From: dwilkins@northernnet.com (Don Wilkins)
Newsgroups: sci.chem
Subject: Re: Why are gold and household bleach incompatible?
Date: Sun, 04 Feb 1996 02:15:16 GMT

On 3 Feb 1996 02:24:24 GMT, Rick Hall <rbhall@fix.net> wrote:

>-=Why is it ill-advised to wear gold rings while handling household bleach?

Aside from the fact that you shouldn't be handling household bleach
without protective gloves there is a problem with gold rings.

Gold is soluble in solutions which contain both an oxidizing agent and
chloride ion. Bleach (calcium hypochlorite) has both.

At best your ring will be etched at worst it will be dissolved.

  _               _   _                  Für d' Flöh gibts a Pulver 
 (_|   |   |_/o  | | | |  o              für d' Schuach gibts a Wix, 
   |   |   |     | | | |      _  _    ,   für'n Durst gibts a Wasser
   |   |   |  |  |/  |/_) |  / |/ |  / \_  bloss fuer d' Dummheit gibts nix.
    \_/ \_/   |_/|__/| \_/|_/  |  |_/ \/ 
                                         

From: dwilkins@northernnet.com (Don Wilkins)
Newsgroups: sci.chem
Subject: Re: Why are gold and household bleach incompatible?
Date: Tue, 06 Feb 1996 16:43:34 GMT

On Mon, 05 Feb 1996 20:01:44 -0500, Eric Lucas <lucas@superlink.net>
wrote:

>-=Don Wilkins wrote:
>-=> ...
>-=> Gold is soluble in solutions which contain both an oxidizing agent and
>-=> chloride ion.
>-=
>-=Is this true in the general sense? Anyone have personal experience 
>-=or data with bleach and gold (pure gold)?  I'd always heard that the 
>-=only common material that will dissolve gold is HCl/HNO3.  This of 
>-=course fits the generic description "oxidizing agent and chloride 
>-=ion", but I thought it was the only common example known, not a 
>-=species of a general class.

Whoever you heard that from was wrong.

Would you like another example? Dangle your gold ring in a NaCl
solution so that the ring is connected to a battery so that the gold
is anodic. Place another electrode in the solution and finish
connecting the cell so this electrode is the cathode and watch your
ring disappear. 

Try it again with a solution of NaCN. No ring.
One more time use a bromide solution.

Try placing the ring in a NaCl solution and then experiment with a
variety of oxidizing agents. (H2O2, sodium peroxide, KMnO4, etc.)
Repeat with HCl. If you produce chlorine it is time to remove the
ring. No HCl/HNO3 necessary.

Aside from those examples one can look to the cyanide process for the
extraction of gold. A commercial process using a little cyanide and a
little air or sodium peroxide. 

In addition of course there are a number of metals which will dissolve
gold. Mercury at room temperature but a considerable number of others
at their melting point.

>-=I'm wondering if the problem may be with the other metals (silver? 
>-=copper?) generally present in non-24K gold, like 14K jewelry gold.  
>-=I can believe bleach would dissolve those other metals right out of 
>-=the alloy, leaving a destroyed ring.

No it is not the other metals. Silver e.g. would tend to form a
protective coating if the chloride is not too high. It's the
complexing agent and the oxidizing agent.

>-=I generally like John Huffman's answer better.  I have personal 
>-=experience getting another irritant, methylene chloride, under a 
>-=piece of jewelry or clothing.  Yeeoooowwww!!!!!!!!

I like mine better. Don't work in chemicals without protecting your
hands. Always follow appropriate protective procedures. You can
replace the ring.



  _               _   _                  Für d' Flöh gibts a Pulver 
 (_|   |   |_/o  | | | |  o              für d' Schuach gibts a Wix, 
   |   |   |     | | | |      _  _    ,   für'n Durst gibts a Wasser
   |   |   |  |  |/  |/_) |  / |/ |  / \_  bloss fuer d' Dummheit gibts nix.
    \_/ \_/   |_/|__/| \_/|_/  |  |_/ \/ 

Subject: Re: Au Reaction
From: nreitzel@lonestar.jpl.utsa.edu (Norman L. Reitzel)
Date: Apr 16 1995
Newsgroups: sci.chem

In article <1995Apr16.104647.1@beach.utmb.edu> arussell@beach.utmb.edu writes:

>	Still looking for someone who can fill in this reaction for me :
>
>NaClO + CH3COOH + AU ->
>then the reaction for bubbling SO2 through the solution to precipitate the Au
>out.

This is kind of a strange reaction, and it will go much quicker if you 
add a source of chloride ions to the solution.  Commercial bleach usually 
contains sodium chloride and hypochlorite both.  Without chloride ions, 
the reaction takes an unusual pathway:

  8NaClO + 2Au + 6HC2H3O2  -->  2NaAuCl4 + 6NaC2H3O2 + 3H2O + O2

If you have available free chloride ion, then the reaction takes a more 
mundane course, and is much faster since ClO- doesn't have to oxidize 
water to free oxygen:

  6NaClO + 2NaCl + 2Au + 6HC2H3O2  -->  2NaAuCl4 + 6NaC2H3O2 + 3H2O

By bubbling sulfur dioxide through the solution, the chloroaurate is 
reduced back to metallic gold while the sulfur dioxide is oxidized to a 
plethora of sulfur species including dithionate, S2O6--.  The overall 
reaction is:

  6SO2 + 6H2O + 12NaC2H3O2 + 2NaAuCl4  -->  12HC2H3O2 + 3Na2S2O6 + 8NaCl

In reality, there will be a half-dozen different sulfur species present, 
everything from sulfite to sulfate and all the poly species in the middle.

  ------------------------------------------------------------------------
  Norman L. Reitzel, Jr.       |    "When you live beside the graveyard,
  nreitzel@lonestar.utsa.edu   |     you can't cry for every funeral."
  Blue Water Ventures, dba.    |                     Russian Proverb
  ------------------------------------------------------------------------

Subject: Re: Au Reaction
From: reitzel@lonestar.jpl.utsa.edu (Norman L. Reitzel)
Date: Apr 16 1995
Newsgroups: sci.chem

In article <3mrqfu$4lb@ringer.cs.utsa.edu> nreitzel@lonestar.jpl.utsa.edu (Norman L. Reitzel   ) writes:

>By bubbling sulfur dioxide through the solution, the chloroaurate is 
>reduced back to metallic gold while the sulfur dioxide is oxidized to a 
>plethora of sulfur species including dithionate, S2O6--.  The overall 
>reaction is:

>  6SO2 + 6H2O + 12NaC2H3O2 + 2NaAuCl4  -->  12HC2H3O2 + 3Na2S2O6 + 8NaCl

Uh, <acute embarassment>, that reaction should also include the 
precipitated metallic gold:

  6SO2 + 6H2O + 12NaC2H3O2 + 2NaAuCl4  -->
                12HC2H3O2  + 3Na2S2O6 + 8NaCl + 2Au

Oh well.  Typical chemical consultant.  Run the reaction and keep the 
gold for himself.  Apologies.

  ------------------------------------------------------------------------
  Norman L. Reitzel, Jr.       |    "When you live beside the graveyard,
  nreitzel@lonestar.utsa.edu   |     you can't cry for every funeral."
  Blue Water Ventures, dba.    |                     Russian Proverb
  ------------------------------------------------------------------------