# Inquartation with sulfuric acid



## ElectricAngel (Oct 17, 2012)

As we all know, nitric is hard to get in the USA, and expensive to boot. (I wonder if Canada offers me any respite? I'm going there soon, and could make a trip to a supply store if there is any hope of $1 a litre niric.)

Anyway, I read Hoke. She mentions that it is possible to treat inquarted gold with sulfuric instead of nitric acid. From about page 64, we read:
"When very large lots, running 100 ounces and over, are treated, sulphuric acid may be chosen; but it is suitable only when the added metal is silver, when the copper content of the resulting button is 10% or less, and when the lead content is low. Sulphuric acid is cheaper than nitric, but more unpleasant to handle. Since your purpose at this time is to learn the various modifications of these processes, we suggest that you now take a button in which silver is the added metal, which con-tains little or no lead, and in which copper runs not over 10%, and treat it with sulphuric acid instead of nitric acid."

Intriguingly, she adds: "Returning now to the gold in the porcelain dish: wash it well,to remove all sulphates of copper or silver. As we said before, this gold may be as pure as you require. The exact purity will depend mainly upon the nature of the metal you started with, partly on your skill and patience, and partly on the composition of the button you obtained by inquartation. Thus, if the gold in your button is too high, say 30% or so, the gold you recover will be of doubtful purity. (That is why some workers make up their buttons with a gold content of only 10% or 15%, although this means added ex-pense in acid and time, and rarely pays.)"

SO, has anyone here followed Hoke and inquarted gold with pure silver, and then used sulfuric to generate gold of high purity? 

I read another post where two inquartations (using nitric on the first) were suggested: the second was to inquart the gold with zinc, and then digest the zinc with HCl, leaving behind .999 gold. But zinc boils at a temperature below where gold melts, so I have no idea how one would inquart nearly-pure gold with zinc.


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## butcher (Oct 17, 2012)

Hot concentrated sulfuric is extremely dangerous, and is not recommended by the forum, if you got this solution spilled on you from broken glassware or some other accident it can burn you almost to the bone:

http://www.google.com/search?num=10&hl=en&site=imghp&tbm=isch&source=hp&biw=1024&bih=503&q=sulfuric+acid+burns&oq=sulfuric+acid+burns&gs_l=img.3..0j0i24l3.1719.10828.0.11750.19.13.0.6.6.0.344.3609.2-10j3.13.0...0.0...1ac.1.PQHNcHwo6mE

As all of us who work with these chemicals know an accident will happen when you least expect it, and they will happen.


Concentrated sulfuric will dissolve silver and gold, gold will precipitate when solution is diluted, salt could be added to form silver chloride and HCl in the dilute solution to precipitate silver.

Even diluting the solution can be extremely dangerous,

Never add water to concentrated sulfuric acid, as soon as water touches it explodes into steam splashing the concentrated acid all over the place as the water expands into steam so fast, and increases tremendously in volume, it is like an explosion of concentrated acid.

Always dilute by carefully pouring acid into water.

Using the concentrated acid to part gold and silver is not a good idea.

It is just too dangerous.

Nitric can be hard to get, and can be expensive, it is not a safe chemical but it can be worked with if done safely.

With the sulfuric you may not get a second chance if crippled for life.

Would a few grams of gold be worth it?

Nitric acid can be made in your lab and distilled, in the USA it can usually be purchased.

Why take a risk with your safety.


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## nickvc (Oct 17, 2012)

I'm in full agreement with Butcher on this, hot concentrated sulphuric is second on my acids to avoid list after hydrofluoric.
Depending on what you are aiming to refine there are ways round the use of nitric but it might take a little extra work. Many karat alloys are low in silver so perhaps melting the material and making cornflakes and then dissolving them in heated poor mans AR, add a few drops of sulphuric, cool then filter and precipitate. This will give you a dirty powder so use Harold's rinsing technique and then redissolve the powder using hydrochloric and bleach, which works well on powders and foils, heat your solution to drive off the chlorine and again cool, filter and precipitate. I will admit I have never used poor mans so I'm guessing it would work, I'm sure someone here knows, but I have regulary dissolved karat scrap directly in AR and it works well so long as the silver content is low, any pieces left after the digestion is just added to the next batch for melting.


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## butcher (Oct 17, 2012)

would take longer than aqua regia made with acids but it will work, but if too much silver could cause trouble.

Adding copper instead of silver to the karat gold would make it easier to part in poormans nitric acid.

making and distilling nitric acid is not that hard, there are some important things to learn, but once you understand how to do it safely it is no big deal.


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## nickvc (Oct 17, 2012)

Butcher I was thinking to melt the karat scrap as is so long as its low in silver content, many modern alloys are very low to zero silver content, as i stated I frequently do this with AR, but the downside is it will be a dirty precipitate hence the thought of using the chlorox process to clean it on the second refine, poormans to recover, chlorox to refine. It's a sort of work around when nitric is hard to impossible for members to get or produce at home, that's if it works i have have never used poormans so I'm not sure. I know the AR works and if done right will produce excellent results but it takes experience to achieve high purity with one shot and wouldn't advise the method to most. A point I did forget to stress is to test all solutions with stannous after precipitation....just in case!


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## Irons2 (Oct 17, 2012)

Zinc will boil away if one tries to melt it with Gold. Hoke mentions the use of Brass. I have found that it works quite well. I use old cartridge cases that are high in Copper. Brasses melt between 900 and 950*C, so it works well as far as melting points go. The Zinc will boil off if the alloy gets really hot, and you can see the bubbles forming in the flux when that happens, it will also boil off if you cool it slowly, just before hardening, as the Zinc separates out of the Alloy. If you pour it into Water to cornflake it in preparation for dissolution, it forms a very nice homogenous alloy.

This is not recommended with feedstock that contain PGMs, as they will not go into solution as they do with Silver, then parting with Nitric. Native Gold almost always contains some Platinum Group Metals, so Silver and Nitric is the way to go in that case.

From an economic standpoint, I would rather lose Copper and Zinc into the Flux than Silver, even just to eliminate having to process the flux to recover Silver.


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## ericrm (Oct 17, 2012)

ElectricAngel said:


> As we all know, nitric is hard to get in the USA, and expensive to boot. (I wonder if Canada offers me any respite? I'm going there soon, and could make a trip to a supply store if there is any hope of $1 a litre niric.)


 :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: 

good luck with canada...


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## ElectricAngel (Oct 17, 2012)

butcher said:


> Hot concentrated sulfuric is extremely dangerous


Heck, even the rather dilute stuff I've used in electrorefining has ruined some of my clothes with just a tiny splash. Fortunately, I now have a set of ruined clothes I can wear when working with sulfuric acid. I am aware of the dangers of these acids, even outgassing from HCl. The time to worry is after I have done this for a while and become nonchalant. 



butcher said:


> Concentrated sulfuric will dissolve silver and gold, gold will precipitate when solution is diluted, salt could be added to form silver chloride and HCl in the dilute solution to precipitate silver.


I guess this is my confusion, then. I gather from what you wrote that the acid needs to be heated, not a pleasant prospect, but everything I ever read told me that only AR would dissolve gold. I was hoping that the concentrated acid would only eat the silver and copper (I'd inquart with some scrap sterling) and leave behind mostly pure gold; I'd then recover my silver with HCl and process the silver chloride separately. (Would using HCl regenerate the sulfuric acid in the dilute? Then I could reuse my sulfuric, which is cheaper than nitric, but not cheap.)



butcher said:


> Never add water to concentrated sulfuric acid, as soon as water touches it explodes into steam splashing the concentrated acid all over the place as the water expands into steam so fast, and increases tremendously in volume, it is like an explosion of concentrated acid.


Yes, Hoke makes certain to repeat that warning EVERY TIME. I have internalized it.



butcher said:


> Would a few grams of gold be worth it?


I generally don't like the acid methods, so, no. I am trying to get electrorefining for Au, Ag, and Cu going correctly. The eventual target with any mostly-pure buttons that result from the 99+% pure residue of inquartation is gold electrorefining.



butcher said:


> Nitric acid can be made in your lab and distilled, in the USA it can usually be purchased.


I did the cold distill, single-cup method using NaNO3 and H2SO4; the yield is not high, and the cost immense, but it gave me some Nitric to experiment with, which is what I had wanted. When I have used NaNO3 and HCl to digest gold, I have done so under a glass dome that forces the NO2 into a solution of water and H2O2, which regenerates a (very weak) Nitric, but that weak nitric was of essentially no use to me.



butcher said:


> Why take a risk with your safety.


I appreciate Hoke and this board especially for these cautions. These are not chemicals to play with or to treat without respect.


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## ElectricAngel (Oct 17, 2012)

Irons2 said:


> Zinc will boil away if one tries to melt it with Gold. Hoke mentions the use of Brass. I have found that it works quite well. I use old cartridge cases that are high in Copper. Brasses melt between 900 and 950*C, so it works well as far as melting points go. The Zinc will boil off if the alloy gets really hot, and you can see the bubbles forming in the flux when that happens, it will also boil off if you cool it slowly, just before hardening, as the Zinc separates out of the Alloy. If you pour it into Water to cornflake it in preparation for dissolution, it forms a very nice homogenous alloy.



Thanks, Irons2. I had come across the following: http://goldrefiningforum.com/phpBB3...3701&hilit=inquartation+sulfuric+zinc#p113701 where someone mentioned inquarting gold with zinc, but I cannot see how it would be done. I have to assume it cannot.


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## ElectricAngel (Oct 17, 2012)

ericrm said:


> :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol:
> 
> good luck with canada...


Are they even worse than the USA? I have no idea. 

I do know that "corrupt, backward" Mexico is substantially freer in this regard. It's disheartening to read Hoke with her discussions of common chemicals available in 1940 and recognize that I live on the same land she did, but a different country.


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## Irons2 (Oct 17, 2012)

ElectricAngel said:


> Irons2 said:
> 
> 
> > Zinc will boil away if one tries to melt it with Gold. Hoke mentions the use of Brass. I have found that it works quite well. I use old cartridge cases that are high in Copper. Brasses melt between 900 and 950*C, so it works well as far as melting points go. The Zinc will boil off if the alloy gets really hot, and you can see the bubbles forming in the flux when that happens, it will also boil off if you cool it slowly, just before hardening, as the Zinc separates out of the Alloy. If you pour it into Water to cornflake it in preparation for dissolution, it forms a very nice homogenous alloy.
> ...



Brass is an Alloy of Copper and Zinc. The Copper keeps the Zinc from boiling off.


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## etack (Oct 17, 2012)

As a thought what if you were to melt you Karat scrap with tin. If you made it 25% gold and the rest with tin wouldn't you be able to "dissolve" you gold in melted tin like hot solder or mercury dose? This way all you would have to do is use HCl. gather you gold and use HCl/bleach

his is just outside the box thinking not a recommendation as of yet.

Thoughts anyone. Its not dangerous but it puts tin in you equation. I nitric is not used that that should be OK right?

Eric


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## Geo (Oct 17, 2012)

i believe the gold would have to be either very thin or very finely divided like powder, otherwise the tin would just boil away before the gold started to melt. you may be able to melt the gold first and then add the tin with a flux, maybe.


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## etack (Oct 17, 2012)

my thought was if you had a pot of molten tin like melting lead then added your gold to it and letting it dissolve in the tin. This would take more time but it might be cheaper for some.

Eric


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## ElectricAngel (Oct 17, 2012)

Irons2 said:


> Brass is an Alloy of Copper and Zinc. The Copper keeps the Zinc from boiling off.



Which leads to another "infinite recursion" question. Copper melts at a temperature higher than zinc boils, and yet I know that brass exists, so there must be a way to make an alloy of them. 

Just did a little research. It seems that if you add solid zinc to molten copper, some of the zinc will boil off, but the rest will form a brass. I wonder if the same is possible with gold?

This has now entered the territory of "too hard."


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## etack (Oct 17, 2012)

Zinc fumes are no fun research that first. FYI

Eric


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## Irons2 (Oct 17, 2012)

ElectricAngel said:


> Irons2 said:
> 
> 
> > Brass is an Alloy of Copper and Zinc. The Copper keeps the Zinc from boiling off.
> ...


The ancient Romans had making Brass down to an Art. They used a ceramic pot with 2 chambers. One contained granulated Copper, the other, Zinc. When the pot was heated, the Zinc would boil and be Amalgamated into the hot Copper grains, much like Mercury would.. back then, Brass was quite the novelty and considered valuable. It seems that trade secrets can last a long time. :mrgreen:


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## HAuCl4 (Oct 18, 2012)

Irons2 said:


> ElectricAngel said:
> 
> 
> > Irons2 said:
> ...


Copper and gold have about the same melting point... the rest of the story you can imagine it... white golds used to be made from an alloy of nickel, zinc, and cadmium... fumes everywhere or not, depending on the craftman doing the work. :lol:

If I had to guess, I'd say that more than half of the gold in reserve vaults before 1950 had been obtained by inquartation and parting with sulfuric acid in cast iron pots and has a fineness of about 997. :shock:


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## pugle1 (Oct 23, 2012)

ElectricAngel said:


> ericrm said:
> 
> 
> > :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol:
> ...




Even sodium nitrate or ANY nitrate (ammonium, potassium etc) for that matter is hard to get here in Canada.... they're now controlled substances (stupid terrorists). I was pricing nitric acid here, and yup.... seems the best price I could find was somewhere near $230 Cdn for 500 ml of 70% (Alphachem or Kencro). There are wide price ranges however... I guess nitric could be had if one were to shop around. One site was listing it as high as $1300 + per liter.


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## Irons2 (Oct 23, 2012)

Make a Law, make a Business.


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## pugle1 (Oct 27, 2012)

This is a copy of a PM sent to ElectricAngel regarding Nitric prices in Canada.... some of our Canadian refiners might find it useful....


I contacted AlphaChem in Mississauga, Ontario.

These are the prices as quoted to me:

Hydrochloric ASC - 4 liter - $28.00 Cdn
Nitric Acid 69.0% - 70% ASC - 500 ml - $31.50 Cdn (Min 1 bottle but sold in six bottle cases)
Sulfuric Acid ASC S/S - 500 ml - $41.60

Try http://www.alphachem.ca - there is a "contact us" link there as well.

Hope that helps 

Regards,

Paul


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## skippy (Feb 7, 2013)

I tried dissolving some silver with sulfuric acid in a small flask ported with a tube to a scrubber (A bubbler would be a bad idea in case of suck back - it would be a very dangerous, deadly, in fact the whole process has extreme potential for danger). The reaction started ok, but slowed down drastically before much silver was dissolved. On some thinking I figured it must be that the reaction was producing water which was killing the reaction by diluting the sulfuric. I did some more reading, and when this method was state of the art the process was done in big iron stills that were entirely kept at a very hot temperature to drive off any water formed and could also port off the SO2 for treatment. The only way I can see around using a fancy apparatus like this would be to use a open beaker which would allow the water to disipate. This seems like too much to subject a fume hood to unless it's small scale. Dunno though. It's an interesting method, which made sense back then because nitric was expensive before they figured out how to synthesize nitric acid from nitrogen. It would be nice if there was an easy way to make it work but I can't see it.


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