white/greyish salt?? excess nitric?

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zichuan

Member
Joined
Jan 22, 2013
Messages
6
Hi all,

I am new to refining. Would be glad someone could enlighten me. My project is gold pins from various motherboards, ide pins, etc..

I encountered problems during first step of removing the base metals using technical grade nitric acid 68%.

I do not know whats the problem, it seems taking me quite a long time to removing all base metals using boiling methods.

I suspect i mis calculate the 50/50 rule, and end up using more nitric then water. Nevertheless i experience myself to just continue boiling method, till the solution is quite thick. But after stiring, i see that those pins has became brownish without gold anymore. But it just couldnt eat away those metals. I gave up. I put it aside and filter away the pins and gold sands. After filtering by keep adding water till the gold sand settles. I found that quite a large sum of whitish/greyish powder or salt mixing togethe with the gold sands.

Now my question is, is it the problem of excess nitric? Or...? I missing a step?

Please kindly advise! Thanks alot!
 
photos are always welcome
and you may have a big tin mess on your hands, i would say read, read and read some more
 
My photo are not very sharp. But you could figure it out.
 

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A better picture of the cream looking greenish. Is it tin?

Can i use hcl to disslove it under boiling method?
 
zichuan,

It is good you have some understanding what you are doing. However, each base metal requires particular chemical to be dealt with. Nitric Acid is good at removing Copper and Silver. HCl is good to remove Iron and Tin. H2SO4 is good to remove iron and aluminum. If your pins are of different metal composition you have to consider using HNO3 or HCl to be the last treatment as you will have to mix both acids to produce Aqua Regia to dissolve gold. Or you would have to go through incineration process to not loose little gold those pins have.

If your pins turn brown, I would assume they had very little gold plating on them. However, normally gold foils float on top. I would suspect the pins are from Pentium 4 processors, which makes no monetary sense to process.
 
What I have found, when doing these type of pins, it is best to use AP process. I put my pins in a mild solution of H2S04 first to remove any PB (lead) let is set over night, decant, wash well with boiling hot water several times to remove the lead, then use the AP, two parts HCL to one part H202 after the reaction starts and slow down I add air - bubbling the solution - leave it alone until all the pins have digested and only foils are left. The copper chloride II will dissolve the base metals. Do not get in a hurry, this can take several weeks to do depending on how much there is. From my experience it takes about ten to fourteen days for one ounce of pins to completely digest. Then decant the AP through a charman plug and reuse the AP on another batch.

It works fairly well for me, hope this helps.
Ken

edited; for correction SN to PB
 
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