Would like some chem advise before trying something new.

[OMG]

I want to try using 'dry' chlorine to make gold and silver chlorides and complexing them with NH4Cl to prevent the gold and silver from being able to cement back out on iron. But Id like to run it by those of you who have good chemistry knowledge.
For me its for use on placer concentrates, but it might work for plated parts too (although it would probably dissolve traces of copper too)
So my idea is
- to dissolve NH4Cl in glycerol.
- In another container, mix (ball mill) TCCA(Trichlor) and the placer concentrates. (or coat gold plated parts with TCCA somehow)
- Then put them all into one container, mix and heat.
- Since there is no water, 'dry' chlorine should be generated (TCCA + chloride salt -> chlorine), along with the heat would form AuCl3 and AgCl, but the temperature would not be high enough for the chlorine to affect any iron or copper
- and the ammonium chloride would complex with the gold and silver (making the silver soluble) and prevent cementing by iron (and maybe aluminum, i forget) since iron cant replace the gold in NH4AuCl4. Although if the reaction can be done quickly (ie in a microwave) cementing might not be too much of an issue anyways.

So that's what i would like to try. Before I try it, is there something that is an impossible reaction? Due to my relying on internet for my self learning gold chemistry I'm not to sure of myself. There should be no nitrates formed so I shouldn't have to worry about 'dry' ammonium silver chloride somehow making a fulminate; right?
And is that right that ammonium gold chloride wont be able to be cemented by iron or aluminum? but it could be by zinc and copper and some other metals (that I don't remember)

Thanks all

 

[LittleJohnnyH2SO4]

TCCA and a chloride salt need an acid and water added to effectively generate chlorine.

Heating glycerol leads to decomposition to acrolein. Look it up, it's pretty horribly toxic. TCCA will oxidize glycerol to glyceraldehyde and dihydroxyacetone as well. You might also chlorinate some glycerol to this stuff: http://en.wikipedia.org/wiki/3-MCPD which you *really* don't want around.

Gold and silver are less reactive than iron and copper. Chlorine would attack iron and then copper preferentially. Even so, in the absence of water, it takes a lot of heat to force the reactions.

Are you sure about ammonium tetrachloroaurate being irreducible by iron? Even if this is the case, I think the complex would only form effectively in solution.

Microwave? We are talking about metal here...little tiny bits and scrap with sharp corner for arcs to form.

 

[OMG]

Are you just making stuff up? Some of the stuff you said isn't true so I'm wondering if any of it is.
But I will definitely look up glycerol reactions etc that you mentioned.
I put only tcca and nacl in water and heated it. Chlorine came off. I will try NH4Cl when I am on my next days off to see for sure.
Gold, Silver, and some other metals are attacked by 'dry' chlorine below 120C. For dry chlorine to attack iron or copper the temperature has to be higher - or there has to be water (vapor) present.
And since the temperature is below 120C, acrolein shouldn't form. I'm sure the temp would stay below 100C.
The HCl Cl reaction uses chlorine gas to dissolve gold at room temperature.

 

[Lou]

@OMG

No, he is not making it up, and wow, I do like this new post message box!

@LittleJohnny, good answer.


It is generally INADVISABLE to mix a strong oxidizer (which I will consider TCCA to be) with an organic which is readily oxidized (which I consider glycerol to be, with its three* hydroxyl groups).

 

[OMG]

Ok. Thanks.

I'm downloading a book called handbook of solvents, so maybe that will have something interesting in it that I can use instead of glycerol.
The solvent would have to have the properties:
-boiling point > 120C
-does not react with Cl2 (ie keeps it 'dry' - doesn't generate HCl) -although it would be nice if it could 'hold' the chlorine somehow
-dissolves nh4cl and nh4aucl4
-can be washed free from the solids
-economical (processing ~1% au in concentrates)

I could also just generate the chlorine separately and get it into the mix some other way. Then TCCA won't screw other things up.

Any suggestions on a solvent?

 

[LittleJohnnyH2SO4]

It is generally INADVISABLE to mix a strong oxidizer (which I will consider TCCA to be) with an organic which is readily oxidized (which I consider glycerol to be, with its two hydroxyl groups).

3 hydroxyls, Lou

I suspect the chlorine being evolved by your TCCA and NaCl solution is only utilizing the first and maybe second of the three chlorines on the ring. Hydrochloric acid readily liberates clouds of chlorine and after cooling, cyanuric acid crystallizes out of solution.

As for chlorine in truly dry conditions, you are unlikely to find them, especially in glycerol, which is quite hygroscopic.

The HCl Cl process uses aqueous chlorine gas, so the point is moot.

That is a tall list of characteristics for a solvent to have. You should generate the chlorine gas seperately, which avoids a good deal of hassle since TCCA behaves quite differently than pure chlorine gas and the side reactions can and will make a mess.

Of solvent kinds, many are inadvisable due to the formation of nasties under anything but ideal conditions. Ketones, sulfones, and sulfoxides only need the smallest trace of water to get the reactions started. Ethers (and perhaps alcohols) risk the formation of chloroethers, which bare more than a superficial structural resemblance to mustard gas. You're going to want to minimize light exposure since just about any organic solvent can be chlorinated by the chlorine radicals UV light generates.

 

[lazersteve]

I would stay away from organics of any kind.

Explore various molten salts as the solvent. There are some metal chlorides that decompose to produce chlorine gas also. You may be able to use this to your advantage.

Steve

 

[Oz]

Little Johnny brings up a point I have wondered about, the cyanide portion of TCCA. I like using chlorine and had thought of using an HCl drip over TCCA in a reaction vessel to produce chlorine gas to put into solution with a diffusion rod. What happens with the cyanide portion, is it left in the reaction vessel or destroyed by the heat of the reaction? I’m just pondering the waste stream disposal and possible hazards of this approach.

 

[Lou]

3 hydroxyls, Lou

Come now, you knew that I knew that you knew. Just testin' ya


Anyway, I don't really think there are much of any solvents that really could be useful except maybe solvents like perchloroethylene.


Oz, what is left after that ought to be plain old cyanuric acid.