nitric and gold filled question

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wood4lif

Active member
Joined
Apr 7, 2012
Messages
43
i just processed my first batch of gold filled pocket watches. the question i have is are there any values in the large amount of purple/brown powder that is with the gold foils?...and im assuming there must be gold in solution because of all the purple stains on my rags ,fingers etc. is that normal?...im going to make up some stannous chloride right now just to be sure....just wanted to know if evrything i mentioned sounds normal . thanks
 
wood4lif said:
the question i have is are there any values in the large amount of purple/brown powder that is with the gold foils?...
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Could be. You most likely have sivler chloride and or colloidal gold. Don't throw anything away.


Geo said:
the purple stains sounds like silver.silver is present in gold filled.
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Gold chloride can also make the same exact purple stains.
 
The purple powder may be tin.

Gold filled does contain silver, but it all should have dissolved and be in solution. Silver nitrate stains skin purple, hence the purple stains on your fingers.

Filter the solution and save it for silver recovery. You can do that by cementing or the silver chloride method, whichever you like.

The solids will have the gold and probably some tin if you have purple residue.
 
Westerngs said:
Gold filled does contain silver, but it all should have dissolved and be in solution. Silver nitrate stains skin purple, hence the purple stains on your fingers.
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This is true. Re-reading this post from the beginning I see that I overlooked the fact that this "mud" was together with the foils. I thought he had gotten through the AR stage. If all that’s been used so far is nitric then the purple stains are indeed from gold filled silver pieces. This doesn't totally rule out silver chloride however. You can get AgCl throughout the entire process.

1. If you use tap water in the nitric stage small amounts of chloride can form because of chlorine in the water.

2. Remember that gold filled is a thin sheet of karated gold. You will get silver chloride at the AR stage and there is no avoiding it.

3. Your gold chloride can have small amounts of silver in it from AR digestion. This is why it’s advised to dilute your solution prior to filtration. There's nothing more annoying than getting a picture perfect filtration and then silver chloride dropping out when you add water.
 
silver chloride turns metalic grey in bright light. silver nitrate is a clear liquid that makes a purple to black stain in bright light, thats why you may not notice the stains until the next day if your working at night.
 
purple? really? dang, subtlety in these shades is a real problem for me.its hard for me to tell the difference between green and blue sometimes unless its a real deep color.
 
It seems like you were asking your question at the stage in your process where you have just completed Nitric Digestion of all other metals except lead and gold? If you have gold foil in the leftover material that didn't go into solution, is that right? You might not have used enough Nitric Acid to consume all the metals it could. That material could be anything that was included in the rolled/alloyed metal you put into the nitric to begin with. And if this is not at that stage, but after AR, then you didn't use enough AR to fully digest the gold into solution, you wouldn't have foils if you did. If this IS right after the nitric reaction, and before AR, then it shouldn't have any gold in solution at all, nitric acid reacts with gold, but it doesn't consume gold, but it's good to check just in case something else is going on that you haven't figured out yet.

I might have misunderstood you though, I am trying to follow the thread and comment on points not mentioned yet, but if I am wrong, as usual, someone please call me on it.

You mentioned you were using shop towels, are they colored shop towels? Like red? Because anytime those come into contact with NOx, gas, or certain acids, they turn a deep purple color. I use them so I can tell easily what is contaminated or not, not that I rely on it but it's shocking how discolored one will get, when you thought it was clean. I got the idea from a special tape I used when I made the nicoderm patch for Johson&Johson. We had to wear fully enclosed, silver lined positive air flow suits because one drop on pure liquid nicotine on your bare skin would send you to the hospital, and could kill you. For all the zipper joints, and wrists etc, this blue tape was used so that if you got nicotine on your suit, it would discolor and you would know you had to wash that area down real good before taking your suit off. It's possible that if you are using shop towels that they are reacting with whatever chemicals you are using at the time, and that those colors you are seeing have nothing to do with anything that is in the solution.
 
yes i just finished digesting around a 100 grams of gold filled in nitric. from what ive been reading on this forum getting rid of as much base metals as possible is the better way to go before putting it into solution of AR.
..... i pulled all the large foils out the solution and rinsed. then i poured my digested nitric solution through a filter to catch all the fine gold. but i did it twice. the first filter was very brown/gold ( i put that aside) then i ran the solution again through another filter and that contained all grey and purple mud which im sure must have also been in the first filter too but just un noticed due to the larger brown and gold mud. ..
to be more clear, i guess my question was should i disolve what i have in the first filter in hcl/cl to seperate the silver and whatever eles that may be mixed within, and run the heavier larger foils through AR seperatly.
just to note, all the G.F. stock i used was 25 & 30 year pocket watch case. also to note, and it may be premature to state this, but it seems to me these cases may hold 3-5 grams of Au in each.
 
i just read your post again and your right. thats what i didnt do was dilute prior to filtration and i did use tap water to rinse...i see how it would have have made a difference..but i only used the tap water to rinse the larger foils..oh, but i diluted my nitric with tap water. ok
 
I would incinerate the filter and powders, red hot, cool, cover in HCl bring to boil, lower the heat but keep the solution hot, add a little water let it continue to heat, let powders settle well, use suction bulb to remove liquid to a settling jar (powders formed in this jar are also saved in stock-pot for later processing), several more rinse's with hot water, until washes clear, the Hot HCl and water washes may need repeated depending on base metal content.

The incineration helps to oxidize base metals (and tin), the HCL will remove tin oxides, and other base metal oxides, and the hot water will help to remove lead chlorides.

This will help to remove some of the base metals your nitric left behind.
 
thanks for your input guys and il do that with batch #1 ...i also just started another batch but this one im using sodium nitrate instead of nitric 70%. boy what a difference....
i put in 8oz of sodium nitrate to boiling 480ml water, added it to 120 grams of G.F. ( last night) when i came home from work today to see how it went and the only thing that has changed was an addition of a brown sediment all over the undigested metal and on the botttom of my flask. 0 digestion , not even a color change in the solutuion. so my guess is that heat is an added requirment when using sodium nitrate compared to a diluted 70% nitric.
yes?..and do you have any ideas on what the brown sediment is and where it came from and why?
 
wood4lif said:
i put in 8oz of sodium nitrate to boiling 480ml water
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If you used sodium nitrate and boiling water you have a solution of sodium nitrate not nitric acid, (if you had used sulphuric acid and sodium nitrate you would have poor mans nitric acid) so heating isn't going to make a whole lot of difference.
 
thanks... i think i should also get me a pair of reading glasses too. seems like i missed a few simple but important steps...thanks again
 

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