Black cloud in AP

[brockles]

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.

 

[Yggdrasil]

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.

Probably saturated Copper Chloride.

 

[brockles]

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]

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

Add an air bubbler. Only add HCl when you get white precipitate on the bottom or when the solution turns darker.

 

[brockles]

Add an air bubbler. Only add HCl when you get white precipitate on the bottom or when the solution turns darker.

Will do. What do you suspect the black cloud to be?

Many thanks

 

[Martijn]

Copper 1 chloride.

 

[Yggdrasil]

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

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?

 

[brockles]

I have now added an airbubbler so hopefully that will keep the whole thing moving. Is it worth putting out in the sun or will this not achieve too much?

 

[Yggdrasil]

I have now added an airbubbler so hopefully that will keep the whole thing moving. Is it worth putting out in the sun or will this not achieve too much?

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]

This is a picture from one of our members.

 

[Golddigger76]

I don't believe that your solution could have been saturated in 20 minutes .

 

[Golddigger76]

I don't believe that your solution could have been saturated in 20 minutes .

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 ?

 

[Yggdrasil]

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.