Question for Harold

[lazersteve]

Harold,

My most recent electrolytic cell cleaning has left me with 22 grams of unrefined gold powder. It has hardened after drying for several days. I washed the powder with nitric before it dried. It now appears as a hard brownish purple 'kiss' (like the chocolate ones).

Here is a photo of it:

My question is should I go straight to the melting dish with a thin layer of borax on the dish or is there something else I should do before melting it? I don't want to have to use any flux if it's not required. The kiss is hard enough that it won't blow away under the wind of the torch. It seems that when I use the borax as I have been, the borax always comes out purple which I know is colloidal gold. In the past the gold has always been powdery which is partly why I used the borax to help keep it from blowing away.

I will be sharing a video of the process you prescribe with the forum.

Any advice you can give would be greatly appreciated. I'm working on breaking my old bad habits and moving towards more pure gold.

Thank you,

Steve

 

[Noxx]

I know my name is not Harold but when you get black powder, you don't have pure gold... If I was you, I would refine it using aqua regia to get 99.9%... Gold powder dissolves very fast in AR.
If you want pure gold, it's always better to refine it twice.

 

[Harold_V]

when you get black powder, you don't have pure gold...

That's not true. Gold, finely divided (colloidal), will be purple. For that matter, look through some gold leaf at your convenience. It, too, will appear purple. Steve has it right----the key is how finely the gold is divided----the color is not an indication of purity.

If I was you, I would refine it using aqua regia to get 99.9%... Gold powder dissolves very fast in AR.
If you want pure gold, it's always better to refine it twice.

Exactly! Plus, if you're seeking ultra high purity, it's a good idea to precipitate with two different methods. Each one will have a tendency to eliminate something that the other may not.

In fairness, I did not follow the different precipitation methods, although I always double refined my gold. I used sulfur dioxide to precipitate---which introduces nothing objectionable to the gold. That's not always true, such as when using ferrous sulfate. Works great, but is a pain to use. It also introduces iron, although it washes out fairly easily with HCL.

Harold

 

[Harold_V]

My question is should I go straight to the melting dish with a thin layer of borax on the dish or is there something else I should do before melting it?

My advice would be to further refine the gold. It's a perfect candidate for AR processing, being finely divided and already well washed with nitric. The end product from such refining is far easier to melt, and is generally of much higher purity. Very little will be found in your flux cover after melting, although you will always see a slight purple color from melting fine particles of gold, regardless of the source. Nothing is lost if you don't discard the flux and dishes.

We talked, previously, about your use of cupels to assist in purifying your gold. While that works to some degree, it is not the preferred method, although your extraction process is likely to produce relatively high quality gold, something I didn't understand all too well when I first read your posts. Be advised that if you get involved with silver, or if you have any of the PM group present, a cupel will not separate them from the gold. Eventually, you will move to AR refining, or start running a gold parting cell. It's the only way to guarantee high quality gold on a consistent basis if you refine from multiple sources, barring the Miller chlorine process, which is really beyond home shop application, to say nothing of the danger of its use.

If you don't discard the flux from melting gold, and other dirty alloys that tend to darken your flux, you can make a reasonable recovery of values eventually. I built a tilting furnace to facilitate such an operation. Here's a picture of the furnace, along with a couple large cone molds.

Harold

 

[lazersteve]

Harold,

Very impressive furnace!

I keep ALL of my leftovers. I have a good quantity (by my comparisons) of spent borax with a nice even purple color to it. Some is a deeper purple while most is lightly colored. In a previous post you mentioned ways to get the gold out of this flux. Could you be so kind as to repeat or reference that process for me again so I can make an attempt at recovering the gold out of my spent fluxes?

Thanks,

Steve

 

[Harold_V]

In a previous post you mentioned ways to get the gold out of this flux. Could you be so kind as to repeat or reference that process for me again so I can make an attempt at recovering the gold out of my spent fluxes?

The post was more concerned with cleaning dishes for re-use than recovering values, although each objective was accomplished in the process. It involves torch heating your dish to redness, then adding soda ash, which will dissolve the hardened borax, liberating metals in the process. It takes a little time, and stirring with a carbon rod helps. When you get the entire mess up to heat and the soda ash has done its work, it doesn't hurt to add some fresh borax to help make the slag less viscous. Pour off the entire lot into an assayers cone mold, then repeat if the dish isn't as clean as you'd like. You'll find a nice button of metal in the bottom of the cone mold, which will readily break free from the slag. That's the beauty of cone molds.

Remember, the soda ash will be correspondingly hard on the dish, which is constantly being dissolved, so you don't want to do this any more than necessary to clean the dish to satisfaction. When finished, coat the dish with a fresh layer of borax and it's ready to go back in service. Make sure the bottom isn't near breaking through.

Over the long term, your old dishes will need to be processed by one of two methods. One is to run them through a ball mill, then extract values with cyanide, or to run the crushed material in a furnace, fluxing very well. That's the purpose of the furnace in the picture that I posted recently. All of my waste material was incinerated, then combined with a mix of fluxes and fired. I experienced a very good recovery, in part due to including all my old filters in the waste. The silver chloride in the used filters, being reduced to elemental silver via the furnace, became the collector of the other values, including the platinum group.

Get yourself a large covered container that can be stored out of the way, then incinerate your wastes (to reduce the volume), then dump everything in this container. Eventually you'll have a place where you can run a large furnace, at which time you can run the waste material and extract the values. You'll be shocked at the savings plan's effectiveness. I saved my wastes for over 20 years before running them in the furnace. You can trust me when I tell you that the cost of the furnace construction was nothing compared to the values I received for my trouble.

Harold

 

[lazersteve]

Harold,

I don't have a furnace yet, but I do have a smaller tube type kiln.

I tried my first shot a cleaning the dishes with varied success. The borax did get eaten away, but not fully. The dishes are now usuable agian. I have since obtained some new ones that are not cracked and will try not to crack these by following your instructions of drying them first. I assume that by drying you mean bringing them to just over 100 C (BP for H2O) for a short period of time to remove any water in the dishes structure, correct?

Steve

 

[JHS]

Good morning Mr Harold V.
I am in the process of building a pouring furnace and would very much appreciate it ,if you could repost the pictures of the one mensioned above.The link of the furnace no longer exists.
thank you
john
P.S. I have been reading from oldest posts to the newest.
It is interesting to see where the now experts,started,and there questions.
john

 

[etack]

http://www.alloyavenue.com/vb/showthread.php?7729-Little-tilting-furnace

This is a nice one and a good forum for this.

I think this is a GRF member :wink:

Eric

 

[JHS]

Thanks Eric,
but Iam not a member of that forum,and can not access the pictures.
john

 

[etack]

Its free like this one.

Just sign up.

Eric

 

[g_axelsson]

Its free like this one.

Just sing up.

Eric

No forum would let me in if I had to sing!

:mrgreen:

Göran

 

[etack]

Its free like this one.

Just sing up.

Eric

No forum would let me in if I had to sing!

:mrgreen:

Göran

:lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol:

thats great

Eric

 

[Harold_V]

Good morning Mr Harold V.
I am in the process of building a pouring furnace and would very much appreciate it ,if you could repost the pictures of the one mensioned above.The link of the furnace no longer exists.
thank you
john

John,
Sorry to be so late posting the picture. I set this aside and it got buried.

Here's a picture of the tilting furnace. Gas fired.

Harold

 

[JHS]

Harold,
Thank You ever so much for spending the time to post the picture.
I did not think of a gear reduction for the tilt.I have the gears and chain from a old 4400
john deere combine I scraped some time back.the casters are also something I did not think of.
Looks very nice.I will head to the antique shops to find an old coffee grinder for the wheel,and that will complete
the parts list.
once again
Thank You
John

 

[Harold_V]

Unless you have a permanent location in mind, casters are almost mandatory. That furnace weighed about 700 pounds, and was not stored where it was operated, as I had another small furnace that used the same exhaust hood. It was built so it would go through the standard 36" door.

This design would lend itself to a crucible type furnace as well. Be conscious of the center of gravity in any case, as you don't want the furnace to drive when you're pouring. My target was to have a small majority of the weight below center. The large reduction in the pouring system allowed for very positive control and fine pouring. I recommend it highly.

Luck with your build. Be certain to share the results with us.

Harold