nitric acid bath for gold

[Anonymous]

supposedly nitric acid will dissolve all metals except gold. i have a receipt for a nitric acid bath of about 70% which i followed exactly as the directions stated. placed some plated jewelry in bath, saw the gold separating and some floating reaction causing bubbling and the other metals dissolved. very excited then i noticed gold was also gone! set this one a side for the moment , tried another with the same result, the acid turned pale blue in the first, greenish-blue in the second one. tried a 3rd time with gold filled (checked and verified) gold started to drop and suddenly disappeared. this acid a very bright blue. all three have varying degree of white salt settlement. what is happening? help please!
huelo the surveyor

 

[lazersteve]

Sounds like the gold may have broken down to a fine brown powder or possibly you had some chlorine in the mix that dissolved the gold.

I can't see residual chlorine (from tap water) dissolving all of your gold unless you only dissolved a very small amount of scrap.

Can you give us some more specific details on the reaction conditions (ie source of material, dilution, quantities, etc.)

Steve

 

[nicknitro]

Don't rule out possibly the scrap wasn't gold at all.
LOL. Lotta copper from the sounds, maybe it was brass to begin with. Steve, would the zinc salt out as white crystals?

Why do you use 70% nitric anyways? Usually most people dilute their 70% nitric with distilled water to help catch some of the NO2 fumes and increase the efficientcy of the nitric acid. Increased molarity would probably be wasteful, violent, and create a lot of heat/fumes.

I think Steve, said it best though, "More Info Please".

Good Luck,
Nick

 

[Anonymous]

one bath was with plated gold, 14k gold ring, second bath with mostly plated due to not wanting to loose anymore gold.
third was an individual pocket-watch chain gold filled checked and verified. each of the baths have white crystals in them, with the most being in the last one with only one object the pocket-watch chain. the nitric acid mix is as follows:1quart sodium nitrate mixed with aprox. 1cup water (aretesian well water from sandstone) let stand 12hours, mix with 2quarts of sulfuric acid (battery acid), let stand for 24hours stiring every 8 hours to keep the sodium nitrate from hardening and sticking together. i have some pictures but i cannot import them to this email, if you give me an address i can send a regular email to i will send. they dont show much just the 3 diffrent shades of blue and the acumilation of white salts in the bottom.
thanks
huelo the surveyor

 

[lazersteve]

The crystals are likely sodium sulfate or sodium nitrate in the salt saturated solution.

They should rinse out with hot water. Your gold is likely in the crystals structure or at the bottom.

Did everything metal dissolve or it still in there?

Steve

 

[Anonymous]

steve, the first that i did desolved everything, the last one i pulled it before it could. i took one and drained until just a little was left in the bottom and added zinc oxide to the acid and received a color change quickly from the pale blue to a medium to light brown clear(see through) color, with a small amount of dropping (droppings look light grey) i will check again in the morning.
Thanks a bunch for your interest.
huelo

 

[phillips2316]

Don't rule out possibly the scrap wasn't gold at all.
LOL. Lotta copper from the sounds, maybe it was brass to begin with. Steve, would the zinc salt out as white crystals?

Why do you use 70% nitric anyways? Usually most people dilute their 70% nitric with distilled water to help catch some of the NO2 fumes and increase the efficientcy of the nitric acid. Increased molarity would probably be wasteful, violent, and create a lot of heat/fumes.

I think Steve, said it best though, "More Info Please".

Good Luck,
Nick

Happen to know the actual ratio for nitric baths??

 

[Yggdrasil]

Happen to know the actual ratio for nitric baths??

This post was from 2009.
But usually you dilute by 50/50.