REDUCTION OF GOLD

[eaglewings35]

No need to add water. You just boil off a bunch of acid.

So, by simply boiling off the acid, the gold will precipitate out?
Thats amazing !!!
At what point will the acid crystalize? Should I just do barely a rolling boil?
I plan on putting some coffee filters on top of my jar, secured by a rubberband.
Hopefully this will catch any values that may be lost due to boiling, and I can test the filters later for gold.

Still, I ask, if there are any other metals, like silver, platinum, ect. that are dissolved in the solution too, how will the boiling off the acid affect them? Will you be able to see them?
Can they be separated out at that point, or will they be bonded still with the gold?

Thanks

 

[Topher_osAUrus]

Dont boil!
Evaporate slowly.

Any silver in solution would be a pain, as its in chloride form and evaporating the moisture would dry it out. And as Lou pointed out earlier in the thread, dry silver chloride doesn't have very many options to put it in solution, or get it back to metallic form.

This would probably be best if done with a relatively pure gold solution..

Harold spoke of, many times, when he evaporated his gold solutions down metallic gold would begin to precipitate.

I think I'll stick to standard precipitation methods.. Using sodium metabisulfite is about as easy as it gets.

 

[aga]

At what point will the acid crystalize? Should I just do barely a rolling boil?

The AR acids won't ever crystallise by heating, they'll volatilise and drift out of the pot into the air.

Dont boil! Evaporate slowly.

Lou clearly knows his stuff and probably uses 'boil' as a shorthand way to say 'evaporate at an appropriate temperature' ( = a lot less typing !)

One of the problems with simple boiling is the splashing, which throws some of your gold-containing liquid away.

Another problem is how fast the acid vapours are being made - you need to make sure you can get rid of them fast enough to stay safe (alive even).

When the liquid is around 40 C, you will see vapours coming off (including water), slowly.

At 90 C it happens a lot faster, but is not boiling.
Adding a small fan to remove the vapours makes it quicker too.

A possible problem with trying to go faster is 'mechanical entrainment' where the water/acids leave so fast that they take a small amount of your gold compounds with them. Never seen any science showing the actual amounts lost, so no idea if this actually happens to any appreciable extent.

In the end, it's a balance between how much gold you want versus how long you want to wait.

Certainly best to follow the advice given on this site if you're not 100% sure what to do.

Edit:
Clarified which acids won't crystallise by boiling.

 

[eaglewings35]

Thank you for the very fast replies.
Yes, Lou is one of my favorites on this forum. You can tell from his writing,
he has a great deal of knowledge, smart guy-Ah?
I do have some very clean and clear gold solution... I have nothing but time, I think I will
give it a try.
Do you think the added security of putting a few filters on the mouth of my jar, is a good idea?
This way I can capture any gold that may have gotten out during the EVAPORATING (not boiling) process.

Thanks

 

[aga]

Evaporate slow enough and you'll not lose much.

If you add a filter paper on top, it will evaporate slower, then you'll want to process the filter paper too ...

Up to you to choose between getting 99% of All the gold in 100 years, or lose some and get 90% of the gold a lot sooner.

 

[Lou]

Aga, you are right on my boiling comment and I thank you for clarification. Topher, you are right too.

I will go into more detail and address some things:

1. I said "boil" because in the right apparatus, you can boil solutions and experience negligible loss, but it is probably best to evaporate first, and then strongly heat the slush of gold crystals to disproportionate the HAuCl4 into gold and gaseous products (which pushes the reaction forward). Note that an excess of chlorine will be required for the gold to transport any significant distance.

Generally speaking...do NOT boil solutions. Sure, it makes aqua regia go faster on silver items because the nucleation of bubbles on the dissolving material de-scales the AgCl but the downside is that money is surely lost from open beakers!

Boiling a solution does cause mechanical entrainment of values. A tall container is indicated.


2. Other metals will form firstly their chlorides, then their oxides with strong continued heating. The exceptions are the noble metals, sans silver, all of which are noble because they generally prefer not to exist as oxides. Platinum will contaminate gold, so too will Pd if these solutions are evaporated to dryness.

If you read above, you will see I mentioned a common procedure. It is called fuming with sulfuric acid. Metal sulfates are generally (except for silver and a few other oddballs) more stable to heat than chlorides, at least in air. The sulfuric basically distills off all of the HCl as a gas and leaves you with your impurities (including silver but excluding lead, barium, and a few oddballs), as soluble compounds and the gold as metallic gold.

Analytically, you can retard this decomposition phenomenon by the addition of sodium chloride.

 

[4metals]

Lou clearly knows his stuff and probably uses 'boil' as a shorthand way to say 'evaporate at an appropriate temperature' ( = a lot less typing !)

Exactly and Amen!

There are many respected authors of technical manuals that use the term boil, yet if it is mentioned here it is a sacrilege worth of stoning. Common sense has to apply to refining or any chemical processing or as one member's signature line puts it, you can't fix stupid!

 

[Topher_osAUrus]

:lol: :lol:

Well, it's like mentioning the safety stuff repeatedly..
The majority here, already know to not taste acids, and wear gloves, and use proper sense...

But, this is the internet...where common sense is far from common.

So, some new guy may see boil, and proceed to crank it up! -more power! ...Then wonder why he only has a couple grams left of his ounce.

...it is sooo much easier to say boil than "slowly evaporate" though.

 

[aga]

it is sooo much easier to say boil than "slowly evaporate"

It is, so all we need to do is define a GRF meaning for 'Boil', a bit like the Oxford Dictionary does, then cite that definition if anyone gets confusled.

Normal 'Boil' :
"Heat the thing like mad until it hubbles and bubbles like crazy, steaming and throwing stuff everywhere"

GRF 'Boil':
Suggestions anyone ?
(too ashamed to make my own before i got even a tiny blob of gold to show for my efforts )

 

[Grelko]

GRF 'Boil':
Suggestions anyone ?

Evanish or fade 8)

http://www.thesaurus.com/browse/evaporate

 

[g_axelsson]

We don't need any new definition for boiling, it would only change that we need to write evaporate when we mean evaporate instead of writing boil and then go on and explain that it doesn't mean boil but evaporate.

What we need is just to take those five extra characters to write evaporate and if we makes a mistake, someone will catch it.

... and redefining boil we need another word for boiling. I suggest we use freeze.
In other words, you have to boil your solution and not freeze it or you will lose some gold. :mrgreen:

This statement is a statement released by the institute of redundancy institute and is written in newspeek.

Göran

 

[upcyclist]

Or we could just add 'boil' to the forum's profanity filter :lol: