I have about 150g of silver contacts trimmed with a little copper left. I mixed about 300ml ~12% HCL and 100ml 3% H2O2 and added maybe 10g of the copper I trimmed from the contacts, just to try and get the solution going but it wasn't going green so I added all the contacts(non-magnetic) and it started turning green. Came back maybe 20 minutes later and there was a black haze/cloud around the contacts at the bottom of the solution. What could this be? I believe I have added far too much HCL and H2O2 for the amount of contacts present, is it possible it is silver chloride? I gave the glass a swirl and it disappeared.
Black cloud in AP
- Thread starter brockles
- Start date
Help Support Gold Refining Forum:
Probably saturated Copper Chloride.
So can I just keep on adding HCL until all the solid copper has dissolved and the black cloud no longer precipitates? I had read that copper would precipicate out white?
Thanks
Martijn
Well-known member
Add an air bubbler. Only add HCl when you get white precipitate on the bottom or when the solution turns darker.
Martijn
Well-known member
Copper 1 chloride.
The brown is not a precipitate, it is concentrated so adding either Oxygen or fresh HCl will fix it.
Are you using an air bubbler?
It may be faster, since all reactions are faster in the heat.
It will also evaporate faster, so one needs to keep an eye on it so it do not dry out.
Martijn
Well-known member
This is a picture from one of our members.
Golddigger76
Well-known member
I don't believe that your solution could have been saturated in 20 minutes .
Golddigger76
Well-known member
Sorry but I got distracted and couldn't finish what I wanted to say and ask, but was there any solder on the contracts or was some of them coated with black soot from arching- failure ?
If you reread the post, you will see it formed under stagnant conditions, and disappeared when stirred.
Some of them were silver soldered to the little fingers. Some may have contained remnants of arcing but would that just be oxides of metals the contacts contain?
Over the past couple of days I have been adding bits of HCL and today I noticed some of the copper remains of the fingers(I did clip them as close to the contacts as possible) were a grey colour, similar to the colour of the silver contacts after being in the solution for a while but when rubbed, the grey material would wipe off/come off in flakes, exposing the copper underneath. Is this silver chloride precipitated out onto the copper?
Most likely Tin
Would this be metallic tin or tin chloride? If metallic, can it just be removed with NaOH or HCL? If tin chloride, removed with water?
When it dissolves in HCl it becomes Tin Chloride.
It is probably Tin metal that cements out on the fingers.
In thery it should not happen, but in the real world it does sometimes.
I also have some magnetic contacts and rather than removing the base metals with HCL, I had some old chemicals laying around that I was going to throw out anyway so decided to add them to the contacts to see if they would remove any of the base metals. I added citric acid powder, acetic acid in the form of distilled white vinegar and some rock salt. The first photo is maybe an hour or two after adding it all and the second photo is two hours after the first one. Originally, all the contacts were silver coloured and all but a few are now copper coloured. Everything has turned a more copper colour. If I was to guess, totally uneducated but the oxides on the copper/base metals have been removed and then precipitated copper onto the silver contacts?
Attachments
Copper do not cement on Silver, it is the other way around.
On the other hand Copper Cements on Iron.
Why are you doing this, you have no Idea what kind of toxic concoction you are making.
How do you know if there is any Silver there?
The moment you added Salt you have stopped any dissolving of Silver.
Point taken, I will stick to conventional methods that are well known, tested and trusted.
I saw something on YouTube I think it was where they did something similar with citric acid and salt.
As far as I'm aware, silver contacts don't ordinarily have iron in them(I maybe wrong), there would be no reason for copper to cement on them so unsure what has happened here.
I saw something on YouTube I think it was where they did something similar with citric acid and salt.
As far as I'm aware, silver contacts don't ordinarily have iron in them(I maybe wrong), there would be no reason for copper to cement on them so unsure what has happened here.
