Complications, first aqua regia use

If you need help with the processes...
boarteats
Member
Posts: 36
Joined: March 31st, 2018, 11:24 pm
Country of Origin: United States

Complications, first aqua regia use

Postby boarteats » June 12th, 2018, 10:15 pm

Had a bit of a hiccup using aqua regia for the first time to recover gold from concentrates. Just want to run this by more experienced folks to ensure that I'm not missing something.

Made some beautiful aqua regia with muriatic acid and concentrated nitric acid with a 4:1 ratio. Let concentrates soak for a day or so with regular mixing. Then, poured off and filtered aqua regia into glass jar. Next step is where I had a misstep.

Next, I added SMB to filtered AR neglecting to neutralize nitric first with urea. Realized my mistake (eventually) when the gold that started to drop out of solution immediately re-dissolved into solution. After recognizing my error, I added urea to aqua regia slowly until the urea no longer reacted with solution. As I added the urea, solution color started to change to a golden yellow color and brown powder precipitated out of solution. Assuming that brown powder is the gold. After fully neutralizing nitric with urea, I added additional SMB until it no longer reacted. I likely added too much SMB in the end. In addition to brown powder, white material also precipitated out of solution. So, now I have both brown powder and this white material collecting on the jar bottom. I'll let this sit for a day or so.

Due to my error, will there be any foreseeable problems/complications washing the precipitated gold first with muriatic acid and then water and otherwise preparing the gold for melting? Should I consider redissolving any precipitated material in fresh AR and then reprecipitate gold more carefully?


User avatar
Palladium
Active Member
Posts: 5223
Joined: January 17th, 2008, 1:54 am
Location: USA

Re: Complications, first aqua regia use

Postby Palladium » June 12th, 2018, 11:36 pm

Drain the solution. Add warm water to dissolve crystals that will and let settle. Siphon off excess liquid leaving the gold and last little bit of solution, it don't have to be perfectly clean. Redissolve and re precipitate. Then wash!
The difference between stupidity and genius is that genius has its limits. Albert Einstein
1. Refining Precious Metal Wastes C.M. Hoke http://tinyurl.com/mfnyhs
(REV) (Free Download)
2. Get the (FREE) Gold Refining Forum Handbook VOL 1 here >> http://tinyurl.com/nyutnp
3. Get the (FREE) Gold Refining Forum Handbook VOL 2 (Final) here >> http://tinyurl.com/y9w5y73
4. Silver cell setup video here (FREE) >> https://tinyurl.com/jhzadse
ALL FREE-----ALL THE TIME

kernels
Active Member
Posts: 525
Joined: April 14th, 2016, 7:12 am
Country of Origin: New Zealand
Location: Auckland, New Zealand

Re: Complications, first aqua regia use

Postby kernels » June 13th, 2018, 1:35 am

Do not pre-mix Aqua Regia, cover your material with HCl and add HNO3 as required until all the Gold is dissolved.

Get into the habit of testing solutions with SC so you know where the Gold is.

Sulfamic acid has some benefits over Urea for denoxxing.

You only usually need 2g or so of SMB for every expected gram of Gold (This varies a bit, but a good guideline)

Test for when HNO3 is fully denoxxed by adding a small Gold button to the solution and observing when it stops dissolving.

Yes, you should be able to was all the excess SMB and Urea out with enough clean warm water.

Keep in mind that you are creating more and more poisonous waste as you go.

boarteats
Member
Posts: 36
Joined: March 31st, 2018, 11:24 pm
Country of Origin: United States

Re: Complications, first aqua regia use

Postby boarteats » June 13th, 2018, 8:44 am

Great! Thanks palladium, kernel.

User avatar
g_axelsson
Active Member
Posts: 4449
Joined: November 17th, 2007, 8:46 pm
Location: Sweden

Re: Complications, first aqua regia use

Postby g_axelsson » June 13th, 2018, 3:36 pm

You never mentioned what kind of concentrates you had. If there is a lot of copper in solution then excess SMB can precipitate white copper chloride crystals. These will dissolve easily if you wash the powder with HCl.

Göran
Visit the GoldRefiningWiki, an online refining encyclopedia.
It also contains an online version of the book "Refining Precious Metal Wastes" by Hoke.


boarteats
Member
Posts: 36
Joined: March 31st, 2018, 11:24 pm
Country of Origin: United States

Re: Complications, first aqua regia use

Postby boarteats » June 14th, 2018, 8:15 pm

g_axelsson wrote:You never mentioned what kind of concentrates you had. If there is a lot of copper in solution then excess SMB can precipitate white copper chloride crystals. These will dissolve easily if you wash the powder with HCl.

Göran

Ahhhh... that could explain it. Gold, of course. Certainly, some copper. I think that I got most of the magnetite out beforehand. Lots of chromite. Wasn’t sure if this would be problematic. Some silver. Very annoyingly, manganese covering everything making it quite difficult to id material.

I washed precipitates with HCL and warm water. Haven’t had a chance to try melting yet.

Was a small batch, so I’m pretty much treating this as a good learning experience and will be more methodical next time!

User avatar
anachronism
Active Member
Posts: 1801
Joined: May 31st, 2016, 2:51 am
Country of Origin: England

Re: Complications, first aqua regia use

Postby anachronism » June 17th, 2018, 5:54 pm

Chromium causes issues precipitating from AR. You have to work hard at it and use lots of SMB.
If you keep on doing what you've always done then you'll just keep on getting what you've always got.

"If you can bear to hear the truth you’ve spoken twisted by knaves to make a trap for fools, or watch the things you gave your life to broken, and stoop and build ‘em up with wornout tools" -- Rudyard Kipling

"The best diplomat that I know is a fully-loaded phaser bank." -- Lt. Cdr. Montgomery Scott

boarteats
Member
Posts: 36
Joined: March 31st, 2018, 11:24 pm
Country of Origin: United States

Re: Complications, first aqua regia use

Postby boarteats » June 17th, 2018, 8:46 pm

anachronism wrote:Chromium causes issues precipitating from AR. You have to work hard at it and use lots of SMB.


Hrmmmm.... sounds like I have some additional research to do. There is sooooooo much chromite.

User avatar
Palladium
Active Member
Posts: 5223
Joined: January 17th, 2008, 1:54 am
Location: USA

Re: Complications, first aqua regia use

Postby Palladium » June 17th, 2018, 9:33 pm

You're going to melt it knowing it's not clean?
The difference between stupidity and genius is that genius has its limits. Albert Einstein
1. Refining Precious Metal Wastes C.M. Hoke http://tinyurl.com/mfnyhs
(REV) (Free Download)
2. Get the (FREE) Gold Refining Forum Handbook VOL 1 here >> http://tinyurl.com/nyutnp
3. Get the (FREE) Gold Refining Forum Handbook VOL 2 (Final) here >> http://tinyurl.com/y9w5y73
4. Silver cell setup video here (FREE) >> https://tinyurl.com/jhzadse
ALL FREE-----ALL THE TIME


Return to “Help Needed”

Who is online

Users browsing this forum: No registered users and 2 guests