Today's gold refinement

[Alexander_Hun]

Hello!

I will share with you my refinement today, I will show you in pictures what the raw material is and what the end result is.

I hope what I show is not boring!

Have a nice day!


(
I have a question, after reducing the gold dust, I deliberately wash it first in distilled water and then in hydrochloric acid, I noticed that boiling with hydrochloric acid dissolves all the gold....
I don't understand why, the liquids turned yellow, I tested with stannous chloride and it contained gold...
I poured off the gold dust, added SMB, and a fairly black powder was reduced, it's not the first time this has happened to me, I don't understand what the problem could be.
I cleaned the black powder and melted it into gold..)


Raw materials::




Process:
View attachment 20220822_135816.mp4

What was dissolved by hydrochloric acid boiling and then reduced by SMB:



Final result:

 

[Shark]

Some nice materials. And definitely not boring.

 

[Alexander_Hun]

What I forgot was 600 grams before all the refinements

 

[Shark]

What I forgot was 600 grams before all the refinements

That is some good material, right up there with gold-filled.

 

[Alexander_Hun]

Hi!

Does anyone have any ideas for the above problem? Gold dust boils in hydrochloric acid and gold dissolves, why is this? Before that, I boil it in distilled water to wash out the remaining nitric acid.

 

[Shark]

PH test your water washes. As long as they test acidic change the water and boil again.
Edit for spelling

 

[Alondro]

Hi!

Does anyone have any ideas for the above problem? Gold dust boils in hydrochloric acid and gold dissolves, why is this? Before that, I boil it in distilled water to wash out the remaining nitric acid.

I always recommend the HCl + bleach method to dissolve gold foils to those who cannot obtain sulfamic acid to denox AR. Excess nitric can be a pain to get rid of completely without it. But with HCl + bleach, you just lightly boil it in bright sunshine for 2 hours, and the excess chlorine is gone! Simple and VERY cost-effective. Bleach is only a small fraction of the price of nitric.

Sulfuric acid is good for cleaning the gold powder. (But before dropping gold from the solution, add a few drops of sulfuric and let it settle overnight to remove any lead. Lead sulfate is COMPLETELY insoluble in water). IT WILL NOT DISSOLVE GOLD AT ALL. Sreetips boiled the heck out of gold in sulfuric for hours, and NONE dissolved. But it DOES get rid of trace base metals like copper and tin.

I save my nitric only for silver, palladium, and (eventually) platinum (when I have enough Pt-containing material to process).

 

[Alexander_Hun]

Hi! What is this mud? There is quite a lot in it, it clogs the filter when I pour out the excess liquid. It mixes with the gold dust, it is almost impossible to separate them

 

[Yggdrasil]

Hi! What is this mud? There is quite a lot in it, it clogs the filter when I pour out the excess liquid. It mixes with the gold dust, it is almost impossible to separate themView attachment 51864

How did you create the mud?
HCl, Nitric or something else?

 

[Alexander_Hun]

How did you create the mud?
HCl, Nitric or something else?

Just nitric acid, I pour it on the gold-plated contacts. It starts to dissolve them and that's when the mud is formed

 

[Yggdrasil]

It seems you did not dissolve the tin first.

Tin and Nitric creates Metastannic acid, which is a nightmare to filter.
You can roast it and the dissolve the Tin Oxide with HCl and then filter it.
Then you should have clean foils and "dust".
After that, dissolve as per your preference.

 

[Alexander_Hun]

It seems you did not dissolve the tin first.

Tin and Nitric creates Metastannic acid, which is a nightmare to filter.
You can roast it and the dissolve the Tin Oxide with HCl and then filter it.
Then you should have clean foils and "dust".
After that, dissolve as per your preference.

Thanks, can't the contacts also contain tin? Maybe some tin alloy?

 

[Alondro]

It seems you did not dissolve the tin first.

Tin and Nitric creates Metastannic acid, which is a nightmare to filter.
You can roast it and the dissolve the Tin Oxide with HCl and then filter it.
Then you should have clean foils and "dust".
After that, dissolve as per your preference.

Yep, found that out by accident when I first did a small plated electronics dissolve. I'd only processed some jewelry previously, and was stumped as to what the strange goo was. On a hunch, I burned all the goo and gold dust, then discovered all the roasted goo vanished with a little HCl, leaving the gold behind. Wasn't until later I came upon the identity of metastannic.

 

[Yggdrasil]

Thanks, can't the contacts also contain tin? Maybe some tin alloy?

Of course especially if they are plated on bronze.

 

[Alondro]

Of course especially if they are plated on bronze.

Yeah, that's why it's always best to get rid of the base metals first with the HCl-Cucl2 method. Then you have lovely, mostly clean foils to process.

 

[Alexander_Hun]

Yeah, that's why it's always best to get rid of the base metals first with the HCl-Cucl2 method. Then you have lovely, mostly clean foils to process.

Hi, can you write about the process? This is the first time I've heard it, I'd be interested

 

[Alondro]

Hi, can you write about the process? This is the first time I've heard it, I'd be interested

It's pretty simple. You just put all the gold-plated parts in a beaker, cover with concentrated HCl, then add a little copper chloride-rich HCl waste from a previous dissolve to jump-start the reaction. Cover and warm to about 90C, or just let it sit in a warm place. You'll see the solution go from pale yellow-green to dark brown in a day or two once the reaction gets going. You can let it sit longer, and the CuCl2 that forms will attack copper even more. The best batch I had eventually dissolved all the base metal in a batch of pins and left foils and white-translucent Cu(I)Cl crystals, which were easily washed away with two small HCl washes to dissolve them.

After that, the foils were all clean and ready for fine purification.