Gold Washing & Melting

[sander]

Couple of questions for you guys,

So I recently recovered gold from some PCB's, gold plated jewelry and other gold barring items using the Shor international aqua regia method. So my first question concerns the washing of gold with ammonia. After I had precipitated the gold I was told to wash it with ammonia then water a few times. The first time I did this I only had the "cloudy" household ammonia (I read later that cloudy ammonia contains some sort of soap in it?). When I did this it turned the brown powder a odd green color. Not a copper oxide green but a darker green. I rinsed it with water and then again with regular ammonia but it still was green. This was the first batch that I filtered out from the acid solution after precipitation. The following 3 batches all stayed brown. Any idea why the cloudy ammonia tainted the color so badly?

Second question: After drying the brown powder I tried to melt some using my Lost Foundry propane furnace which melts copper, brass and bronze without any problem. When I did this I let the powder heat up for a long time a lot longer then it would take copper to melt and after all I had was ash that when cooled and crushed looked nearly identical to the brown gold powder I started with. I have read that you should use a boric acid flux or something along those lines. Is this 100% necessary in order for the gold to melt properly? Copper has a higher melting point then gold by about 40 degrees F. Therefore, the temperatures reached during the melting process are adequate. Did it not melt properly simply BC of the lack of boric acid?

Any help and information would be greatly appreciated!

Thanks! :?:

 

[JHS]

Hi Sander,
On behalf of the forum I would like to welcome you
It is the best place in the world to learn the art of refining and recovery of presious metals.
The forum is just chock full of helpful and the most accurate information you will find, no where else, in the world.
Such as the safety section,and the guided tour.also there is a link to Hoke's book that will teach you most all of what
you will need to know.
Unless you have a photographic memory,it will take some time to learn the proper procedures,and how and when to use them.
Take your time studing and learning them and then you will be very sucessful at this interisting art.
Always remember safety first.
By the way cussing is not allowed,words like ,boiling,and urea,are prime examples.lol
as you read you will understand what i mean.
If you will read the introduction you will understand that you can find all the answers to your questions .

I wish you great luck and prosperity in your future endevors.

 

[butcher]

sander,
I believe they do have some household ammonium hydroxide brands that do contain soaps or scents.
but you can get cheap ammonium hydroxide brands with basically just ammonia dissolved in water with no soaps forming ammonium hydroxide.

I cannot say for sure why the ammonia solution gave the green color when used, but it could have come from base metal in the gold, when you washed the acidic gold powders with the ammonium compound you could have formed hydroxides of any remaining acidic base metal salts...

You do not need to flux gold powders to melt, when the gold powders are fairly pure, pure gold will melt without flux (using only a wash coating of melted glass borax on the dish to keep gold from sticking).

I suspect you are seeing impurity in your gold powders.

Keep studying the forum and learn better methods to get the gold recovered and refined to high purity.