It sounds like a Christmas song that Burl Ives (who?) used to sing,
"Silver and gold, silver and gold..."
The principal behind adding gold is that it is also a soft acid cation
like mercury. Anything mercury might stick or coordinate with, gold
would too. By having the gold in excess, one blocks "sticky sites." In
addition, both Hg and Au are easily reduced, so by having gold in
excess, the Au is more likely to be reduced by any reducing substance
than the Hg. Silver is also a soft acid cation and easily reduced, so
the principal would be the same with certain caveats(!!).
Silver is easily reduced even by exposure to light. I don't know the
procedures that you found, but be aware that as a long term solution
stabilizer, gold would probably be your better choice. Light exposure
catalyzes reduction and precipitation of silver. As the metallic silver
comes out of solution, Hg may amalgamate with it or otherwise stick to
I agree with Duane. Chloride in high concentrations, especially > 1.2 M
(though lower concentrations still help). This takes Hg2+ toward the
[HgCl4]2- complex. By shifting the equilibrium away from free Hg2+ ion,
one shifts the equilibrium away from metallic mercury. Ag, however is
not soluble at some Cl- concentrations. There ARE higher chloro
complexes with Cl- that are soluble, but hitting that without losing any
and keeping it there through dilutions may not be easy. I would stick
with Au, or choose a soluble chelator with a sulfur ligand like
pyrrolidinecarbodithionic acid ammonium salt (APDC) if you want
something other than HCl. APDC requires much less.
R. Steven Pappas, Ph.D.
Emergency Response & Air Toxicants Branch
Centers for Disease Control & Prevention
4770 Buford Hwy. NE, M.S. F-44
Atlanta, GA 30341-3717
[log in to unmask]
From: PLASMACHEM-L: Analytical Chem.(ICP's, DCP's, MIP's).
[mailto:[log in to unmask]] On Behalf Of Michael Murphy
Sent: Tuesday, January 26, 2010 4:57 PM
To: [log in to unmask]
Subject: gold and silver
I have a question regarding stabilizing Hg solutions with silver. I
had good luck with stabilizing Hg solutions with Au (both as chloride
nitrate salts) and in fairly concentrated hydrochloric acid solutions.
However, I have come across a method indicating the use of silver
of gold. I am not familiar with this and have not been able to find a
ready reference. Does anyone have experience with this arrangement?
Always willing to learn something new ....