Gold stripping with iodine

[Goldfinger4]

Hello!

I tried to strip gold plated spoons with a iodine / potassium iodide solution. 4g potassium iodide : 1g iodine : 40ml water.
Nothing happened after weeks. Only some red christals formed on the spoons surface.
What went wrong? Did someone try this process?

 

[butcher]

Maybe your leach is saturated, I have never used this leach but the way i understand it the red brown solution is gold in solution, if you remove this liquid and add sodium hydroxide the solution should go clear (sodium Iodide), and the gold should precipitate as a black powder.


edit after thought:
What makes you think the gold will leach and leave the base metals?
I would think the base metals would go into solution much easier than gold.
if my guess is correct your black powders may just be base metals or very contaminated if it did have gold.

I have not studied or worked with this leach so I am just speculating my thoughts.

 

[Goldfinger4]

Gold and iodine form a complex (like Cl), HI is a weak acid and should not react with base metals.
Potassium iodide is necessary to make iodine soluble in water.
I don't know why it did not work.. maybe the spoons are varnished.

 

[butcher]

Incineration, hit one with a torch, then try again.
Are you oxidizing with air?

I have not studied much about iodine or iodide, but it is a halide like chlorine, what I do not understand is why would the iodine leach not dissolve copper or iron if these metals were oxidized? it apperars to me gold would be more inert that many of these other metals to any halogen, and if we oxidized the gold why would we not be oxidizing these other base metals to where the halogen iodine would form iodides salts with these other base metals in your spoon?

 

[Lino1406]

1. A stirrer + heating + time are essential for operation
2. After 1st alkali precipitation, rinse with water and acidify
once to get rid of iodine left (you'll see violet color), make alkaline
once more to neutralize iodine.
Lino1406, author of "25 recovery procedures"

 

[Goldfinger4]

I will try heating.
Did you try this method for yourself?

 

[Lino1406]

It will not prooceed without permanent
stirring.

 

[Goldfinger4]

Ok..
I will try it again and make some photos

 

[NoIdea]

Hello - I have tried a number of iodine recipes, personally i am not fond of the process, however, you may want to bring the stripping bath up to 35-40C.

Room temperature stripping rate is approximately 1um/min.

Au is dropped using citric acid and the solution is regenerated using hydrogen peroxide, and pH plays a big part as well.

US Patiant 3957505 and 4319923 outline the process pretty well.

Cheers

Deano