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teclu

teclu

Well-known member
Joined
May 24, 2009
Messages
180
Hello everybody!

I am new on this forum as in this domain (refining). I admit that I have red several topics on the forum, but clearly not enough. This forum is more than educational. Congrats!

Please have a look at my process which I would like to use for connectors pins. I chose this technique because I have 50 liters of nitric acid 50%. I would appreciate if you could give a few advices.

I have a few female connectors with brass pins, gold plated. Here are the pictures: http://i41.tinypic.com/2gtey8.jpg
http://i44.tinypic.com/4dfrls.jpg
I put 11,14 grams pins (100 pieces) in dilute nitric: 55,7 ml nitric 50% and 14 ml water. After four hours, when the acid stopped working, I slowly filtered the blue solution then I washed foils several time with regular water (not distillated). I put fresh acid on these washed foils, and I waited another two hours. After these two hours the acid became almost clean, so the brass was dissolved completely. I filtered the solution, I washed the foils again several times, and I left them dry. After this I saw that between them remained a white salt, here are the pictures:
http://i39.tinypic.com/20g87wh.jpg
http://i42.tinypic.com/14d0guh.jpg
What I want is to melt these foils. The question is that will this salt disappear at melting, if not, how can I get rid of it before the melting process. What is this salt? It comes from the zinc? Why doesn’t this salt dissolve in the water, it isn’t soluble in ordinary water?

Thank you for your answers in advance.

teclu
 
qst42know said:
Have you tried very hot water? Zinc nitrate should be soluble in water.
Click to expand...



qst42know,

Thank you for your quick answer. I put twice boiling water on the foils, but the salt dissolved insignificantly. You can see the foils in a hot water and salt to, here in this picture:
http://i39.tinypic.com/2hp33ywn.jpg

teclu
 
Looking at the separation in your Pyrex tray it seems like you might get decent separation in a gold pan or other gravity washing technique.
 
I would dissolve the foils in HCl-Cl or AR, filter then precipitate the gold.

Steve
 
I was do same process in early days when i start my gold refining my suggestion is first you not use mineral water because chlorine is present in mineral water which dissolve your gold with nitric acid (use distill water).........take a nylon micron mesh add distill water in your flake and white powder and filter with mesh the powder pass through the mesh and flakes on mesh .( if you use mineral water the white powder micron is 80 if you use distill water the white powder micron is under 50).........i use gasoline filtration mesh which is used in gasoline engine........this method is not good because gold recovery is 80 % and gold plating is not pure gold .it is silver and gold plating when you melt it convert it in 14 karat gold (white gold)you are beginner in refining so do it. sulfuric cell is good to removing plating items first remove pins in holder then use sulfuric cell then refine black powder in AR.
 
I would guess that the white "salt" is a byproduct of the acid and some substance in the alloy. There are a lot of different versions of brass and two substances I think could be present in some alloys is silicone and tin.
At least tin would give a white precipitate in nitric acid.

I've seen it in a number of different brass pins and my experience is that a majority gives a white precipitate in nitric.

Follow Steves advice. Just give the foils a quick wash and filter it to get rid of the copper and zinc. Then dissolve it with HCl+Cl or AR, filter to get rid of the white stuff and then precipitate the gold with for example SMB.

Good photos and a nice pile of golden pins! :D

/Göran
 
Hello everybody!

Thanks to all for the advices,I prefer to try the alcool, the mesh or other gravity washing technique first. If it won't work, I'll adopt Steve's method, even if for the beginning I wouldn't get upset for 14K.
 
Be careful to eliminate all acids with incineration prior to using alcohol. Failure to do so could cause an explosive mixture to result, in particular with nitric.
 
Steve's advice is likely the best course of action. What isn't dissolved in AR is filtered out before precipitating the gold. Testing a tiny sample is one thing but treating a large volume is another. It's an added cost and potential hazard you can do without. Zinc hydroxide was only a guess on my part.
 
teclu,

I would have to recommend Steve's advice. The time spent messing around with potentially hazardous additions of alcohol, or gravity seperation, are pretty much a waste of time.

Using HCL and clorox to dissolve the foils is easy, takes little time, and is the most widely accepted next step when refining gold foils. The reason being is that base metals may still be invloved in your foils. The precipitation of the gold from the HCL-Clorox will yield a fairly pure gold, when using SMB "Sodium Meta-Bisulfite" it selectively precipitates mostly Gold from the solution leaving most of the bad stuff in solution.

I would recommend either HCL-CL or AR, my preferred id HCL-CL for simplicity, before melting the straight foils. Once gold is melted with base metals such as copper or zinc, it is harder to refine to 24K, as it alloys with the base metals, and you a usually need to inquart to dissolve it in Nitric Acid again.

Check Steve's Website, listed under his name. He has some great videos explaining these processes in detail.

Good Luck,
Nick
 
P.S.

"Very Nice looking foils. !!!"

I also wondered, as I have read other threads which suggested Silver may be in some pins. If the white crystals are silver nitrate, I definitely would not add Alcohol. I have been warned before about Silver Fulminate as well. This substance can explode with shock.

I would recommend avoiding Alcohol for now as you do not know all the materials involved.

Nick
 
I don't think it is silver nitrate because...
1. Silver nitrate is soluble in plain water, it should just wash off in the filtering.
2. There is no reason to have silver under the gold in the contact pins.

Neither do I think it is zinc hydroxide because...
1. It is soluble in strong mineral acids as nitric acid. Any excess acid should be able to keep it in solution and it will be eliminated in the first filtering.
2. You need to add a lot of OH anions to form that much. Unless you use lye to neutralize the acid it should not form in the beginning.

Gravity separation on gold flakes isn't really possible. If it is anything like my experiments way back it will form small tubes of gold foil and the white stuff will be trapped inside the gold. The foils are too light and will just follow the water dragging some of the gold with it while smaller particles will stay with the white powder.

Go with Steve's advice, it's not that hard to do and you have to learn it anyhow. If you just melt your gold into a button you will end up with really dirty gold with unknown purity. It's better to treat it when it's in foil shape.

/Göran
 
Hello everybody! Thanks again for the usefull advices.

Meanwhile I tried with alcohol too, without result, then, after drying at low heat, I separated the bigger part from the salt (of course, a few small foils remained attached to salt on bottom of the tray). The others are here and they probably contain not more salt, than 5% of the total mass of foils.
dry female http://i44.tinypic.com/98ao58.jpg

Something interesting happened. I did the same process with male connectors too, to compare the results… pictures are here
http://i41.tinypic.com/2hi8df4.jpg
http://i39.tinypic.com/138zm90.jpg
http://i44.tinypic.com/2ow17wg.jpg


I was surprised to see, that after dissolving 100 pieces of pins in nitric, salt didn't result. Here are the male’s foils in water
http://i43.tinypic.com/11jlsoo.jpg

and here already dry
dry male http://i39.tinypic.com/2h96war.jpg

The manufacturer of the connectors is one and the same for male and female, and the brass is an alloy with Cu70% and Zn30% , without other metals, Ni layer is under gold, the connectors are NOS, produced in 1985.

Results:

male:
100 pins... 16,8 g
dry foils... 160 mg
1,6 mg foils/male pin or aprox. 1% from total weight of pins
female:
100 pins… 11,14 g
dry foils… 270 mg
2,7 mg foils/female pin or aprox. 2,5% from total weight of pins

What do you think about this?

I believe that HC-CL is too much for my knowledge for the beginning, but after I’ll take out all the foils, and with the things I'll learn from you, it is very possible for me to take the next steps.


teclu
 
aurumshin said:
congratulation! teclu you achieve your target.
Click to expand...

aurumshin, thanks for the incouragement, it is very refreshing at this point; let us not forget, that "gold is gold but real gold is knowledge".
 
teclu said:
The manufacturer of the connectors is one and the same for male and female, and the brass is an alloy with Cu70% and Zn30% , without other metals, Ni layer is under gold, the connectors are NOS, produced in 1985.
Click to expand...

Obviously the composition of the male and the female parts differ. I would guess there is some additions to the female parts as they need to be more springy and flexible.

I really like the nice pile of golden pins.
You have some good stuff there.

/Göran
 

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