I need a little clarification

[butcher]

From what I understand the gold would have to have been already dissolved as a chloride, (as an ion, missing electron), for the hydroxide to form the sodium aurate, elemental gold metal is very resistant to oxidation, I believe even very thin gold would not oxidize easily.

This is some of what I have read:

Gold dissolved in solutions of AuCl3 react with strong base NaOH and will precipitate gold hydroxide Au (OH) 3, .which can dissolve if excess NaOH is used, and apparently this will form sodium aurate (NaAuO2). If gently heated, Au (OH) 3 decomposes to an oxide of gold Au2O3, more heat then to gold metal.

click here

 

[Geo]

so you can compound gold to almost any base by dissolving gold in AR and then adding the base thereby forming the salt of that base compounded with gold, Aurate.so if gold can be a sulfide in solution does that mean that im loosing gold in my stock pot unless i condense and incinerate everything in the pot?

 

[artart47]

Hay guys! happy thanksgiving and thanks for all your interest in this riddle!
I think you are right in that our gold is as unrecognizable powder, I kept everything and after thinking over you advise, I'll find it. I'll make sure to post whatever the results are. I am taking your idea about not removing the mask and exposing the copper. only some boards had gold under the mask.
Thanks again

 

[butcher]

Geo,
"So you can compound gold to almost any base by dissolving gold in AR and then adding the base thereby forming the salt of that base compounded with gold, Aurate. So if gold can be a sulfide in solution does that mean that I am loosing gold in my stock pot unless i condense and incinerate everything in the pot?"

I do not know if I can answer your question, but until I get more education here is how I see this:
say I have a base metal dissolved in solution (lets say HCl), and now I add sodium hydroxide, at a certain point the solution looses its acid and the base metal will begin to precipitate, the very reactive sodium (metal) from the sodium hydroxide solution will join with the chloride from our acid (or dissolved base metal) and make table salt (NaCL) this salt is fairly soluble in solution, now the OH (hydroxide) will join with free hydrogen and form some water, and OH will also help to make oxides or hydroxide of our base metals the precipitant in the bottom of our bucket, now if I add a large amount of hydroxide (large excess NaOH) then I can form complexes that again will make our base metal soluble, (gold and silver included can form soluble hydroxides if conditions are right). Now do you use a pH meter?

I do not think you need to worry about a healthy stock pot, and the gold being soluble, and you have your stannous chloride if needed.

 

[Geo]

i use test strips from pool supply.

 

[butcher]

My pool supply also has pH indicator solutions, these will work where the solutions are not colored strongly by metals.

I was curious about the chlorine tests strips they sell have you tried them?

 

[Geo]

no. i just have strips to test PH.

 

[g_axelsson]

This is an old thread but I wanted to add one possibility to why it looks like lye is dissolving gold.

Funny you should ask. the lye did lighten the color somewhat.

A couple of years ago I did try to remove solder mask from fully plated boards (old HP boards) but after a while in lye some of the gold fingers turned white. The gold wasn't dissolved, it was a white metal that had plated on top of the gold.

My theory (I haven't tested it yet) is that led is dissolving in strong lye. Then the weak solution with lead plates out on another surface which is in contact with a less noble metal, tin for example. So when tin is oxidized the lead plates out on top of the gold.

If lye would dissolve the base metal under the thin gold we should expose pure copper, not a lighter color track.

My cards were cut down in small pieces so not all fingers had contact with solder and only a couple of the fingers got plated. The later AP process removed the copper and left the gold as usual.

As a footnote I think Silver Handle got a bad advice, as I read the thread he had used AP and got the advice to drop the gold from the AP with SMB. He probably had the gold as a fine sediment in the bottom already and it wasn't dissolved. Adding SMB to that probably just created a mess. The one giving the advice probably thought he had already dissolved the gold.
I hope he got his gold in the end.

Göran