Rolling out Gold

[PhillipJ]

Here is a picture of a 5 gram button I rolled out

It is one of the 1st buttons that I made, so it's quality was questionable. It was quite shiny to begin with, but I had my doubts as to it's purity as it was before using Harold's cleaning method.

It seemed to roll out pretty good. I didn't flatten it out before rolling. Just put the whole button in & rolled back & forth. It is now .005" thick.

The sheet seems fairly flexable. My concerns are the crack on the edge and the bumpyness in the middle. Also it now looks like brass shim stock in color. The rolls may have been a little dirty.

Any comments from some of our more experienced refiners would be appreciated.

Thanks for looking

 

[lazersteve]

Phillip,

Your right about the questionable purity, the color is not what I would expect (even considering camera color variations) to see from pure gold. If it were my button it would inquart it with 15 grams of silver. Then I would hit it with some nitric, followed by a dissolving stage and SMB precipitation.

Steve

 

[PhillipJ]

Thanks Steve.

You made me laugh. Ya. It does look pretty bad in the picture. It looks a little better after I cleaned it with some thinner. The rolls were a little oily I guess.

I think I'll use it to help drive the nitric out of AR before evaporating.

I don't understand why you would inquart it though?

 

[lazersteve]

Phillip,

You would inquart to remove the impurities. Assuming it's higher than 10kt (I'm pretty sure it is) you need to add 3x it's weight in silver to assist the nitric in dissolving the impurities out. If you don't inquart, the gold will shield the impurities from the nitric and they won't dissolve into the solution. For the purpose you named (using up the remaining HNO3 in AR) it will do fine except that you will be adding more impurities to your AR solution and thereby have more drag down garbage. If you just want to purify the 5 grams you should inquart.

Steve

 

[Harold_V]

Phillip,

You would inquart to remove the impurities.

Not in this case. assuming the gold is not contaminated by a high percentage of silver (less than 10%).

Because it borders on being pure, a simple dissolve in AR and re-precipitation would be a better choice. Inquartation is used because of a preexisting abundance of silver, which prevents AR from dissolving gold. Truth be known, white gold can be directly dissolved in AR without inquartation, as could some of the other gold alloys. The determining factor is the percentage of silver in the base alloy, and white gold contains no silver.

By inquarting, it's entirely possible you'll introduce more contamination than is currently present. The ideal situation is to re-dissolve the washed gold before it's melted, while it's finely divided and dissolves easily. Rolling the melted gold thin is the next best option, and you benefit by having some of the contaminants removed in the melting process, so in its own right, it can be the better of the two processes if you discount the added labor.

Do not construe that processing all alloys isn't best accomplished by inquartation. You benefit even by processing white gold that way, and I recommend it be done by that method. What that does for you is allow the base metals to be removed to a very low level before dissolving the gold. Makes for a cleaner end product.

Hope this helps clarify the point at hand-------when to inquart.

Harold

Edit: deleted repeated word, with no change of information.
Second edit: changed the word the from the word to to correct a typo.

 

[Harold_V]

Here is a picture of a 5 gram button I rolled out

The sheet seems fairly flexable. My concerns are the crack on the edge and the bumpyness in the middle. Also it now looks like brass shim stock in color.

That it rolled that thin is a testament to the quality of the gold, although it may not reflect how pure it is. If the gold was contaminated with the wrong elements (lead being the worst offender), it would have cracked (it's called alligatoring, for obvious reasons), instead of rolling. It would have the same tendency if the gold was contaminated with oxides of base metals, although to a lesser degree.

If you want to improve the appearance of the rolled gold, give it a light boil in dilute sulfuric acid. Rinse well afterwards, needless to say.

It could be alloyed with traces of malleable elements that are compatible with gold (copper and silver) and still roll with good results. It is for that reason that I say that it is not a measure of the purity.

Any comments from some of our more experienced refiners would be appreciated.

You can avoid the wrinkling and distortion by annealing the gold between passes. Anneal it at least one time, if not more. It isn't necessary to anneal between each pass, although that is the best of all worlds. Otherwise, each pass through the rolls will make it harder and harder, until it will refuse to roll further with the pressure and power available. It will often crack under that condition instead of roll thinner.

Annealing returns the metal to a dead soft condition. You'll have to experience this phenomenon to understand the difference. Anneal it even if you think it isn't necessary, in other words.

Heat the gold to dull redness, then quench it if you desire. It can be left to air cool just as well, although, if, when it's heated, the gold oxidizes to some degree, quenching in water will help limit and remove the oxide coating.

If your gold is pure, it will not change color upon heating, and will be just as bright after annealing as was before. If the gold is pure, it will be so soft after the annealing process that it can't support its own weight when the sheet is held flat-wise. If you intend to use this gold as an anode for plating, I suggest it be refined a second time.

Clean your rolls well before rolling.

Thanks for looking

Thanks for sharing!

Harold

A side note to Phillip. I have made my own electrolyte for gold plating, and have used it with success. I'll provide more information as time allows, via PM, as promised. It's not beyond your ability to make your own.

 

[lazersteve]

Harold,

With your previous post in mind, at what karat is inquarting recommended? Is there a range of karats at which one should inquart? If the source gold is between 14-18 kt?

Thank you for setting me straight Harold.


Steve

 

[lazersteve]

I have made my own electrolyte for gold plating, and have used it with success. I'll provide more information as time allows, via PM, as promised. It's not beyond your ability to make your own.

I'm interested in this also, please PM me as well.

Good Stuff Harold, as usual!

Steve

 

[Harold_V]

With your previous post in mind, at what karat is inquarting recommended? Is there a range of karats at which one should inquart? If the source gold is between 14-18 kt?

My policy was to inquart everything. It, for me, was the easiest course to pursue, and insured that my gold chloride solution was quite clean. That was a concern to me, even though I had a policy of re-refining my gold. Regardless of the number of times you refine, the cleaner the material is for each cycle, the cleaner will be your results. In my opinion, the inquartation step is not negotiable.

I don't know that you can isolate this by karat fineness. The color of the alloy is a far better indicator than anything else. Green gold, for instance, is very high in silver. It's the silver that makes it green, believe it or not. It stands to reason that no level of karat gold that is green will endure a simple digest in AR----not without taking extraordinary steps to produce a huge surface area with a thin cross section.

As I mentioned, some of the alloys don't really need inquarting, but you benefit greatly by doing so. Based on that, I'd suggest that all karat gold be inquarted. If it does nothing else, it insures that you won't have the same problem Paige had recently.

If you care to look at the alternate, any alloy that is lower than 10% silver should digest in AR, although it may yield problems as the percentage approaches the high end. Thin material can be the solution, for it is dissolved totally before the hard crust of silver chloride can form well enough to isolate the gold from the AR. In that case, even if the silver chloride tends to accumulate as a thick scale, once the gold is digested, the tendency is for the silver chloride to reduce to the familiar flocculent form you see routinely.

I still recommend inquartation----always. Only when the gold content is greater than 90% would I not. In that case, it is usually easier to dissolve and expect a second refining to improve quality because of the relatively high level of trace elements that are included in the chloride solution. YMMV.

Harold

 

[Harold_V]

I have made my own electrolyte for gold plating, and have used it with success. I'll provide more information as time allows, via PM, as promised. It's not beyond your ability to make your own.

I'm interested in this also, please PM me as well.

Good Stuff Harold, as usual!

Steve

Thanks.

If I can get things together tonight, I'll try to take a pic of some gold I used for the anode in my one and only gold plating experience. I still have it, along with the electrolyte I made years ago. I'll try to post that, and a picture of various palladium salts, examples of which I still have in small sample containers.

Unfortunately, the technical information for making the electrolyte isn't available to me at the moment. I recall how it was done, however. Gold chloride is evaporated to eliminate acid, then it is dissolved in sodium or potassium cyanide solution. The solution is almost dead clear, with but a hint of straw color. Sorry, without access to my refining books, I am unable to provide more detail. I don't know that I even made notes. I'm not anywhere nearly as organized as you appear to be, and kept almost no records. I did almost everything from memory----with the odd look at Hokes' book when I was puzzled by something.

Couple that with the fact that it's been more than 13 years since I last wore my gloves, I am having a little difficulty remembering some of the details on these processes. I hope to eventually locate my books in our storage area, so more information may not be forthcoming in the immediate future.

Harold

 

[aflacglobal]

Harold. You telling me you haven't refined in 13 years. Dam, i guess things do get fuzzy. I would have to read everyday just to keep up. :lol:

If you care to look at the alternate, any alloy that is lower than 10% silver should digest in AR, although it may yield problems as the percentage approaches the high end. Thin material can be the solution, for it is dissolved totally before the hard crust of silver chloride can form well enough to isolate the gold from the AR. In that case, even if the silver chloride tends to accumulate as a thick scale, once the gold is digested, the tendency is for the silver chloride to reduce to the familiar flocculent form you see routinely.

I was having a discussion with someone the other day about a mine issue. Sort of. My question is this: If i took gold that had been run thru an atomizer. It's like shoting but produces fine powder instead of flakes or shot. Then took the fine powder and introduced it to AR. Say the gold was 75 gold and 25 % silver. Now the point i am trying to make i guess is that since the gold is so small would it tolerate the silver. I was wondering if the gold would dissolve leaving the crust to collapse in on it's self. It seems that if the particles were small enough that the crust could not form a thick enough skin to stop penetration, even if by some wicking effect thru the crust i would think that it could still penetrate the skin. Sort of like the surface tension of a bubble i guess :?:

Is it possible Harold ?

 

[Harold_V]

Indeed it is, assuming the particles are fine enough, and you have nothing but metals, no gangue included.

If you're dealing with ores, you'd most likely have far better success with cyanide, especially if the material was reduced in size to miniscule particles, and contained no cyanicides. A sulfide ore does not lend itself to the process nearly as well as an oxidized ore.

Cyanide will dissolve both gold and silver, and leave behind base metals, assuming you use a dilute cyanide solution. As I recall, if you keep the percentage down around .02%, it's selective. Maybe GSP can chime in here----my ore experiences go back earlier than '83, and my memory has dimmed considerably.

Assuming no cyanicides, cyanide is consumed only by dissolution of values. It is very economical to use, and does a great job. Recovering the values from the pregnant solution can be as simple as introducing zinc flower. They can also be extracted with a carbon pile, or by electrowinning.

By sharp contrast, the idea of separating values from ores with acids isn't generally a good one either. Acid reacts with many of the elements commonly found in ores, so it is often wasted doing no work. Cost of extraction can be extreme due to wasting the acid.

If you're interested in this field of conversation, I would encourage you to study Rose's book. He was considering a leading authority on gold a century ago. Book is titled The Metallurgy of Gold. I has been printed several times---there's at least seven editions. I have a photo copy of the sixth. From it I managed to learn to process a gold telluride ore, plus gained enough information to successfully build the ball mill I used to process the ore.

This issue is far more complex that you've made it, or at least it can be. Depending on the nature of the ore, there may be cyanicides present that destroy the cyanide-----or the ore could be a complex that won't dissolve in cyanide without being oxidized. A careful study of the ore in question would be important before making any decisions regards a preferred process. Jumping in blindly could prove to be a serious economical mistake.

Harold

 

[Harold_V]

As promised, this is a picture of gold that I refined, melted and rolled for use as an anode for gold plating.

I plated two railroad spikes, one for a now deceased friend, and I retained the other, which I still have. One of my customers had a nickel tank so I bead blasted the spike until it was free of scale, then had him plate the spike with nickel, to act as a barrier. I didn't want either of them to have a high luster, so there was no polishing involved. If anyone is interested, I could post a picture of the spike.

No, Noxx, you can't have it to strip! :lol:

The anode pictured weighs roughly 1-3/4 troy ounces. If you look carefully, you can see the immersion depth. The anode was placed in the cell with one edge exposed, so that portion was unaffected by the plating process.

Harold

 

[goldsilverpro]

Harold, you sure do good pictures!

Every time you post one, I kick my own butt for not taking photos over the years. One I wish I had taken, in 1970, was my 6 year old son sitting on $1,000,000 worth of 400 oz gold bars (27# each - 60 bars total - 1600+ pounds) - at $42 per ounce. It was in transit and was parked in our safe for a couple of days.