from light purple to a very dark purple (essentially black), depending on the Au content - never brown, never, not with Au. The problem with brown is that other metals can also give brown. I think people call this a false positive although I never understood why - it's either purple or it isn't. I should mention that, while working with AR, I usually made up a fresh solution of stannous chloride, first thing, each morning - 1g stannous chloride, 15ml HCl, 15ml water - took only a couple of minutes to make it. I bought a 1/4 pound (113g) of stannous chloride crystals on eBay for about $11. I think the ad is still there but the guy went up a couple of $'s. I've never used tin solder to make it and maybe that could be the difference. When you tested the stannous chloride with the known gold solution, the color didn't look right to me.
Click to expand...

The stain looks brown as soon as I apply the stannous, but if set aside a few minutes on a clean paper towel as I do with all the tests stips I use, then the color always turns purple.

I am using Stannous with pure tin shot and stannous chloride crystals and HCl in a little distilled water. I add a few drops of HCl to freshen it up from time to time, if there is still some tin shot in the bottom.

I like the idea of using freshly prepared stannous as you suggested. Thanks for your input. These critical comments are the reason I post, so that I can learn more and become a better refiner.

kadriver
 
Two questions. Are you using a hcl wash after the 2nd drop? Are you using two filter papers in the buchner?
 
Barren Realms 007 said:
I would be a more precise in the use of the SMB you are using. Since you have an approximate weight of the gold you are recovering you can weigh out your SMB and dissolve it in water then add it to your solution. Rather than just dumping spoon fulls of SMB into your solution. I would have to say that the color from the stannous test was from the use of so much SMB.

Over all I would say a good production on the video.
Click to expand...

Barren,

I'm not a chemist in any sense, I wouldn't know the "P" block from the "S" block except for watching a few videos on Khan Academy. How would one go about calculating the amount of SMB to use if the approximate quantity of pure gold yield is known?

Can you show an example please?

Thanks
kadriver
 
Palladium said:
Two questions. Are you using a hcl wash after the 2nd drop? Are you using two filter papers in the buchner?
Click to expand...

I use a few ml of HCl to rinse the gold powder while its in the funnel just before I add it to the melt dish.

I am using a single filter paper in the Büchner funnel, rated "slow" out of fast, medium and slow.

I have'nt had much luck using two filter papers In a Büchner funnel. One always seems to float while I pour the liquid into the funnel.

kadriver
 
The silver chloride carries over from your drop. Two filter papers will help reduce that for the solids. I notice all you do is rinse the gold after inquarting. Remember that gold is honeycombed and by just swirling water over it you're not going to wash it clean. You need to boil it for a few minutes as a last step. This is where the break down starts. When you dissolve it in ar you think you don't have any agcl, but a certain amount is soluble in the ar that carried over from the poor washing. Then once you go to precipitate the gold from what you think is a clean solution the agcl forms as a collide and starts to drop first before the gold. This is a seed crystal much like a snow flak starts. As the nucleation of the gold starts it uses the agcl as it's seed crystal. The gold particles start to form around the seed and builds in mass to what you see in size as your gold precipitant. Then you do a 2nd dissolve thinking you got the agcl. Nope a certain amount is soluble so it went back into solution. You drop it again thinking it's gone but it is not. Theirs always this minute amount that wants to hang around. The dilutions force it out. Gold filled is a pain in the *** for this type of contaminate. Here again just washing with a diluted solution of hcl and water washes will not reach the center of the formation. When you do the hcl wash use your hcl straight and boil it for a few minutes. Your not going to hurt it. Then the same with a water wash. Most times if you don't get it it will be gotten in the burn off in the dish if it's not much, but have you ever wondered what that skim was floating around on top of your gold and flux that you knew just shouldn't be there? Water is better like Chris said. I use water dilution. Harold always used an hcl wash even after the ice bath. That's why he caught his. The agcl that carried over in the drops and was finally separated from the gold in the hcl wash and carried away in the waste wash. Then you get pure shiny gold like the thread shows. Not saying that either way is right or wrong, it's just geared to the refiners liking and skill sets. As long as the end result is the same that's what counts. The only time i have a paper float is when you pull the vacuum off with liquid in the funnel or the vacuum is weak. Put two paper in and wet them. Then apply vacuum. Once the paper is seated don't take the vacuum off until the filter is empty and the paper has sucked dry and reseated itself.

Great video! I like the way you demonstrate things!
 
To avoid adding too much nitric I add less than the calculated amount at the beginning, then when I have dissolved most gold, approximately 90%, I let the reaction go to completion and pour off the gold chloride. Then I add a bit more HCl and small amounts of nitric. As the volume is smaller and the acids stronger it's easier to dissolve the last part without adding too much nitric.

Nice video, I have never used ferrous sulfate so the dark barren solution was a surprise to me.

The washing in the filter was also a first for me, I would expect it to be hard to wash out some contaminants as the acid would drain through the path of least resistance. If the powder is boiled in the beaker it could easier penetrate clumps of gold powder and dissolve more stubborn contaminants over longer time.
For me the powder stays in the same beaker from filtering the gold chloride, thru precipitating, washing and drying.
... but that is my way to do it, and there are many ways to refine gold. 8)

The rule of thumb for SMB is one gram dry SMB drops one gram of gold. I've read that on the forum.

Göran
 
kadriver said:
Barren Realms 007 said:
I would be a more precise in the use of the SMB you are using. Since you have an approximate weight of the gold you are recovering you can weigh out your SMB and dissolve it in water then add it to your solution. Rather than just dumping spoon fulls of SMB into your solution. I would have to say that the color from the stannous test was from the use of so much SMB.

Over all I would say a good production on the video.
Click to expand...

Barren,

I'm not a chemist in any sense, I wouldn't know the "P" block from the "S" block except for watching a few videos on Khan Academy. How would one go about calculating the amount of SMB to use if the approximate quantity of pure gold yield is known?

Can you show an example please?

Thanks
kadriver
Click to expand...

That is not a problem. For each gram of gold you calculate recovering I use 1g of SMB. I also add more ice to the solution when I am ready to make my drop.
 
Palladium, your explanation on HCl wash is excellent. I can see the evidence of the AgCl all the way through my process like you and Chris point out.

I can see Chris' point; even though the filtrate is crystal clear, the chloroauric acid has heated back up which would hide any cloudiness that chilling would reveal.

One thing I didn't show in the video was this;

Just before pouring, I got the molten gold real hot, then added a tiny pinch of potassium nitrate.

The gold never has a skin, the surface of the poured gold is contamination free, and the gold always assays nothing less than three nines.

I am not seeing a need for the additional HCl washes based on the appearance of the final gold, and the assay. You don't suppose that the refiner that I am selling to is gun decking the assay? Would'nt the silver chloride report as silver contamination in the assay?

On my next refining I'll put the final filtering in the refrigerator for a few hours to see if any AgCl cloudiness forms just before I precipitate.

After that I want to try the 3x water dilution - would that be 3x distilled water, or 3x tap water?

Thank you for taking the time to give this excellent feedback.

kadriver
 
Kevin,

Tap water is fine for dilution. I've used tap water from many different cities and never once had a problem. I use tap water in all cases except when silver is dissolved in nitric. With gold, I would only consider distilled when the tap water is cloudy and/or, not colorless.

The only disadvantage of 3X dilution I can think of is that there is more waste solution. However, the advantages of dilution greatly outweigh this, in my experience - Easier drops - Silver (as chloride) almost totally eliminated at the 1st filtering.

In the 60's, I determined how much silver was removed by dilution. I added some AgCL to a strong AR solution, stirred it, let it sit and settle for quite awhile, and then analyzed the silver in the clear solution using an AA. I added enough water to the same solution to make up a 1:1 dilution and analyzed it. I then added water for 2X, 3X, 4X, and 5X dilutions, in order, and analyzed each sample. I'm thinking that about 85-90% of the silver was gone after 2X and about 98-99% after 3X. Diluting 4X only improved it a tiny bit and 5X did hardly anything at all. That's why I settled on 3X.
 
Or just rinse the silver chloride out with strong HCl to complex the silver and any copper.

Nice thing about the ammonia water rinse is you can see any copper go, but that copper is only going to go if it's copper (II), not copper (I) which is what most of the copper contaminant is. Use strong HCl and you get the copper and the silver removed.

I wrote a post about that rinse somewhere...
 
goldsilverpro said:
Kevin,

The only disadvantage of 3X dilution I can think of is that there is more waste solution. However, the advantages of dilution greatly outweigh this, in my experience - Easier drops - Silver (as chloride) almost totally eliminated at the 1st filtering.
Click to expand...

How could I have over looked this for so long? This is like the silver chloride holy grail. I just don't remember ever reading about it here on the forum. Thank you for sharing!

I have more experiments to do now to verify a few things. I'll refigerate the final filtering after using ice to chill, as per the video to see if the AgCl will precipitate upon cooling.

I also will do an HCl boil and boiling water rinse as described by Palladium for comparison.

What was the "AA" that you used to analyze the silver chloride content?

This is like attending graduate level refining college!

kadriver
 
g_axelsson said:
To avoid adding too much nitric I add less than the calculated amount at the beginning, then when I have dissolved most gold, approximately 90%, I let the reaction go to completion and pour off the gold chloride. Then I add a bit more HCl and small amounts of nitric. As the volume is smaller and the acids stronger it's easier to dissolve the last part without adding too much nitric.

Göran
Click to expand...

This has crossed my mind from time to time. It seems like a valid process (I use this when doing silver). I'm going to try it.

Another point; adding too little HCl can cause a problem. I was doing a batch a while back and kept adding nitric but the gold would not dissolve. Then I added a pipette full of HCl and the reaction took off. I think this may have happened in the video and that is why I have excess nitric in the chloroauric acid solution for the copperas precipitation.

Thanks Goran
kadriver
 
Lou said:
Or just rinse the silver chloride out with strong HCl to complex the silver and any copper.

Nice thing about the ammonia water rinse is you can see any copper go, but that copper is only going to go if it's copper (II), not copper (I) which is what most of the copper contaminant is. Use strong HCl and you get the copper and the silver removed.

I wrote a post about that rinse somewhere...
Click to expand...

We don't want to crush the pieces of gold, we want to leave them just as they are for the HCl wash - correct?

kadriver
 

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