Gold Refining

[GAHD]

I was looking into gold refining and came across a lot of information on Aqua Regina. While I found quite a feww step-by-step articles, I have yet to find anything that explaines exactly why mixing these acids can dissove gold.

Anyone care to lent this old phogy some help in the matter? (pardon the pun)

[gpdone]

It's been awhile but this may serve as a starting point;
Fisrt of all I've never heard of Aqua Regina out side of classical Lit. It sounds like a brand name for something. If it is uric acid in solution that would make sense heap leaching gold wise as uric acid acts to corrode (oxidise) iron in which much native lode gold is found in association. In addition uric acid or urea the chrystal when heated during electrolysis produces cyanide (the primary agent for leaching processes for precious metals)which further creates micron gold for deposition on the plates. This is from years ago research into mining methods and hopfully will be clarified or corrected by a for real Chemist!
Good luck,

Lee

PS DONT try this at home. Cyanide is DEADLY even in small amounts so no heating you urin on the stove just to see what happens!;-)

[Tim_Lou]

yeah, cyanide performs a complexation reaction with gold.
well, i dont know much, here is some info found on the internet:
http://doccopper.tripod.com/gold/AltLixiv.html

"Au + 2CN - = Au(CN)2 - + e -"
the gist of the whole article. : )
*notice Au(CN)2- is (CN)2, not 2- charged.

[Tim_Lou]

btw, cyanide is really poisonous, pure hydrocyanic acid (HCN, a gas actually) can kill a person in minutes.

"Cyanide gas is highly flammable and reacts violently in some situations (e.g., a largeamount of cyanide gas mixed with air may suddenly explode). There is an extremelyhigh risk of explosion if cyanides are exposed to heat or flames. Most of the safetyprocedures are aimed at preventing the substance from entering the human body andavoiding situations where cyanide solids or liquids might react to produce the highlypoisonous and flammable cyanide gas."

all credit from:
http://www.safetyline.wa.gov.au/page...zshazd0005.pdf

[GAHD]

My bad, Aqua Regia (Royal Water), not Aqua Regina.

From what I've gathered it's made with 1 part nitric acid to every 4 parts muriatic acid.

Gold will not dissolve in either of these acids alone but will dissolve when they are mixed into Aqua Regia.

Aqua Regia is also used for etching of other metals, but is relatively useless for dissolving Silver.

[GAHD]

*bump*

[UncleAl]

Aqua regia "royal water" is 3:1 HCl/HNO3 vol/vol that after mixing rapidly evolves nitrosyl chloride, (NOCl) and chlorine. Nasty and hazardous.

Dissolution of gold requires oxidation and complexation. Brine and air or hydrogen peroxide will do it (tetrachloroaurate(III) as end product), so will cyanide and air (tetracyanoaurate(III)). Aqua regia is a buzz saw for metallic gold, giving tetrachloroaurate(III) as end product. Metallic gold is typically recovered by oxalate reduction. Platinum is unaffected.

Presence of ammonia during gold recovery will lead to "explosive gold" with roughly the sensitivty and power of lead azide.

[GAHD]

'Buzz saw"? You mean just that it reacts quickly?

also,do you think I could recover pure gold from the end product with electrolysis?

[Turtle]

It is possible to recover gold from findings left from sluicing by simple smelting.

[thaupt]

I have been thinking of refining my own platinum and gold... I have found an interesting and not to expensive "Home refining" kit. The link is... well i was going to post a link... but the system will not let me. What I did was a google search for...

home gold refining

and found this.

shorinternational dot com slash RefineStart dot htm

It seems simple enough and no harsh chemicals always a plus.