Solubility of Gold in AP

[warrendya]

Steve's General Reactions List states that hot AP will dissolve gold. How hot is hot? I ask because I just poured off the AP from some foils, and there was still quite a bit of tiny pin pieces mixed in. I added some fresh AP thinking it would clean them up and within 2 minutes everything had dissolved. I live in the Mojave desert and the garage and chemicals were probably in the mid-90's Farenheit. Should that have happened?

 

[Oz]

It can be a trade-off as to speed vs. dissolving base metals only. I have had 60*F AP dissolve some gold. The more H2O2 the faster the reaction, added heat also speeds reactions. I don’t usually add extra H2O2 as I am not usually in a hurry, if fact I often leave things in longer than needed and dissolve some gold that way. I don’t see it as a problem as the gold is still in solution.

 

[Wyndham]

Oz, if there is some gold dissolved into the ap, after filtering, is there a better reducing agent to get the gold that maybe in with the base metals. Is this where copper metal will replace the gold in solution and percipt out? Will it also bring out other metals as well? Thanks Wyndham

 

[Oz]

Wyndham,

Copper will indeed replace any metals that are more noble in your AP solution. The copper will turn the solution almost black when it is saturated. If you are not in a hurry for your gold you could also keep using your solution until it becomes saturated by copper accomplishing the same thing but getting more use out of it.

 

[Platdigger]

Only those metals higher in the electromotive series than copper, will be displaced by copper.

Silver
Palladium
Mercury
Platinum
Gold

To name a few.

Not base metals.
I believe the "entire" platinum group also, would be included in this list.

In other words, metals more "nobel" than opper.
Less chemically (or electrically) active.
Randy