Help with precipitation.

Gold Refining Forum

Help Support Gold Refining Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.
Joined
May 26, 2023
Messages
5
Location
UK
Hi, you seem like a great community and I've already seen lots of great advice on here. I'm new to this community and to the gold extraction process but have always been fascinated by it and thought I'd like to give it a try. My knowledge of chemistry is very little to none but ive read C.M Hokes's book.

I know people frown upon it, but I'm the type of person who learns from doing not reading so I decoded to give the extraction a try on a very small scale of course. I got 150 or so gold plated sim cards, placed them in a beaker with 50% water and 50% nitric acid. The gold flakes came off the cards within ten or so minutes. I left the solution for about an hour so the stubborn flakes all came off then I filtered the flakes out of the solution on filter paper. Once I had collected the flakes I made a small quantity of aqua regia at 3 parts hcl to 1 part nitric acid. I put the flakes into a beaker and poured on just enough aqua regia to cover them and dissolve them. Next I cotton filtered that solution into another beaker.

This is the part I'm struggling with. I understand that in order to precipitate the gold out of the aqua regia I need to add sodium metabisulfite. So I got a small beaker with some water, dissolved a teaspoon of metabisulfite into it then slowly poured it into my filtered solution whilst stirring. Almost immediately I could see the reaction take place and saw the black gold flakes starting to precipitate. This is where I think I made the mistake. I continued pouring the metabisulfite solution into the mix and suddenly it changed back to a yellowish liquid and I could no longer see any gold flakes.

Is there a fine line when pouring in the metabisulfite where as soon as you see the reaction you must stop and ultimately did I end up pouring in too much? If so how do i now precipitate the flakes out of my now yellowish solution? Any help or advice would be greatly appreciated 🙏
 
Hi, you seem like a great community and I've already seen lots of great advice on here. I'm new to this community and to the gold extraction process but have always been fascinated by it and thought I'd like to give it a try. My knowledge of chemistry is very little to none but ive read C.M Hokes's book.

I know people frown upon it, but I'm the type of person who learns from doing not reading so I decoded to give the extraction a try on a very small scale of course. I got 150 or so gold plated sim cards, placed them in a beaker with 50% water and 50% nitric acid. The gold flakes came off the cards within ten or so minutes. I left the solution for about an hour so the stubborn flakes all came off then I filtered the flakes out of the solution on filter paper. Once I had collected the flakes I made a small quantity of aqua regia at 3 parts hcl to 1 part nitric acid. I put the flakes into a beaker and poured on just enough aqua regia to cover them and dissolve them. Next I cotton filtered that solution into another beaker.

This is the part I'm struggling with. I understand that in order to precipitate the gold out of the aqua regia I need to add sodium metabisulfite. So I got a small beaker with some water, dissolved a teaspoon of metabisulfite into it then slowly poured it into my filtered solution whilst stirring. Almost immediately I could see the reaction take place and saw the black gold flakes starting to precipitate. This is where I think I made the mistake. I continued pouring the metabisulfite solution into the mix and suddenly it changed back to a yellowish liquid and I could no longer see any gold flakes.

Is there a fine line when pouring in the metabisulfite where as soon as you see the reaction you must stop and ultimately did I end up pouring in too much? If so how do i now precipitate the flakes out of my now yellowish solution? Any help or advice would be greatly appreciated 🙏
Welcome to us.

We never use Aqua Regia, AR in premixed form.
The premix will almost always mean you have to much Nitric in the liquid.

For your issue it might come from that by over adding your SMB you neutralize the acid to a level where it can no longer form SO2 which is the active ingredient precipitating the Gold.
If you have done your studies you might have picked up on this.
Anyway you might save the situation by adding enough HCl to re acidify your solution.
 
Hi, you seem like a great community and I've already seen lots of great advice on here. I'm new to this community and to the gold extraction process but have always been fascinated by it and thought I'd like to give it a try. My knowledge of chemistry is very little to none but ive read C.M Hokes's book.

I know people frown upon it, but I'm the type of person who learns from doing not reading so I decoded to give the extraction a try on a very small scale of course. I got 150 or so gold plated sim cards, placed them in a beaker with 50% water and 50% nitric acid. The gold flakes came off the cards within ten or so minutes. I left the solution for about an hour so the stubborn flakes all came off then I filtered the flakes out of the solution on filter paper. Once I had collected the flakes I made a small quantity of aqua regia at 3 parts hcl to 1 part nitric acid. I put the flakes into a beaker and poured on just enough aqua regia to cover them and dissolve them. Next I cotton filtered that solution into another beaker.

This is the part I'm struggling with. I understand that in order to precipitate the gold out of the aqua regia I need to add sodium metabisulfite. So I got a small beaker with some water, dissolved a teaspoon of metabisulfite into it then slowly poured it into my filtered solution whilst stirring. Almost immediately I could see the reaction take place and saw the black gold flakes starting to precipitate. This is where I think I made the mistake. I continued pouring the metabisulfite solution into the mix and suddenly it changed back to a yellowish liquid and I could no longer see any gold flakes.

Is there a fine line when pouring in the metabisulfite where as soon as you see the reaction you must stop and ultimately did I end up pouring in too much? If so how do i now precipitate the flakes out of my now yellowish solution? Any help or advice would be greatly appreciated 🙏
Here is something for you to study, take it as Ms Hoke recommended.
Try small experiments and make a plan on what you expect to happen and if it do not go as expected, revisit and see if you find out why.

Read the safety section of the forum: Safety
And then read about "Dealing with waste" in the forum: Dealing with Waste

Suggested reading: The Library

Forum rules : https://goldrefiningforum.com/threads/gold-refining-forum-rules.31182/post-327766
 
Thankyou for your reply and advice. So in future am I best to add hcl onto the flakes and slowly add nitric acid into it until the flakes start to dissolve so as not to put too much nitroc acid into the mix? So if I was to add more hcl to my mixture then try to add sodium metabisulfite again this may work? Would I add the metabisulfite Straight into it or dissolve in water again then slowly add?
 
Thankyou for your reply and advice. So in future am I best to add hcl onto the flakes and slowly add nitric acid into it until the flakes start to dissolve so as not to put too much nitroc acid into the mix? So if I was to add more hcl to my mixture then try to add sodium metabisulfite again this may work? Would I add the metabisulfite Straight into it or dissolve in water again then slowly add?
You may not even need to add more SMB, it is already there waiting for the right conditions.
And when you look at foils HCl/Bleach or HCl/Peroxide will do the job with no issues regarding surplus oxidizer.
SMB will precipitate the equal amount of Gold as it self, 1g SMB will drop 1 g Gold.
With too much Nitric, this will change since the Gold will drop and redissolve,
until the Nitric is spent or the solution moves beyond its acceptable pH range.
 
Again, thanks for the help. I'll try adding more hcl to the mix and see if I manage to get the gold to precipitate. I will keep you updated on my progress.
 
Again, thanks for the help. I'll try adding more hcl to the mix and see if I manage to get the gold to precipitate. I will keep you updated on my progress.
Be ware, you might be hard pressed to see the Gold, very little in the plating.
Usually most of the Gold will/may be in the chips.
 
For future attempts when making the aqua regia am I best to pour the hcl over the flakes then add just the tiniest of nitric acid to make the flakes dissolve so as not to over do the nitric acid concentration?
 
For future attempts when making the aqua regia am I best to pour the hcl over the flakes then add just the tiniest of nitric acid to make the flakes dissolve so as not to over do the nitric acid concentration?
If you want to use AR, yes. But is should be used on hot not, boiling AR.
But if you can, for foils both Peroxide or Bleach is quite sufficient as oxidizer in the HCl.
 
Hi, you seem like a great community and I've already seen lots of great advice on here. I'm new to this community and to the gold extraction process but have always been fascinated by it and thought I'd like to give it a try. My knowledge of chemistry is very little to none but ive read C.M Hokes's book.

I know people frown upon it, but I'm the type of person who learns from doing not reading so I decoded to give the extraction a try on a very small scale of course. I got 150 or so gold plated sim cards, placed them in a beaker with 50% water and 50% nitric acid. The gold flakes came off the cards within ten or so minutes. I left the solution for about an hour so the stubborn flakes all came off then I filtered the flakes out of the solution on filter paper. Once I had collected the flakes I made a small quantity of aqua regia at 3 parts hcl to 1 part nitric acid. I put the flakes into a beaker and poured on just enough aqua regia to cover them and dissolve them. Next I cotton filtered that solution into another beaker.

This is the part I'm struggling with. I understand that in order to precipitate the gold out of the aqua regia I need to add sodium metabisulfite. So I got a small beaker with some water, dissolved a teaspoon of metabisulfite into it then slowly poured it into my filtered solution whilst stirring. Almost immediately I could see the reaction take place and saw the black gold flakes starting to precipitate. This is where I think I made the mistake. I continued pouring the metabisulfite solution into the mix and suddenly it changed back to a yellowish liquid and I could no longer see any gold flakes.

Is there a fine line when pouring in the metabisulfite where as soon as you see the reaction you must stop and ultimately did I end up pouring in too much? If so how do i now precipitate the flakes out of my now yellowish solution? Any help or advice would be greatly appreciated 🙏
Sim cards contain very little gold. Gold precipitate is brown, not black.
The reducing agent is S+4, by giving electrons it converts to S+6, both in dissolved form. There is a possibility for little gold to dissolve back in sulfite solution. SO2 gas, formed by acid action has a nasty smell which tells you if you used excess SMB
 
Back
Top