I am wondering about something I produced from gold. It looks like a
gold salt, but I'm not sure what I made and I cannot find the answer
nor anyone who seems to know. I would appreciate it if anyone reading
this could help me out.
Here's what I did:
I made up a mix of 100 ml of 60% nitric acid, and 100 ml of 30%
hydrochloric acid, so basically I used a 2 parts nitric to 1 part
hydrochloric 'aqua regia like' mix.
I then put a 0.5 g piece of 24k pure gold into it, and added about 5
ml of 30% H2O2.
I let this react and dissolve in a covered glass for a few days.
The first day while the gold was dissolving this resulted in a light
green solution, but it quickly darkened and became a golden yellow.
After a week I checked again and all the gold was dissolved.
It did not smell much of chlorine nor did it have the smell of nitric
acid. I assume much of the chlorine might have evaporated or sublimed
I then extracted the gold from the solution. I took some diethyl
ether, added about 5 ml to the solution with a glass pipette, stirred
it in, then transferred the whole mix to a HDPE bottle and shook it
well. I then poured the contents back out into a new glass and let the
ether seperate on top of the gold solution. The gold solution was now
a very faint pale-yellow, and the ether a nice golden yellow,
indicating I assume that the gold (HAuCl4 should normally have gotten
formed) did get dissolved into the ether.
I took the ether layer off with a glass pipette and let it evaporate
in a seperate glass vessel.
When almost all of the ether was evaporated off, I added vinegar to
it. I used store bought 8° alcohol vinegar, and added to it until I
had a solution of about 150 ml. I got no reaction. The solution was
still a golden yellow.
I then heated the glass for a few minutes. This did produce a little
bit of a smell of chlorine and ether, but nothing else.
I then let this cool and set it apart, but put an infraredlamp to it.
I am not sure of the heat it produced, but I'm estimating it was
When checking the glass again after about 20 minutes, I noticed I got
some white crystals on the bottom of my glass. They looked like a
cross between tiny snowflakes and salt crystals. There were also a few
of them settling down out of the solution.
I let this continue for about an hour, and noticed it built up.
I was curious what this was, so I decided to try to isolate whatever
this stuff that precipitated was.
I took a syringe and sucked most of the golden-yellow colored vinegar
off, but when I got to only a few ml's left I seemed to be disturbing
the white stuff at the bottom with the syringe's sucking action, so I
I then decided to add distilled water to it and stir it up. The
solution looked pretty clear with a faint hint of pale yellow. The
white stuff looked like white silky threads when stirred up. It did
not seem to want to settle down again, not even after letting it stand
for two hours. It might have fallen out of solution again after a few
days, but I tried something else.
I added a ml of 30% H2O2 to this.
I got no initial reaction, but when checking again after 10 minutes I
noticed tiny gold particles all throughout the solution and the white
fluffy stuff was gone.
I assume the H2O2 oxidized the white stuff back to metallic gold,
indicating the white stuff was probably gold and not some contaminant.
Somebody else tried the same with goldiodide. He dissolved some gold
with a KI/I solution, let it evaporate to a yellowish salt, then
redissolved it with distilled water, I, and some 3% H2O2, added some
vinegar to that and heated. At first he got no reaction, then a lot of
purple smoke got generated from the iodine subliming, then he got no
reaction for a while, added some more vinegar, and then after a while
again got purple smoke to sublime along with the white crystalline
snowflakes to settle down out of solution. I'm guessing it looks like
the vinegar caused a reaction that disassociated the I from the gold
and caused it to sublime out.
He also tried it once more by dissolving some gold using iodine
crystals dissolved in 3% H2O2 and vinegar. It produced the same white
The same stuff was produced in very small quantities using peracetic
acid (actually vinegar with hydrogen peroxide added).
What is this white stuff?
Anyone got an idea?
I don't think it's an acetate since according to the solubility rules
I know of all acetates are soluble, and goldacetate is brown.
Since it's insoluble and precipitated out, I think it could be a
hydroxide since these are insoluble as far as I know, or an organic
gold compound formed by a reaction with whatever is present in vinegar
besides acetic acid.
It's interesting that adding an oxidizer for me caused it to fall back
to metallic gold. I wonder however why any excess unreacted H2O2 in
the other person's experiments did not react with any of the formed
white stuff to take it back to metallic gold, because he seems to have
used enough H2O2 to have excess that didn't react with the acetic acid
from the vinegar or iodine.