finishing.com logo
    HOME / sitemapFAQsBOOKSHelp WantedsAdvertiseContact   you are here: Hotline/Forum => Letter 16370
most fun in metal finishing

Can gold be dissolved in sulphuric acid alone?

++

Q. Dear All,

I have a wager to settle to with a friend and so quite a basic question really, I would like to know very simply if gold can be dissolved in sulphuric acid or is it really only aqua regia that can do this?

Thank you for your help in advance and have a lovely day.

Best regards,

Patrickdeleted
WMRC - London, UK


++

A. No winner; donate the kitty to charity :-)

Gold cannot be dissolved in sulphuric acid to my knowledge; but it can be dissolved in a number of things other than aqua regia, including cyanide and citrates.

pic of Ted Mooney Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey

++

A. No. The only acid that dissolves gold is aqua regia. How much did you win?

Ted is of course right. Gold will dissolve in cyanide and citrates but, as far as I am aware, only with the application of an electric current.

Trevor Crichton
R&D practical scientist
Chesham, Bucks, UK

Recovery And Refining Of Precious Metals


August 2014

thumbsup2Thanks for correcting me so gently, Trevor. Surely I was guilty of mental sleight of hand when I tried to equate using electricity and cyanide to dissolve gold with dissolving gold by simple immersion in aqua regia.

Regards,

pic of Ted Mooney Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey


September 16, 2014

! Trevor Crichton, Gold dissolves in cyanide solutions without application of electric current. Witness use of weak cyanide solutions for recovery of gold by heap leaching.

Fuzail Siddiqui
Independent Consulting Geoscientist - Markham, Ontario, Canada


March 7, 2012

"Can gold dissolve in sulfuric acid alone?"

A. The answer is yes, and no. According to a 1940 patent #2185858, gold or palladium are stripped from a copper based substrate by making the parts anodic in a fairly concentrated sulfuric acid solution. According to the patent, persulfuric acid is produced at the anode surface, which momentarily dissolves the gold. Once away from the anode, the dissolved gold immediately reduces to a powder. When all the gold has been stripped from the parts, the current goes to zero. All the gold powder settles to the bottom and is then collected.

I guess the keyword in the original question is "alone." The gold does dissolve, using no other chemical than sulfuric, but it does require electrolysis.

I have used this stripper many 100s of times for gold recovery from plated objects. It works for many substrates besides copper, even aluminum.

Chris Owen
- Nevada, Missouri, USA


December 8, 2012

A. Sulfuric acid can dissolve gold, but it is a very dangerous process as the sulfuric acid has to be concentrated and heated to the point sulfur dioxide gas is fumed off, silver or gold will dissolve gold will form a gold persulfate soluble in the very concentrated acid, upon dilution the gold will precipitate out of solution as a powder which can be washed and refined. (Another terribly dangerous process) (never add water to concentrated sulfuric acid a steam explosion of hot acid can go everywhere)(always add acid to water slowly to dilute), concentrated boiling sulfuric acid can disable a man for life,and a little bit of gold is not worth the risk.

Another way gold is dissolved in concentrated sulfuric acid is by making the gold an anode the persulfate that forms at the anode will dissolve the gold into solution as gold persulfate, but as these gold ions migrate towards a lead cathode the gold is no longer a persulfate in the more dilute solution away from the anode, so the gold will precipitate in the cell, again gold is recovered by dilution of the acid (see warnings above), this impure gold is washed and then refined

People who would re-plate silver would use a process similar to this to remove the silver from copper or brass items (the concentrated sulfuric would not attack the copper or brass (as long it was kept concentrated), they would use electrolysis and about 5% HNO3 added to the electrolyte to strip the silver plate, silver plated article was on the anode.

To dissolve gold or platinum there are several ways to do this besides aqua regia.
Aqua regia is not the only thing strong enough to dissolve gold and form a gold chloride solution.

HCl and NaCLO 5% sodium hypochlorite (household bleach) will also dissolve gold and form gold chloride

HCl and 30% H2O2 Hydrogen peroxide will also dissolve gold to form gold chloride

There are other oxidizers that will work.

There are even salts that when fused with gold can make the gold water soluble when the fusion is dissolved into water.

Richard Butcher
- Grants Pass, Oregon, USA



January 20, 2009

Q. My dog ate my gold earring and has not passed it after one week. I understand that he has a pocket at the bottom of his stomach for hard to digest materials to linger while his stomach acids break them down. My question is, will my dog's stomach acids dissolve the gold earring?

Kathy Mdeleted
- West Palm Beach, Florida


January 21, 2009

Hi, Kathy. You might talk to a vet; I don't think your dog's stomach has the capacity to dissolve gold.

Regards,

pic of Ted Mooney Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey

January 22, 2009

thumbsup2Thank you for your response. Seems like a good blog, although most are probably trying to stay warm rather than typing with cold fingers!

Kathy M [returning]
- West Palm Beach, Florida


January 26, 2009

Hello Ted,
Thought I would let you know the outcome of my dog swallowing the earring. Yesterday my dog walked out into the kitchen to exactly where I stand to dish up his food and left my gold earring on the floor for me to find ! I happened to be watching him out of the corner of my eye and he just set it down and walked away. Since I had cleaned the house from top to bottom, we are for sale down here, the only thing I did not do was check "in his bed" ! I don't know where it came from, but I would have to guess that he had taken it back there to play with. In perfect condition, both the earring and the dog ~..~ Thank you for answering my inquiry, stay warm. Best Regards.

Kathy M (returning)
- West Palm Beach, Florida


January 27, 2009

Hi, Kathy. Thanks for sharing the happy ending.

Regards,

pic of Ted Mooney Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey

November 3, 2009

Interesting reading about the dog.

When you say it brought put the ear-ring on the kitchen floor, do you mean that it carried it in in its mouth, and put the ear-ring on the floor ?

or ... he did his Doggy Duty on the kitchen floor, and his special gift contained the ear-ring ?

I had food poisoning twice in 2002. I learned more than I would have liked about stomach acid.

What I was looking for was info about dissolving gold, what types of solvents & acids work.

Lots of good info here !

Roger Baer
- Santa Rosa, California



March 2, 2012

Q. Hi,

I would like to know can I dissolve gold using potassium iodide (KI)+ iodine (I2)+ H2O?

Regards
Adriano

Adriano Tan
- Jakarta, Indonesia


March 7, 2012

A. Yes, KI + I2 is a common gold stripper, especially in the electronics industry. These chemicals are quite expensive, but there schemes which precipitate the gold and rejuvenate the solution for further stripping.

Chris Owen
- Nevada, Missouri, USA

ADD a Q or A to THIS thread START a NEW THREADView This Week's HOT TOPICS

disclaim

 seek

JobshopsCapital Equip. & Install'nChemicals & Consumables Consult'g, Train'g, SoftwareEnvironmental ComplianceTesting Svcs. & DevicesUsed & Surplus


©1995-2014 finishing.com     -    Privacy    -    Search