Odd precipitate in solution from dissolving gold pins from computer scrap

I have a pile of computer scrap that has hundred's of thousands of gold pins and I thought I would try a small sample of a few pins and try a couple methods of dissolving the pins leaving the gold behind. The pins I have are the kind from old IDE & SCSI connections and some CAT5 jacks (female). Some were impossible to remove from the plastic so I chopped up the connector and threw the plastic in with everything else and it's incredible that there is basically zero damage to any of the plastic.

I've been told that the pins might be a phosphor bronze, they don't seem like copper though they may have some plating. There also was a very small amount of solder on the pins (maybe 1-2% which could be Sn/Ag or Pb/Sn I'm guessing).

I used 31% HCl & 35% H2O2 with some distilled water and a little heat to begin. When adding the HCl it started to turn yellow pretty quickly and when the H2O2 was added a green color appeared until it was done dissolving. When things seemed finished (IDK if it was b/c the acid was used up or all metal was dissolved) but the solution turned from green to blue like a light copper sulfate color and I started getting a grey and light blue precipitate very similar to what is in the pictures but what is green in the pics was blue. I added a little more HCl (about 5ml - or an additional ~15%) and the solution quickly turned back to green. After that I've allowed it to sit for about a week at room temperature and the result is what is in the pictures below.

There seems to be 3 layers of precipitate. A white one on the very bottom, a grey "fluffy" layer above that and then the light green layer on the top which is the stuff that had been blue before the additional HCl was added.

When I added the 5ml HCl I mixed everything up again and it seemed like everything dissolved again into solution. I may have added a little more H2O2 as well.

So I'm trying to figure out what these three layers might be as per chloride salts.

Also, the top view shows a layer of film that keeps growing which sinks and forms the top green layer. I didn't see this happen when the grey precipitate appeared, I think that happened fairly quickly compared to the top green layer.

Is the solution pulling CO2 out of the air allowing a copper (complex?) to precipitate? Can anyone identify any of the other possible precipitates?

Quote: Originally posted by Sulaiman

AFAIK HCl + H2O2 can dissolve gold ! I don't know what other metals you have but copper, nickel, iron, tin and lead seem common, none of which are worth recovering - in my opinion. There is (usually) very little gold on connectors, opinions will vary but I suggest HCl first, be patient and aggitate the mixture daily. Decant the liqid to waste disposal. Rinse thoroughly several times to remove HCl, Dissolve away the remaining base metals with dil. HNO3 You should be left with mainly gold, dissolve in Aqua Regia, (do not add excess nitric acid) filter, add a few drops of H2SO4 to precipitate any lead, filter, drop the gold out of solution using your favourite reducer (SMB etc.) then be dismayed at the yield vs. reactants, time, waste disposal and general mess involved. (I still have one small bottle of black/grey/fluffy sediment in liquid blue/green waste to deal with) kadriver aka sreetips@YT videos cover almost everything involved.

First thing to do is to make or buy some Tin(II)Chloride solution.
You really must be able to detect gold ions
(or more importantly, be sure of the lack of gold ions - test your test solution.)
Every time a process produces more than one liquid,
test each with SnCl₂ before discarding any

So far I've not managed to make gold disappear, only change character,
its always in there somewhere no matter what dumb things I tried earlier.

Also, gold is so dense that it settles really quickly,
so waiting for precipitation then decanting wastes almost no gold,
whereas filtering always requires further recovery operations.

P.S. my entire hoard of gold powder is 2.7g, over 1g of which was from jewelry,
so my experience is rather limited - so treat my advice accordingly.

[Edited on 23-4-2019 by Sulaiman]

Quote: Originally posted by Sulaiman

First thing to do is to make or buy some Tin(II)Chloride solution. You really must be able to detect gold ions (or more importantly, be sure of the lack of gold ions - test your test solution.) Every time a process produces more than one liquid, test each with SnCl2 before discarding any So far I've not managed to make gold disappear, only change character, its always in there somewhere no matter what dumb things I tried earlier. Also, gold is so dense that it settles really quickly, so waiting for precipitation then decanting wastes almost no gold, whereas filtering always requires further recovery operations. P.S. my entire hoard of gold powder is 2.7g, over 1g of which was from jewelry, so my experience is rather limited - so treat my advice accordingly. [Edited on 23-4-2019 by Sulaiman]