Washing process and no ice available.

[autumnwillow]

I'm pretty sure hoke's method is a bit outdated. And I've been trying to search the forum for hours now and could not find an answer.

1) How do you wash your fine gold from AR precipitated with SMB?
Hot water 3x,
Boil to concentrated HCL
Hot water 3x
Ammonia ? boil? or what?
Hot water 3x
Dry. Melt with small amounts of borax.
Anything I've missed here?

I will be using sulfamic acid to neutralize the acid.

2) I don't have ice available. Can I just put the beaker in a cold stainless steel bowl?

 

[Topher_osAUrus]

I'm pretty sure hoke's method is a bit outdated. And I've been trying to search the forum for hours now and could not find an answer.

1) How do you wash your fine gold from AR precipitated with SMB?
Hot water 3x,
Boil to concentrated HCL
Hot water 3x
Ammonia ? boil? or what?
Hot water 3x
Dry. Melt with small amounts of borax.
Anything I've missed here?

I will be using sulfamic acid to neutralize the acid.

2) I don't have ice available. Can I just put the beaker in a cold stainless steel bowl?

Hot water yes
Hcl yes
Water yes
Ammonia-some do, some dont....some do dilute sulfuric instead
Hot water yes

When in this process are you needing ice?

It should be BEFORE you precipitate with smb, to dilute the solution out and chill it so the silver chloride being held in solution by the strong acid may precipitate out.
It also helps to add sulfuric acid before that step(then filter) to remove lead in solution as lead sulfate.

Hoke is still spot on for the most part (99.999%) -read Daves (frugalrefiners) pdf version where the very very few things have been changed (dont use gas...dont refine in a basement..)

Hoke is old, not obsolete

Ice is also used/preferred before adding the smb (after agcl removal) as the process of precipitation is exothermic, and, if highly concentrated (gold per L) can get VERY hot and make the precipitation hit a wall--harold has a few posts on the matter

Edit to add: ice is suuuuuper cheap... Also, quite easy to make... I might have a recipe around here somewhere if you need it

 

[autumnwillow]

Chemical recipe? Not involving expensive stuff? Sure!

So as long as the beaker stays cool during SMB precipitation, ice doesn't have any other purposes?

 

[Topher_osAUrus]

Water+freezer+time=ice
Its perfect!

Ice serves the purpose of diluting the solution to remove agcl that is with the gold.

Also when precipitating it helps keep the solution cool and dilute to keep the SO2 gas in solution longer to help reduce the auric chloride back to elemental gold.

There may be other reasons, but those are the most prominent i believe

Edit for spelling and to add: those 2 ice additions are at different times. One before filtering out the lead sulfate and agcl that has ppt from solution.
The second is after the solution has filtered to crystal clear before adding SMB

 

[autumnwillow]

With your first two statements I think I could just dilute the gold chloride with distilled water then just put the beaker in a cold stainless steel bowl with cold water in order to keep it cool.

I really do not have ice.

 

[autumnwillow]

One more, why does everybody wait for the gold to settle (after precipitation in AR)? Why not just filter it right after checking negative for stannous? Are there any other chemical reactions happening while it is settling down?

 

[rewalston]

One more, why does everybody wait for the gold to settle (after precipitation in AR)? Why not just filter it right after checking negative for stannous? Are there any other chemical reactions happening while it is settling down?

You want to let it settle so that you can decant the barren solution. You do not want to filter it. Keep your powder in the beaker you precipitated it in, so that you can wash it with HCl until clear and wash it with water. There are multiple wash steps. Only after it's washed and dried in the beaker do you move your powder to your melting dish. Constantly moving it to different containers you have a greater chance of loosing some of your gold.

Rusty

 

[Topher_osAUrus]

One more, why does everybody wait for the gold to settle (after precipitation in AR)? Why not just filter it right after checking negative for stannous? Are there any other chemical reactions happening while it is settling down?

You want to let it settle so that you can decant the barren solution. You do not want to filter it. Keep your powder in the beaker you precipitated it in, so that you can wash it with HCl until clear and wash it with water. There are multiple wash steps. Only after it's washed and dried in the beaker do you move your powder to your melting dish. Constantly moving it to different containers you have a greater chance of loosing some of your gold.

Rusty

+1, rusty nailed it with his words of wisdom.
The more you move your gold, especially filtering, the more you misplace.

And yes, i suppose you could dilute to 3x the volume with cold water snd allow it to chill and have the silver chloride settle out overnight.

Patience is a key aspect of this field. Allowing stuff to settle well overnight will help your accountability per lot...if thats something you do anyways, everyone is different

 

[Grelko]

With your first two statements I think I could just dilute the gold chloride with distilled water then just put the beaker in a cold stainless steel bowl with cold water in order to keep it cool.

I really do not have ice.

If it's still cold where you live, you could always dig a shallow hole in the ground, and set the steel bowl in it. The coldness of the ground would transfer through the bowl and help cool the solution down more.

Edit - My grandmother had an underground fruit cellar, which stayed right around 48-50 F all year long.

 

[Palladium]

The cold solution will produce a slower nucleation of seed crystals which leads to larger grain and particle sizes. The larger grains will settle, filter and wash easier. A hotter solution will produce a more rapid formation of crystals leading to a smaller finer particle sizes which can be more difficult to settle and filter. This is from a cleaner solution with few contaminates. Add more contaminates to the equation with an addition of heat and the whole thing can get crooked sideways quick as far as nucleation goes.

 

[nickvc]

The best method I have seen is to wash your precipitated powders with water until no colour is seen then add cold HCl and put on a stirrer plate to keep the powders moving, do this several times decanting and washing inbetween new additions of HCl until the HCl takes on no colour.
This was Lou's method and it works very well, much better than hot HCl.

 

[Anonymous]

*coughs* where did you see the stirrer idea? 8) 8)

 

[nickvc]

U tube :roll: :lol:

Ok at yours, but it works and that's what matters 8)

 

[Anonymous]

lol. 8)

 

[autumnwillow]

Can I use my stirring rod for washing with HCL? I don't have a magnetic stirrer yet. Hehe

Almost there!! Could have finished it today if it wasn't for that very slow filtering process. Took me a while.
Gold has already settled at the bottom of the beaker. Tested negative for stannous. I think this AR waste has no more values?

Also, I though Platinum dissolves in nitric when alloyed with silver, this lot was from inquarted gold jewelry scrap. Or maybe the white powder is something else?

 

[nickvc]

You can use your stirrer rod but it means spending time manually stirring the powder, you only need to add enough cold HCl to cover plus about 5 cm more.

 

[autumnwillow]

You can use your stirrer rod but it means spending time manually stirring the powder, you only need to add enough cold HCl to cover plus about 5 cm more.

I'll shake the entire beaker then. Heh.

 

[autumnwillow]

The cold water in a stainless steel bowl worked during gold precipitation with SMB dissolved in distilled water!

 

[Topher_osAUrus]

Even if it shows negstive for stannous, id still throw it in my stock pot a couple days.

But, thats just me, i dont want to throw the baby out with the bathwater

 

[autumnwillow]

On my cold HCL wash there was no color change at all, I did it twice just to be sure.
I also did cold ammonia wash twice. More than 4 distilled water rinses. What I did was 2 boiling rinses, then 2 cold rinses.

This is my first button by the way. Weighs 124.50g. Tried to alloy it to 14k as a 99.9 gold, then tested on a touchstone. It tested ok but I still need to find an assay lab as I want to know the exact purity of my work.